Isolamento de cromatina por purificação de RNA (CHIRP)

Biology
JoVE Journal
Biology
AccessviaTrial
 

Summary

CHIRP é uma técnica recente e rápida de mapa genômico sítios de ligação de RNAs não-codificantes longos (lncRNAs). O método tira partido da especificidade dos oligonucleótidos anti-sentido ladrilhos para permitir que a enumeração de sítios lncRNA-bound genómicos.

Cite this Article

Copy Citation | Download Citations | Reprints and Permissions

Chu, C., Quinn, J., Chang, H. Y. Chromatin Isolation by RNA Purification (ChIRP). J. Vis. Exp. (61), e3912, doi:10.3791/3912 (2012).

Please note that all translations are automatically generated.

Click here for the english version. For other languages click here.

Abstract

RNAs não-codificantes longos são os reguladores de cromatina principais estados para processos biológicos importantes, como a compensação de dosagem, imprinting e expressão de genes de desenvolvimento 1,2,3,4,5,6,7. A recente descoberta de milhares de lncRNAs em associação com os complexos de cromatina específicos de modificação, tal como o complexo Repressiva Polycomb 2 (PRC2) que medeia a histona H3 lisina 27 trimethylation (H3K27me3), sugere as funções gerais para lncRNAs numerosos estados na gestão de cromatina em um gene específico moda 8,9. Enquanto alguns lncRNAs são pensados ​​para trabalhar em cis em genes vizinhos, lncRNAs outros trabalhar em trans para regular genes localizados distantes. Por exemplo, Drosophila lncRNAs roX1 e roX2 regiões ligam numerosos no cromossomo X de células masculinas, e são críticas para a compensação de dosagem 10,11. No entanto, as localizações exatas dos seus locais de ligação não são conhecidos em alta resolução. Da mesma forma, humana lncRNA hotair pode afectar PRC2 ocupação em hundreds de genes do genoma 3,12,13, mas como especificidade o objectivo é claro. LncRNAs também pode servir como suportes modulares para recrutar o conjunto de complexos de proteínas múltiplas. O clássico trans-acting RNA andaime é o RNA TERC que serve como o modelo e andaime para a telomerase complexo 14; hotair também pode servir como um andaime para PRC2 e um desmetilase H3K4 complexo 13.

Estudos anteriores de mapeamento de ocupação de RNA em cromatina revelaram percepções substanciais 15,16, mas apenas com um único locus do gene de cada vez. Os locais de ocupação da maioria dos lncRNAs não são conhecidos, e os papéis de lncRNAs na regulação da cromatina foram principalmente inferida a partir dos efeitos indiretos da perturbação lncRNA. Assim como imunoprecipitação de cromatina seguido por microarray ou seqüenciamento profunda (CHIP CHIP ou CHIP-seq, respectivamente) tem melhorado muito a nossa compreensão de interações DNA-proteína em escala genômica, aqui nós ilustrar um Recenqüentemente publicado estratégia para mapear ocupação RNA longo de todo o genoma em alta resolução 17. Este método de isolamento, cromatina pela RNA Purificação (CHIRP) (Figura 1), baseia-se na captura de afinidade de alvo lncRNA: Complexo de cromatina por ladrilhos anti-sentido-oligos, que gera então um mapa de sítios de ligação genómicos com uma resolução de várias centenas de bases com sensibilidade elevada e baixa do fundo. CHIRP é aplicável a muitos lncRNAs porque o desenho de afinidade sondas é simples, dada a sequência de RNA e não requer conhecimento da estrutura do RNA ou domínios funcionais.

Protocol

1. Projeto Sonda

Design DNA anti-senso de lado a lado sondas para a recuperação seletiva de RNA alvo por piar.

  1. Projeto sondas anti-senso oligo usando o designer sonda on-line em singlemoleculefish.com 18.
  2. Use esses parâmetros: número de sondas = 1 / sonda de 100 pb de comprimento RNA, 2) Alvo% GC = 45, comprimento Espaçamento 4) = 60-80; 3) Comprimento Oligonucleotide = 20. Quebre RNA em segmentos se muito tempo para o designer. Omitir regiões de repetições ou homologia extensa.
  3. Ordem sondas anti-senso de DNA com BiotinTEG em 3-primeiro-final.
  4. Sondas etiqueta de acordo com as suas posições ao longo do RNA. Separá-los em dois grupos para que a piscina ", mesmo" contém todas as sondas de numeração 2, 4, 6, etc, e na piscina "estranho" contém sondas de numeração 1, 3, 5, etc Diluir pool de sondas para concentração de 100 mM e armazenar a -20 ° C.
  5. Todas as experiências são para ser feita usandoambas as caixas, que servem como controles internos para o outro. Sinal dependente de ARN real estaria presente em ambos os pools, enquanto sonda específicas ruídos seria único para cada pool. Isto aplica-se tanto para CHIRP-qPCR e CHIRP-seq.

2. Células Colheita

Recolher células que serão usados ​​para a experiência CHIRP.

  1. Crescer as células em placas de cultura de tecidos ou frascos até à confluência. Lavar com salina tamponada com fosfato (PBS) e uma vez trypsinize. Têmpera de tripsina com> volume 2x de mídia, pipeta cima e para baixo para retirar as células e ressuspender em suspensão de células individuais. Transferir todos os meios e as células ressuspensas em tubos de 50 ml Falcon. 20 milhões de células são tipicamente suficiente para uma amostra CHIRP.
  2. Girar em células 800RCF durante 4 min. Meios aspirado e ressuspender 40 milhões de células em 40 ml de PBS, combinar os tubos, se necessário. Girar em células 800RCF durante 4 min. Decantar PBS, aspirar cuidadosamente sobre um ângulo que o líquido restante.
  3. 3. Cross-link células e recolher pellet celular

    Crosslink coletadas células com glutaraldeído para preservar RNA-cromatina interações e preparar pellet celular.

    1. Execute todas as etapas à temperatura ambiente.
    2. Prepare glutaraldeído 1% em PBS à temperatura ambiente. Preparar 10 ml por 10 milhões de células (0,4 ml de caldo de glutaraldeído a 25% + 9,6 mL de PBS). O glutaraldeído deve ser utilizado fresco.
    3. Toque fundo de tubos Falcon de desalojar pelotas. Ressuspender o sedimento de células em glutaraldeído a 1%, começando com um pequeno volume para evitar pedaços, em seguida, o início até ao volume total. Inverta para misturar. Reticulação durante 10 min à temperatura ambiente num agitador de ponta a ponta ou rotador.
    4. Extingue-se a reacção de reticulação com um volume de 1/10th de 1,25 M de glicina, à temperatura ambiente durante 5 min.
    5. Girar em 2000RCF durante 5 min. Aspirar o sobrenadante e lava-pelete com 20 mL de PBS gelado uma vez, girando a 2000RCF durante 5 min.
    6. Aspirar e ressuspender o wincinerada, reticulada pelete com 1 ml de PBS, refrigerada por 20 milhões de células. Transfira cada ml a um tubo Eppendorf e giram a 2000RCF durante 3 min a 4 ° C. Remover PBS, tanto quanto possível, com a ponta da pipeta com cuidado.
    7. Flash-congelar os peletes de células em azoto líquido e armazenada a -80 ° C indefinidamente.

    4. Lise Celular

    Lisar células reticulados para preparar lisado celular.

    1. Descongelar sedimentos celulares congelados à temperatura ambiente. Toque difícil desalojar e misturar o pellet celular. Girar para baixo o sedimento em 2000RCF durante 3 min a 4 ° C. Use uma forte ponta da pipeta 10 ul para remover qualquer PBS restante.
    2. Em uma balança eletrônica (precisão de 1 mg) tara de um tubo de Eppendorf vazio (os nossos tubos de pesar 1.060 gramas muito consistente). Pese cada pellet e gravar o seu peso. Um prato centímetros completa 15 de células HeLa reticulados tipicamente pesa 100 mg.
    3. Tampão de Lise suplemento (massa 10X de pellet, por exemplo, 1 ml para 100 mg) com fresh inibidor da protease, PMSF e Superase-in (veja a lista de tampão em anexo). Misture bem.
    4. Adicionar 10X volume de Tampão de Lise completado, para cada tubo e ressuspender o sedimento. Para as pelotas pequenas <25 mg, ressuspender em 250 ul de tampão de lise suplementado. Suspensão deve ser suave. Se não, dividir suspensão em 500 uL alíquotas e usar uma motorizada pelete misturador para quebrar grumos. Proceder de imediato à sonicação.

    5. Sonicação

    DNA de cisalhamento por sonicando lisados ​​de células reticuladas.

    1. Sonicar lisado celular em Bioruptor em 15 tubos Falcon ml. Use <1,5 lisado ml em cada tubo, e para mais rapidamente sonicação, sonicar não mais do que dois tubos de cada vez.
    2. Sonifique em um banho de água 4 ° C a mais alta definição com 30 segundos, 45 segundos OFF intervalos de pulso. Verifique lisado cada 30 min. Continuar sonicando até que o ligado celular não é mais turvo. Isso pode demorar tão pouco como 30 minutos e até 4 horas. O númerode tubos, o volume da amostra, a temperatura do banho, eo período de tempo de sonicação irá afectar o tempo que o processo leva. Tubos provavelmente sonicar em taxas diferentes, de modo juntam-los em conjunto a cada 30 min e redistribuir em tubos originais para assegurar a homogeneidade. Nota: o glutaraldeído-reticulado células demorar muito mais para sonicate do que seus equivalentes de formaldeído.
    3. Quando lisado transforma claro, transferir 5 uL lisado para um novo tubo Eppendorf. Adicione 90 uL de DNA de proteases K (PK) Buffer (ver lista buffer) e 5 PK uL. Vortex para misturar e girar rapidamente. Incubar durante 45 min a 50 ° C.
    4. Extrair DNA com Qiagen kit de purificação PCR. Eluir o DNA em 30 uL Tampão eluição Qiagen (EB) e verificar o tamanho do DNA em 1% gel de agarose. Se grandes quantidades de DNA é o esfregaço 100-500 pb, sonicação está completa. Se não, continuar a sonicate.
    5. Centrifugue as amostras sonicadas em 16100RCF durante 10 min a 4 ° C. Combine sobrenadantes, alíquotas em amostras de 1 ml e congelar-in Flash nitroge líquidon. Armazenar a -80 ° C.

    6. CHIRP

    Hibridizar sondas de DNA biotiniladas para o RNA e isolar cromatina ligada.

    1. Tubos de descongelamento de cromatina à temperatura ambiente.
    2. Preparar o tampão de hibridação (ver lista de buffer, prepare 2 ml por ml de cromatina). Vórtice para misturar.
    3. Para uma amostra CHIRP típico usando 1 ml de lisado, remover 10 uL para RNA INPUT e 10 uL de ADN para INPUT e local em tubos de Eppendorf. Manter em gelo até posterior utilização.
    4. Transferir 1 cromatina mL a 15 mL tubo Falcon. Adicionar 2 mL Tampão de Hibridização a cada tubo. Para o volume total <1,5 ml, utilizar tubos Eppendorf.
    5. Descongele sondas à temperatura ambiente. Nanodrop sondas para verificar quantidade se você não tê-lo usado em um longo tempo (100 sondas iM deve especificação ~ 500-600 ng / ul usando configuração DNA de cadeia simples). Adicionar volume apropriado de sondas específicas para os tubos (100 pmol por sonda 1 mL da cromatina, 1 uL de 100 sonda pmol / uL por 1 mL de cromatina).Misture bem. Incubar a 37 ° C durante 4 horas com agitação.
    6. Com 20 min restante para a hibridação, preparar os grânulos C-1 magnéticos (armazenada a 4 ° C). Use de 100 L por 100 pmol de sondas. Lava-se com 1 mL Tampão de Lise não suplementado três vezes, utilizando a tira de íman DynaMag-2 a esferas separadas a partir de tampão.
    7. Contas Ressuspender em volume original de tampão de lise e Suplemento com PMSF fresco, PI e Superase-in. Após 4 h de reacção de hibridação está completa, adicionar 100 grânulos uL a cada tubo. Misture bem. Incubar a 37 ° C durante 30 min com agitação.
    8. Preparar tampão de lavagem (5 mL por amostra). Vórtice para misturar. Pré-aquecido a 37 ° C. Adicionar PMSF antes da utilização.
    9. Lavar grânulos com 1 mL de tampão de lavagem por cinco vezes. Na primeira lavagem, utilizar-15 DynaMag tira magnética a esferas separadas, decantar, e ressuspender em 1 mL de tampão de lavagem. Transferir volume para tubo Eppendorf de 1,5 mL. Incubar a 37 ° C com agitação durante 5 min.
    10. Em lavagens subseqüentes, girar cada tubo em um minicentrifuge, Definir amostra em DynaMag-2 tira magnética durante 1 min. Decantar amostra, seque os pingos com um Kimwipe, ressuspender em 1 ml de tampão de lavagem. Incubar a 37 ° C com agitação durante 5 min. Repetir para cinco lavagens totais.
    11. Na última lavagem, ressuspender as esferas bem. Retirar 100 uL e reserve para o isolamento de RNA. Reserve uL 900 para fração de DNA. Coloque todos os tubos em DynaMag-2 fita magnética e remover o tampão de lavagem. Gire todos os tubos para baixo brevemente; colocá-los na faixa ímã. Retire o último pedaço de tampão de lavagem completamente com uma afiada ponta de pipeta 10 ul.

    7. RNA Isolation

    Extrair fracção de ARN a partir de amostras Chirp para quantificar por qRT-PCR.

    1. Tome 100 l amostras de contas e 10 amostra de entrada uL RNA. Adicionam-se 85 uL RNA tampão pH 7,0 PK para o RNA INPUT. Contas Ressuspender em 95 uL de RNA PK pH 7,0. Adicionar 5 K Proteinease uL e incubar a 50 ° C durante 45 min com ponta a ponta de agitação.
    2. Resumidamente girar todos os tubos eferver amostras durante 10 min em bloco de aquecimento a 95 ° C.
    3. Arrefeça amostras em gelo, adicionar 500 uL TRIzol vórtice, vigorosamente, durante 10 seg. Incubar a temperatura ambiente durante 10 min. Conservar a -80 ° C ou vá para a etapa 4.
    4. Adicionar 100 uL de clorofórmio para TRIzol amostras tratadas. Vortex vigorosamente durante 10 seg. Girar em 16100RCF numa centrífuga de bancada durante 15 min a 4 ° C.
    5. Remover ~ 400 uL sobrenadante aquoso, evitando orgânica e de interface.
    6. Adicionar 600 uL (1,5 de volume) de etanol a 100% e misturar bem. Centrifugue a amostra através MIRNeasy colunas mini. Lave 1x com ERP (MIRNeasy mini-kit), 2x por RPE com o protocolo do fabricante. Eluir com 30 uL sem nuclease H2O (NFH 2 O).
    7. Tratar o produto de eluição com a DNA-RNA livre por protocolo do fabricante. Após a reacção está completa, aquecer a amostra durante 15 minutos a 65 ° C para inactivar qualquer completamente DNase restante.
    8. Use 1 RNA isolado por microlitro bem para qRT-PCR para confirmar lncRNArecuperação. GAPDH é frequentemente utilizado como um controlo negativo.

    8. Isolamento de DNA

    Extrair DNA de amostras de fração Chirp para identificar por seqüenciamento ou quantificar por qPCR.

    1. Preparar o tampão de eluição DNA (ver lista de buffer), 150 ul por amostra, incluindo entrada DNA.
    2. Adicionar 1 0μL RNase A (10 mg / mL) e 10 uL de RNase H (10 U / ul) por ml de tampão de eluição de DNA, e vórtice para misturar.
    3. Ressuspender cada amostra de grânulos em 150 uL de Tampão de Eluição com DNA RNases. (Ressuspender ENTRADA DNA em 140 uL) Incubar a 37 ° C durante 30 min com agitação.
    4. Contas separadas e sobrenadante em DynaMag-2 tira magnética. Remover o sobrenadante e adicionar aos tubos etiquetados.
    5. Prepara-se uma segunda alíquota de tampão de eluição de ADN com 10 uL de RNase A (10 mg / mL) e RNaseH (10 U / mL) exactamente como é feito em 8,2). Adicionar 150 uL de cada amostra (incluindo entrada do ADN), incubar e remover o sobrenadante. Colete todos sobrenadante (should ser ~ uL 300).
    6. Adicionar 15 PK uL de cada amostra. Incubar a 50 ° C durante 45 min com agitação.
    7. Pré-girar amarelo tubos fase de bloqueio de gel (5PRIME). Transferir as amostras de DNA a tubos de bloqueio de fase de gel, e adicionam-se 300 uL PhOH: Clorofórmio: isoamilo por amostra. Agita-se vigorosamente durante 10 min, e girar para baixo em uma centrífuga de bancada a 16100RCF durante 5 min a 4 ° C. Tome aquosa a partir do topo (~ uL 300). Adicionar 3 GlycoBlue uL, 30 NaOAc uL, e 900 uL de EtOH a 100%. Misture bem e armazenar a -20 ° C durante a noite.
    8. Girar amostras a 16100RCF durante 30 min a 4 ° C.
    9. Decante o sobrenadante cuidadosamente. Adicionar 1 mL de EtOH a 70% e vórtice para misturar. Girar em 16100RCF durante 5 min. Remover o sobrenadante com uma pipeta. Deixe secar por 1min. Ressuspender em 30 uL EB.
    10. Amostras de DNA está pronto para análise por qPCR ou preparação de bibliotecas de alto rendimento de sequenciamento por protocolo Illumina.

    10. Os resultados representativos

    A Figura 1 A Figura 2 mostra o enriquecimento de humano telomerase RNA (TERC) a partir de células HeLa sobre GAPDH, um RNA abundantes celulares que serve como um controlo negativo. Maioria dos RNAs TERC (~ 88%) presentes na célula foram puxados para baixo através da realização de CHIRP, enquanto que apenas 0,46% de GAPDH RNA foi recuperado, demonstrando um factor de enriquecimento de ~ 200 vezes. Sondas inespecíficas, tais como sondas de segmentação LacZ RNA, que não se expressa em células de mamíferos (Figura 2), pode ser usado como adicionais controlos negativos.

    Regiões de ADN que se espera que se ligam a lncRNA alvo são tipicamente enriquecida ao longo de regiões negativas, quando medido por qPCR. A Figura 3 mostra qPCR validação de quatro hotair ligados a sítios em fibroblastos de prepúcio humanos primários que determinados através da realização de CHIRP-seq na mesma linha celular, enquanto TERC e GAPDH DNA sítios siRVE como regiões de controlo negativo. Tanto o "mesmo" ea sonda "estranha" define rendeu enriquecimento comparável de espera hotair ligados sites sobre regiões negativas, marca registrada dos verdadeiros lncRNA sítios de ligação.

    Alta capacidade de seqüenciamento de DNA CHIRP enriquecido produz um mapa global de lncRNA sítios de ligação. A Drosophila lncRNA roX2 é conhecido para interagir com o cromossoma X de uma maneira que é necessária para a compensação de dosagem. A Figura 4 mostra roX2 perfil de ligação ao longo de um secção do cromossoma X. Tanto o "mesmo" e "estranha" as amostras já foram seqüenciados e seus ruídos originais foram eliminados para produzir uma faixa de sinais que se sobrepõem. Cada "pico" aqui indica um site de forte roX2 vinculativo. A faixa completa ea lista de roX2 genes alvo têm sido descritas na Chu et ai. 2011 17.

    Figura 1.
    Figura Fluxograma 1. Do procedi CHIRPDure. Cromatina é reticulado para lncRNA: aductos de proteína in vivo biotinilados sondas azulejos são hibridizados para alvejar lncRNA, e os complexos de cromatina são purificados utilizando esferas de estreptavidina magnéticos, seguido por lavagens rigorosas.. Nós eluir lncRNA DNA ligado ou proteínas com um coquetel de RNase A e H. A seqüência lncRNA suposta ligação está esquematizado na laranja. Anteriormente publicado em Chu et ai. 2011. 17

    Figura 2.
    Enriquece a Figura 2. Chirp para o homem TERC RNA. TERC-asDNA sondas recuperar ~ 88% de RNA celular TERC e GAPDH indetectável. LacZ-asDNA sondas são utilizados como controles negativos e recuperar nem RNAs. A média + dp são mostrados. Anteriormente publicado em Chu et ai. 2011. 17

    Figura 3.
    Figura 3. Hotair CHIRP-qPCR em humano primário parafibroblastos Eskin. NFKBIA, HOXD3-4, SERINC5 e ABCA2 são regiões que interagem com hotair. TERC e GAPDH serviram como controles negativos. A média + dp são mostrados. Anteriormente publicado em Chu et ai. 2011. 17

    Figura 4.
    Figura 4. CHIRP-seq de dados de roX2 RNA em células de Drosophila SL2. "Mesmo" e "estranho" foram seqüenciados em separado; seus dados mesclar para refletir apenas picos comuns em ambos. A faixa fundida é mostrado. Anteriormente publicado em Chu et ai. 2011. 17

Discussion

Aqui descrevemos CHIRP-seq, um método de mapeamento em sites in vivo lncRNA ligação do genoma. Os principais parâmetros para o sucesso são as piscinas de divisão de azulejos sondas de oligonucleotídeos e reticulação glutaraldeído. A concepção de sondas de afinidade é simples, dada a sequência de RNA e não requer conhecimento prévio da estrutura do RNA ou domínios funcionais. O nosso sucesso com roX2, TERC, e hotair - três RNAs bastante diferentes em duas espécies - sugere que CHIRP-seq provavelmente generalizáveis ​​para lncRNAs muitos. Tal como com todas as experiências, os controlos de cuidados e adequada são necessários para interpretar os resultados. LncRNA diferente pode exigir titulação de condições, ea mudança criteriosa de condições, tais como seleção de sondas diferentes de afinidade ou reticuladores, pode realçar diferentes aspectos da RNA-cromatina interações. Como ChIP seguintes, nem todos os eventos de ligação são, necessariamente, funcional, e estudos adicionais são necessários para verificar as conseqüências biológicas da RNA occupancy em cromatina. No entanto, prevemos muitas aplicações interessantes desta tecnologia para os pesquisadores de outros cromatina associados lncRNAs, cujo número agora na casa dos milhares 8,9. Assim como ChIP-seq abriu a porta para a exploração do genoma de interações DNA-proteína, CHIRP-seq estudos do "RNA interactoma" pode revelar muitos novos caminhos da biologia.

Disclosures

C. Chu e Chang HY são nomeados como inventores sobre um pedido de patente com base neste método.

Acknowledgments

Agradecemos T. Hung, MC. Tsai, O. Manor, E. Segal, M. Kuroda, T. Swigut, e I. Shestopalov para as discussões. Apoiado pela Agência de Ciência, Tecnologia e Pesquisa de Cingapura (CC), NIH-R01 e R01 CA118750-HG004361 (HYC), e do Instituto de Medicina Regenerativa da Califórnia (HYC). HYC é um cientista de carreira precoce do Howard Hughes Medical Institute.

Materials

Name Company Catalog Number Comments
Buffer List:
Dissolve a pellet of complete protease inhibitor in 1 ml water as 50x stock. Make 100 mM PMSF in isopropanol (100x stock). Superase-in is used as 200x stock. Store all at -20 °C.
Lysis Buffer:
50 mM Tris-Cl pH 7.0
10 mM EDTA
1% SDS
Always add PMSF, P.I. and Superase-in fresh before use except when washing beads
Proteinase K Buffer (for DNA)
100 mM NaCl
10 mM TrisCl pH 8.0 (For RNA use pH 7.0)
1 mM EDTA
0.5% SDS
Add 5% by volume Proteainse K (Ambion AM2546 20 mg/ml) fresh before use
Hybridization Buffer
750 mM NaCl
1% SDS
50 mM Tris-Cl pH 7.0
1 mM EDTA
15% formamide (store in the dark at 4 °C)
Always add PMSF, P.I. and Superase-in fresh before use
Wash Buffer
2x NaCl and Sodium citrate (SSC) (diluted from 20x SSC Invitrogen stock)
0.5% SDS
Always add PMSF fresh before use
DNA elution Buffer
50 mM NaHCO3
1% SDS
Table of specific reagents and equipment:
Glutaraldehyde (EM grade) Sigma-Aldrich G5882-10x10ml
Motorized pellet mixer VWR international V8185-904
Protease inhibitor Roche Group 11873580001
PMSF Sigma-Aldrich 78830
Superase-in Ambion AM2696
Bioruptor Diagenode UCD-200
Falcon tubes (for sonication) Corning 430790
Proteinase K Ambion AM2546
PCR purification kit Qiagen 28106
C-1 magnetic beads Invitrogen 65002
PMSF Sigma-Aldrich P7626-25G
DynaMag-15 magnet Invitrogen 123-01D
DynaMag-2 magnet Invitrogen 123-21D
MIRNeasy mini kit Qiagen 217004
Rnase H Epicentre Biotechnologies R0601K
Rnase A Sigma-Aldrich R4875-100MG
Phase Lock Gel Heavy 5 PRIME 2302810
Trizol Invitrogen 15596-018
Phenol:chloroform:Isoamyl Invitrogen 15593-031
Chloroform Ricca RSOC0020-1C
GlycoBlue Ambion AM9515
Glycine JT Baker 4057-06
PBS, pH 7.4 Invitrogen 10010-049
Elution Buffer (EB) Qiagen 19086
20x SSC Invitrogen 15557-036
10% SDS Invitrogen 15553-027
DNA-free Ambion AM1906
Buffer kit Ambion AM9010
Formamide Invitrogen 15515-026

DOWNLOAD MATERIALS LIST

References

  1. Koziol, M. J., Rinn, J. L. RNA traffic control of chromatin complexes. Curr. Opin. Genet. Dev. 20, 142-148 (2010).
  2. Mercer, T. R., Dinger, M. E., Mattick, J. S. Long non-coding RNAs: insights into functions. Nat. Rev. Genet. 10, 155-159 (2009).
  3. Rinn, J. L. Functional demarcation of active and silent chromatin domains in human HOX loci by noncoding RNAs. Cell. 129, 1311-1323 (2007).
  4. Zhao, J., Sun, B. K., Erwin, J. A., Song, J. J., Lee, J. T. Polycomb proteins targeted by a short repeat RNA to the mouse X chromosome. Science. 322, 750-756 (2008).
  5. Kelley, R. L. Epigenetic spreading of the Drosophila dosage compensation complex from roX RNA genes into flanking chromatin. Cell. 98, 513-522 (1999).
  6. Pandey, R. R. Kcnq1ot1 antisense noncoding RNA mediates lineage-specific transcriptional silencing through chromatin-level regulation. Mol. Cell. 32, 232-246 (2008).
  7. Wang, K. C. A long noncoding RNA maintains active chromatin to coordinate homeotic gene expression. Nature. 472, 120-124 (2011).
  8. Khalil, A. M. Many human large intergenic noncoding RNAs associate with chromatin-modifying complexes and affect gene expression. Proc. Natl. Acad. Sci. U.S.A. 106, 11667-11672 (2009).
  9. Zhao, J. Genome-wide identification of polycomb-associated RNAs by RIP-seq. Mol. Cell. 40, 939-953 (2010).
  10. Meller, V. H., Wu, K. H., Roman, G., Kuroda, M. I., Davis, R. L. roX1 RNA paints the X chromosome of male Drosophila and is regulated by the dosage compensation system. Cell. 88, 445-457 (1997).
  11. Franke, A., Baker, B. S. The rox1 and rox2 RNAs are essential components of the compensasome, which mediates dosage compensation in Drosophila. Mol. Cell. 4, 117-122 (1999).
  12. Gupta, R. A. Long non-coding RNA HOTAIR reprograms chromatin state to promote cancer metastasis. Nature. 464, 1071-1076 (2010).
  13. Tsai, M. C. Long noncoding RNA as modular scaffold of histone modification complexes. Science. 329, 689-693 (2010).
  14. Zappulla, D. C., Cech, T. R. RNA as a flexible scaffold for proteins: yeast telomerase and beyond. Cold Spring Harb. Symp. Quant. Biol.. 71, 217-224 (2006).
  15. Nagano, T. The Air noncoding RNA epigenetically silences transcription by targeting G9a to chromatin. Science. 322, 1717-1720 (2008).
  16. Carter, D., Chakalova, L., Osborne, C. S., Dai, Y. F., Fraser, P. Long-range chromatin regulatory interactions in vivo. Nature. 32, 623-626 (2002).
  17. Chu, C., Qu, K., Zhong, F. L., Artandi, S. E., Chang, H. Y. Genomic Maps of Long Noncoding RNA Occupancy Reveal Principles of RNA-Chromatin Interactions. Mol. Cell. (2011).
  18. Raj, A., van den Bogaard, P., Rifkin, S. A., van Oudenaarden, A., Tyagi, S. Imaging individual mRNA molecules using multiple singly labeled probes. Nat. Methods. 5, 877-879 (2008).

Comments

84 Comments

  1. hi,i has a great interest on CHIRP and your works are highly appreciated,but i want to know that where can i find the buffer list?thank you

    Reply
    Posted by: tang n.
    May 5, 2012 - 4:16 AM
  2. Hi there, thanks for the interest in our paper. As you pointed out the original article lacked the buffer list, which we have uploaded a while ago. Hope it helps!

    Reply
    Posted by: Ci C.
    December 18, 2012 - 5:20 PM
  3. Hello, I'm trying to perform ChIRP experiments and your protocol is very helpful to me.

    However, I have a question about the final concentration of biotinylated probes and the volume of the beads.
    My probes are 100µM so 1µL corresponds to 100pmol. I have 50 probes and my question is : should I use 100µL of magnetic C1 beads per 100pmol of probe, so in my case, 50 probes x 100µL = 5mL of beads ?

    Thanks a lot for the answer ?

    Reply
    Posted by: Sylvain F.
    October 31, 2012 - 4:47 AM
  4. I also have this question!

    Reply
    Posted by: Guihai f.
    November 28, 2012 - 7:51 AM
  5. Hi guys, thanks for the interest in our paper. That's indeed a common question I get, so apologize for not explaining that more clearly in the paper. The 100uM concentration refers to all probes, so if you have ² probes in the pool the individual concentration is 50uM per probe, and if you have 50 probes it's ²uM per probe. It follows that as you scale up number of probes in the pool you do not have to scale up the amount of beads to add. As a caution though, we have noticed that when I use too many probes the concentration of each probe drops too much and it actually adversely affects yield. Try not to use more than 50 probes if possible.

    Reply
    Posted by: Ci C.
    December 18, 2012 - 5:23 PM
  6. what is the fucntion of the Buffer kit ? I can not find it in the protocol.

    Thanks for your time!

    Reply
    Posted by: Guihai f.
    November 1, 2012 - 12:50 AM
  7. The buffer kit is simply a convenient collection of buffers provided by Ambion that includes 5M NaCl, 1M Tris, 0.5M EDTA, etc..

    Reply
    Posted by: Ci C.
    December 18, 2012 - 5:25 PM
  8. Hi, I refer to your paper in HOTAIR ChIRP. You used 48 oligo probes for this ncRNA. I am trying to do a HOTAIR ChIRP. I am wondering if the number of probes can be smaller to reduce cost without a huge compromise on specificity. Furthermore, I am not doing sequencing but a specific check on a genomic region of interest, so I supposed the background noise may be lower? Thank you!

    Reply
    Posted by: Yi Fang L.
    November 8, 2012 - 5:11 AM
  9. We share your desire to reduce number of probes used. In preliminary testing I've found that you can use as few as 1 probe per ²00 nucleotide of RNA target RNA. But that number has to be doubled considering if you need both "even" and "odd" set, so effectively tiling density is 1 probe / 100nt.

    Reply
    Posted by: Ci C.
    December 18, 2012 - 5:28 PM
  10. Hello,
    I enjoyed your paper very much.

    At the end of the video, and in the figure, you mention that in this process you can isolate RNA binding proteins that were associated with the RNA. My questions are: have you had success in doing this? What is the protocol for isolating the proteins? Do you just isolate the protein fraction from the Trizol, or is there a more specialized method? Is there a paper that may lay out use of this method?

    Thank you for your help.

    Reply
    Posted by: Gavin J.
    January 18, 2013 - 12:09 PM
  11. Hi,
    Great protocol. Just one question. You mention that all ChIRP steps have to be performed at 37C. I can imagine this is important for the hybridisation steps, but I was wondering why this was needed for the washing steps as well?

    Many thanks

    Reply
    Posted by: Sebastian V.
    March 15, 2013 - 10:21 AM
  12. The washing should be performed at 37C just like you would wash a northern blot at elevated temperatures. If this is logistically difficult for you, just warming up the buffer to 37C and washing on a room temp. shaker works well too.

    Reply
    Posted by: Ci C.
    March 15, 2013 - 1:47 PM
  13. Hello,
    Thanks for the detailed and very helpful protocol. Can you tell me what kind of DNA yields to expect from the pull down per input cell amount? I know it will depend on the lncRNA targeted, but I need an idea of what kind of amounts to expect. Could you tell me what you got for your HOTAIR hybridizations? My own hybs only result in a few nanograms of DNA, and I don't know how to determine whether that is nonspecific DNA binding to my beads or whether it is actual lncRNA-bound DNA? How do you control for this? Thank you for your help in advance.

    Reply
    Posted by: blake e.
    March 20, 2013 - 5:44 AM
  14. Hi,

    Congrats for setting up such a protocol. It might have been discussed already but I would like to have an idea about the typical amounts of DNA and RNA that one might expect from 20 x 10 ^6 cells. This of course is transcript specific, but should we expect nanograms, picograms for either DNA and RNA?

    Also have you tried FA instead of glutaraldehyde for x-linking? Many thanks for your time

    Reply
    Posted by: Antonis A.
    November 26, 2013 - 12:15 PM
  15. Hi,

    Thanks for the detailed protocol. I am about to embark on it over the next week or so and had a question regarding the sonication. You advise a Bioruptor for this step however we only have a Covaris available. Would that provide acceptable sonication and do you have any advice regarding appropriate settings?

    Thank you

    Joshua

    Reply
    Posted by: joshua b.
    March 2, 2014 - 12:24 AM
  16. Yes Covaris works, we've found that it generally reduces sonication time by 30-50% compared with Diagenode. Actual time and intensity needs to be optimized for each machine and cell line.

    Reply
    Posted by: Ci C.
    March 3, 2014 - 5:51 PM
  17. Hi,

    Thanks for the detailed protocol. I am about to embark on it over the next week or so and had a question regarding the sonication. You advise a Bioruptor for this step however we only have a Covaris available. Would that provide acceptable sonication and do you have any advice regarding appropriate settings?

    Thank you

    Joshua

    Reply
    Posted by: joshua b.
    March 2, 2014 - 6:32 AM
  18. To all interested ChIRPers, hybridization can be performed overnight instead of 4hours. Doing so greatly reduces hands-on time. Happy ChIRPing!

    Reply
    Posted by: Ci C.
    March 3, 2014 - 8:14 PM
  19. Hi Ci,

    I have one more issue to resolve regarding ChIRPseq that I would appreciate your input on please (or other ChIRPers that have had similar problems).

    We have been unable to produce lysates using glutaraldehyde despite following the protocol to the letter and getting the Sigma brand that is recommended. Even before sonication, the DNA is degraded to a thick band below 200bp. When we try exactly the same process but substitute 1% formaldehyde (which we normally use for ChIP and 3C) or even plain PBS, the DNA is fine. We have even tried doing everything on ice and reducing the centrifuge steps to only 500g but to no avail.

    My questions therefore are:

    1/ Has your team had similar issues with glutaraldehyde in the past or found it to behave quite differently to formaldehyde (apart from needed longer sonication and harder centrifuging)?
    2/ Though you have shown glutaraldehyde to give a better signal to noise ratio, could we still expect to get usable data using 1% formaldehyde or is it not worth the time and effort?

    Thank you for your time

    Joshua Betts

    Reply
    Posted by: joshua b.
    April 16, 2014 - 8:07 AM
  20. Dear Joshua,

    Thanks for your interest in our protocol. It's unfortunate to hear that you're experiencing DNA degradation. We've never experienced this issue, nor have we heard similar problems from our collaborators who successfully did ChIRP. Usually we're more concerned with RNA integrity, naturally, and if you're careful that's not a problem either.

    Could you tell me how you're extracting DNA, especially prior to sonication?

    Regarding alternative crosslinking methods, for certain lncRNAs we've found that strong formaldehyde crosslinking also works (3% for 30min is a good starting point). 1% formaldehyde usually does not work.

    Best,
    Chu

    Reply
    Posted by: Ci C.
    April 16, 2014 - 1:55 PM
  21. Dear Chu,

    Thank you for your advice - I will try the protocol again but substitute 3% formaldehyde for the glutaraldehyde. Does that require any other adjustments apart from slower centrifuge spins and shorter sonication times?

    In regards to my DNA isolation, I lysed the cells as per the protocol and then treated with proteinase K for 45mins (at 50deg or 65deg - either seemed ok). I then RNAse treated the sample and either phenol chloroform extracted the DNA or instead used the Qiagen PCR columns before running the product on a 1% agarose gel. The columns gave more of a smear on the gel, whilst the phenol chloroform extraction just had a broad band below 100bp.

    When I performed exactly the same procedures on formaldehyde treated cells, I obtained a bright band of gDNA at the top of the gel as well as a more faint diffuse band below 100bp. This is what we normally see when working with formaldehyde. Am I right to expect a strong band of genomic DNA on the gel when using glutaraldehyde before sonication, or does the glutaraldehyde break the gDNA down during the fixation process? Does your glutaraldehyde fixed sample normally start as a broad smear even prior to sonication?

    Our group has a lot of experience with ChIPseq, 3C and 4Cseq library preparation but we have never dealt with glutaraldehyde before so are unsure what to expect.

    Any further suggestions would be greatly appreciated.

    Thanks

    Joshua

    Reply
    Posted by: joshua b.
    April 24, 2014 - 9:26 AM
  22. Before preparing your ChIRP library for sequencing, do you check your DNA size distribution (for example using Agilent Bioanalyzer). If so, do you see a similar distribution to that seen for a typical ChIP sample (200-800 bp range)?

    Reply
    Posted by: Eric S.
    August 29, 2014 - 2:43 PM
  23. Dear Chu
    I have two questions:
    1.In designing your chirp oligos have you tried to reduce the spacer between biotin-oligonucleotides. Is there any steric reason for choosing 1 probe / 100nt?
    2. Did you tried to crosslink adherent cells directly on plate? we have problem in properly resuspend our differentiated murine myoblasts in PBS+glutaraldehyde.

    thanks in advance
    regards

    Mariangela

    Reply
    Posted by: Mariangela M.
    October 16, 2014 - 9:56 AM
  24. Dear Mariangela,

    1. It's both a cost consideration (fewer probes are cheaper) and also a biochemical noise consideration (more probes introduce higher chances for probe:DNA direct hybridization).

    2. Yes we've found no difference fixing on plate vs. in suspension. Feel free to pick and choose what works best for you.

    Best,
    Chu

    Reply
    Posted by: Ci C.
    October 17, 2014 - 10:43 PM
  25. Dear ChIRP community,

    We are having problems getting ChiRP peaks with our transcripts. We have tried ChiRPing against 4 different transcripts and for all of them we were able to get very good fold enrichments in the genomic locus of each transcript (on average 50 to 200 x over background) capturing native transcription but we cannot find other binding sites in the genome for any of them. We have good reasons to believe that some or all of our transcripts are chromatin localized and we also know that the signal in the genomic loci is RNA dependent because it is dramatically reduced when we ChiRP after knocking down our transcripts of interest.

    Our transcripts are low in expression, on average 3 to 10 copies per cell. Any ideas as to how can we improve/solve the issue? Is it abundance that is limiting the system? Has anyone experienced/solved something similar?
    We tried the normal protocol, and now we are trying with 3 % FA in parallel to glut. Any suggestions would be very welcomed!

    Antonis

    Reply
    Posted by: Antonis A.
    November 13, 2014 - 5:18 AM
  26. Hi Antonis, I'm afraid the copy number is simply too low. In all of the ChIRP paper published so far I don't think anyone went that low.

    Your enrichment of the genomic loci could be complicated by ChIRP probes pulling down the DNA directly. Do an RNase-control to see if the signal is still there.

    Reply
    Posted by: Ci C.
    November 13, 2014 - 8:52 AM
  27. Dear Chu,

    Thank you for the prompt reply-yes I know that with such expression levels, ChIRP is challenging. I can try the RNase control but as mentioned I am confident about the RNA-dependence of the signal, because it falls back to LacZ levels when I knock down the transcripts. I guess we will have to try increasing the sensitivity of the experiment. Could an increase in x-linking time help here, have you guys tried 20 min of glut x-linking?

    Reply
    Posted by: Antonis A.
    November 18, 2014 - 3:28 AM
  28. Hello,
    I enjoyed your paper very much.

    At the end of the video, and in the figure, you mention that in this process you can isolate RNA binding proteins that were associated with the RNA. My questions are: have you had success in doing this? What is the protocol for isolating the proteins? Do you just isolate the protein fraction from the Trizol, or is there a more specialized method? Is there a paper that may lay out use of this method?

    Thank you for your help.

    Reply
    Posted by: jason h.
    November 26, 2014 - 10:15 PM
  29. Dear ChIRPers, we're happy to announce that you can now officially design and order ChIRP from Biosearch Technologies (Single molecule fish). Scientists developing ChIRP probes using the Stellaris probe designer and following the guidelines from our publication can now email Sheila Semaan at Biosearch Technologies, Inc. for help with ordering the probes in the proper format. Sheila’s contact info is as follows:

    Sheila J. Semaan, Ph.D., Associate Product Manager
    Biosearch Technologies, Inc.
    Email: ssemaan@biosearchtech.com

    Reply
    Posted by: Ci C.
    December 17, 2014 - 9:33 AM
  30. Dear ChIRP community,

    You can soon study RNA-protein interactions in vivo using ChIRP-mass spec. The story is coming out in Cell on April 2nd. Stay tuned!

    Reply
    Posted by: Ci C.
    March 25, 2015 - 5:42 AM
  31. Hello, thank you for the protocol! I also want to perform a RNA pulldown using your protocol and i am very excited for your RNA-protein interaction protocol! I have one question regarding the biotin oligos. Do they need to be 3' biotinylated or can they also be 5' biotinylated. Have you tested this? And you say nothing about (salt, HPLC) purification of the oligos. Thanks for answering my questions.

    Reply
    Posted by: Christine C.
    March 30, 2015 - 10:01 AM
  32. and is it necessary to order Biotin-TEG oligos or is "standard" biotin sufficient?

    Reply
    Posted by: Christine C.
    March 30, 2015 - 11:33 AM
  33. Hi Christine, thanks for your interest in our technique. Regarding your questions:

    1) 3' biotinylation is preferred, because oligos are synthesized 3' to 5'. This way, we ensure all oligos start with a biotin tag. 5' biotin tags are usually added to a synthesized oligo, and that increases the chance of untagged probes, which is less than ideal. However if you can ensure high tagging efficiency on 5' end, and the cost is advantageous, I don't see why it won't work!

    2) We use a disposable reverse phase column called "Glen-Pak DNA purification cartridge," which is a very efficient and cost-effective system. These are really short DNA probes and HPLC or PAGE would be necessary (also probably can't tell tag from untag probes).

    3) TEG ensures no steric hindrance, I don't have hard evidence on this but I think it's necessary.

    Reply
    Posted by: Ci C.
    March 30, 2015 - 10:03 PM
  34. Thank you for your answers! As I am performing your protocol with the aim of an RNA-protein pulldown, i have some other questions regarding the protocol, if you don't mind.

    - in the protocol before washed your magnetic beads in unsupplemented lysis buffer and you blocked the magnetic beads using BSA and yeast RNA- in the latest protocol you don't block. Why is that?

    - ChIRP-MS requires 100 Mio cells, ChIRP-seq 20 Mio cells. If i want to perform ChIRP-MS (or western blot) do i need 100 pmol of probe for each 20 Mio cells --> 500 pmol of probe for ChIRP-MS? --> 500 µl beads(??)

    Reply
    Posted by: Christine C.
    April 8, 2015 - 8:12 AM
  35. Hi Christine,

    - We no longer block as there's no difference in results, and we prefer a more streamlined protocol. BSA would also potentially contaminate ms results.

    - yes scale up beads accordingly. We do 1ml beads per experiment routinely. It gets expensive, but hopefully you'd only have to do it once or twice, and validate with western in a smaller scale later. For western of more abundant chirp hits, I do from 1/5 of cell pellets, but for less abundant ones I still use full amount.

    Reply
    Posted by: Ci C.
    April 8, 2015 - 11:36 PM
  36. Dear ChIRPers,

    ChIRP mass spec has just come online today at Cell. We're very pleased to introduce a very robust and straight-forward method that's optimized to study lncRNA:protein interactions. Check out the story at:

    http://www.cell.com/cell/abstract/S0092-8674(15)00312-8

    Happy ChIRPing!

    Best,
    Chu

    Reply
    Posted by: Ci C.
    April 2, 2015 - 9:00 PM
  37. Dear ChIRPers,

    Now you can easily design and order ChIRP probes with the latest optimization from Biosearch Technologies, the company that invented Single Molecule FISH.

    https://www.biosearchtech.com/chirpdesigner/

    Best,
    Chu

    Reply
    Posted by: Ci C.
    April 2, 2015 - 10:24 PM
  38. Hi, i'm trying to perform ChIRP-western and i have some questions concerning the methods.

    1) for a control, i also want to see if my RNA is present: how can i get a small aliquot of post-ChIRP beads to perform RNA elution with this aliquot
    2) for the protein biotin elution buffer: resuspend beads in what volume?
    3) for ChIRP-MS lysates are incubated with 30µl beads - can i reuse them?

    thank you in advance!

    Reply
    Posted by: Carolin C.
    April 14, 2015 - 7:18 AM
  39. Hi Carolin,

    thank you for your interested in our method.

    1) yes that's what we we as well. Simply take a 1% or 10% aliquot of your post-wash beads, and extract RNA.

    2) that's dependent on your starting beads volume. But there's a practical constraint, you don't want to have so much volume that after addition of TCA will exceed the capacity of an eppendorf tube.

    3) I'm not sure if I understand your question. Reuse lysate or beads?

    Reply
    Posted by: Ci C.
    April 15, 2015 - 12:20 AM
  40. thank you for the answers!
    to 2) again: if my beads are 100µl starting volume - so i resuspend 2x in biotin elution buffer and pool. Is 2x100µl then enough? and then add 25% of 100%TCA (50µl)?
    to 3) my question is, if i reuse the beads in the hybridization step. and just add another 70 µl beads (=100µl beads)

    Reply
    Posted by: Carolin C.
    April 24, 2015 - 11:23 AM
  41. so what do you recommend for my previous questions 2) and 3)

    another question: how do you calculate the amount of RNA retrieved? I retrieve only 10% of my RNA of interest calculated as % of Input. Furthermore,when i took a sample of what hasn't bound (after hybridization and capture of the beads) i get only 15% (fraction of washing doesn't include much RNA). so where has my RNA gone? i repeated several times… degradation?

    Reply
    Posted by: Carolin C.
    May 20, 2015 - 5:13 AM
  42. Hi, Carolin
    I am also, using ChiRP. Can you tell me the equation you used to calculate the % of your retrieval

    thanks

    Reply
    Posted by: u.
    June 28, 2016 - 1:22 AM
  43. Hi Carolin, May I ask in the end with your 10-20% retrieval rate of RNA, can you identify new proteins by MS via UV crosslink? Thanks.

    Reply
    Posted by: Zhenqiu H.
    May 17, 2018 - 6:20 PM
  44. Dear ChIRPers, we're glad to introduce the Magna ChIRP kit from Millipore. It's a simple pre-made reagent set for scientists who prefer the reliability and user-friendliness of a reputable brand.

    https://www.emdmillipore.com/US/en/product/EZ--Magna-ChIRP-RNA-Interactome-Kit---Isolation-and-characterization-of-non-coding-RNA%3Achromatin-complexes,MM_NF-17-10495

    Happy ChIRPing!

    Best,
    Chu

    Reply
    Posted by: Ci C.
    April 15, 2015 - 12:35 AM
  45. Hi Chu

    Thanks for sharing this information.
    Did anyone try this kit already and how good is it? Kits are easy to use and save time for reagents.

    Reply
    Posted by: Liu Z.
    April 16, 2015 - 5:17 PM
  46. Dear Chu,

    Many thanks for your excellent protocol. I'm designing a probe set and have been looking at the probes you designed for HOTAIR and XIST for inspiration. I noticed that some of the probes designed for XIST target the sequence at multiple loci (e.g. Probe 10), albeit ocassionally with a single base mismatch. Either way, I assume this may reduce the number of probes needed. Could I ask whether this was a deliberate design strategy and, if so, does the Biosearchtech ChIRP designer incorporate this strategy?

    Thanks

    Reply
    Posted by: Sebastian V.
    April 16, 2015 - 11:31 AM
  47. Dear Chu

    I feel exciting when I am reading your chirp paper in molecular cell. I have 2 questions that need your input.

    1) Have you or others you know tried in vivo tissue samples and if so how it works? I realized that your molecular cell and the latest cell paper used cell lines primarily.

    2) If I have a non-coding RNA which is 400 bp alone, and cannot generate more than 8 probes based on the parameters provided by https://www.biosearchtech.com/chirpdesigner/ ? What should I do ? Could I just reduce the spacer length between odd and even probes ? do you think it will increase background due to the increased probe density?

    Thanks

    Zhiyong

    Reply
    Posted by: Liu Z.
    April 16, 2015 - 4:49 PM
  48. Hi Zhiyong,

    Thank you for your kind words about our paper. Regarding your questions:

    1) Yes we have ChIRPed in drosophila tissues with great success. The key is probably to have small enough chunks of tissue that can be crosslinked effectively and thoroughly.

    2) Email the Biosearchtech team and they can help you manually reduce the number of probes.

    Good luck!

    Best,
    Chu

    Reply
    Posted by: Ci C.
    May 22, 2015 - 11:15 PM
  49. hey there, i was able to retrieve RNA with your method, but i'm not retrieving RNA bound protein (even though i did see a milky pellet after TCA and acetone treatment). i cross link with UV but the other steps i perform are just the same you are doing.
    i'm not so sure about this competetive elution method by using free d-biotin - and do you no longer add protease inhibitors in your buffer? the beads are simply eluted by using biotin buffer, rotate sample for 20 min,RT and 10 min mixing at 65°C (x2). This is it? then everything should be in my buffer and i continue with TCA precipitation ON.
    sorry if i this sounds stupid to you. i'm just looking for mistakes i could have made...

    Reply
    Posted by: Carolin C.
    June 10, 2015 - 10:32 AM
  50. Hi Carolin, I'm glad you're able to get RNA yield, that's a very good sign. The reason that you're not getting proteins could be: 1) mass spec instrument not sensitive enough. The quality of your results varies A LOT with who runs your mass spec. We've had amazing experience with Bill Lane at Harvard. 2) UV cross linking is known to be super low yield. Unless your lncRNA is very abundant or you're prepared to start with a huge amount of material, I would suggest formaldehyde as your first step. 3) TCA and cold acetone with give you a tiny pellet no matter what (the detergent acts as a carrier that will precipitate by itself even in the absence of proteins). So unless you see a sizable pellet, the presence of a pellet itself doesn't mean anything. d-biotin elution is complete, assuming you're using the C1 beads and biotin from invitrogen. Protease inhibitors are absent at the elution step, because your solution should be quite pure and free of contaminating proteases at that point assuming good lab practice. Hope this helps!

    Reply
    Posted by: Ci C.
    June 10, 2015 - 5:45 PM
  51. hey ci! thank you for your answers!
    1) i'm doing western blot as a start, later on i will do mass spec - so thank you for your tip&hint! as i already know a 100% candidate to get retrieved with my (cytoplasmic) mRNA, i stained for this candidate and got no result.
    2) you also mentioned uv-crosslinking in your first protocol, do you have a comment or any experience on the time of cross linking or amount of joules? so far i cross linked 150mj/cm^2 but I'm thinking to increase that. also i need to scale up my cells/beads/probe as you're saying. i do not know if formaldehyde cross linking works in my case, as i have cytosolic mrna.
    3) yes I'm using c1 dynabeads and d-biotin from invitrogen! thanks for the explanation, that helps!

    thank you very much for your quick answers, tips and hints!

    Reply
    Posted by: Carolin C.
    June 11, 2015 - 8:43 AM
  52. hey there, repeated the experiment - this time i used 200 Mio MEF cells - 10 ml lysate and 1 ml beads, 10µl probe. i also increased cross linking to 300 mj/cm^2 - still no proteins (known RNA binding protein) detectable via western blot. i confirmed RNA pulldown via qPCR after cross linking from a small fraction of beads.
    is sonication necessary?
    any troubleshooting ideas?

    Reply
    Posted by: Carolin C.
    June 17, 2015 - 11:38 AM
  53. I would start with formaldehyde first. UV is known to cross link very inefficiently, and certain residues of contact may not be amenable to photocrosslinking at all. Yes sonication is necessary to soluble the cell lysate.

    Reply
    Posted by: Ci C.
    June 19, 2015 - 2:37 PM
  54. i'm using your 25%TCA / Aceton precipitation method to precipitate my proteins. Have you also experienced a pH change (when adding laemmli it turns green/yellow) due to rest TCA? And i think i don't get my pellet resuspended - even after mixing and resuspending. Isn't boiling for 30 min, 95°C destroying the proteins?

    Posted by: Carolin C.
    July 10, 2015 - 7:30 AM
  55. Yes I have had similar experiences before: pH change usually can be prevented by more careful and thorough acetone washes (although need to care not to disturb pellet), and over drying will cause difficulty in resuspension. I never air dry for over a minute. Boiling is completely fine. Try using the LDS samples buffer / Bis-tris gel system from invitrogen, these work great on chirp samples. If you are still having issues with pH, you can manually adjust a little with a moderate alkaline buffer.

    Posted by: Ci C.
    July 10, 2015 - 10:59 PM
  56. Hi Carolin,

    I've the same problem as you had. I could only retrieve 10-15% of RNA when compare to input RNA. Could you please share how you sort this problem?

    Thank you in advance!

    Reply
    Posted by: Ganeshkumar A.
    July 23, 2015 - 4:25 AM
  57. Hi Ganeshkumar, unfortunately i didn't solve the problem… but i found more RNA of interest in my beads when i directly resuspended them in trizol (leaving out proteinase K treatment) - since i'm interested in my proteins bound to the RNA the proteinase K treatment step is of no importance to me. But so far i still couldn't retrieve my RNA bound proteins.

    Reply
    Posted by: Carolin C.
    July 23, 2015 - 5:19 AM
  58. Hi Carolin,

    Thanks for your immediate reply. I'll also avoid Proteinase K step and try again.
    I've one more question. We always do two step RT-qPCR. So, the amount of RNA that I retrieve isn't enough to perform a RT reaction. How do you do your RT-qPCR? This question maybe a bit stupid, but i really wanna sort out all the issues as early as possible.

    Thanks in advance.

    Reply
    Posted by: Ganeshkumar A.
    July 23, 2015 - 5:27 AM
  59. Hello,
    my RNA amount is also quite low, measured by Nanodrop (Once i measured with qubit and could't get anything). I'm using max. volume possible for RT reaction and adapt for input, not bound… Then i perform qPCR with my cDNA

    But i suppose you cannot skip proteinase K step when your lysate is formaldehyde treated, or you need to boil it first to reverse the crosslink. i diluted my beads in trizol when i had non-crosslinked samples to check for retrieval percentage

    Posted by: Carolin C.
    July 23, 2015 - 7:12 AM
  60. We always do a one-step qRT-PCR (i.e. each qPCR well runs it's own RT). This in my hands is much more sensitive and convenient as well (you don't have to measure RNA or cDNA, just load equal portions of each sample). We use Strategene Brilliant II SYBR reagents and Roche 480 machine. Let me know if this helps with yield detected.

    Posted by: Ci C.
    August 4, 2015 - 8:32 AM
  61. Hi Ci,

    I did gene specific cDNA synthesis with 10ng of RNA from all conditions and treated with RNase H and A (in excess) and then proceeded to qPCR. This worked good for me and I'm getting around 14-25 fold enrichment in my odd and even probe samples when compared to input.

    Thank you and Carolin for your suggestions.

    Posted by: Ganeshkumar A.
    August 4, 2015 - 10:43 AM
  62. Hello,
    i have not yet retrieved any RNA bound protein, so i'm thinking about what issues to sort out. i have to say i can retrieve my RNA of interest (but only max. 20% of input)

    i'm wondering about the protein amount in your formaldehyde cross linked, sonicated and hypotone lysed cell lysats. I experienced the protein amount (measured with Bradford) to be 5-8 fold lower compared to uncross linked or Uv cross linked cells treated with a NP40 lysis buffer.
    Why is that, and will it affect my experiments? Any ideas why the protein amount is so low?
    Thank you in advance!

    Reply
    Posted by: Christine C.
    July 23, 2015 - 5:47 AM
  63. Hi Christine, off the top of my head the two main reason for less protein detected upon cross linking is 1) insufficient sonication, and 2) insufficient reverse cross linking (i.e. boiling). Regarding 1), you have to titrate sonication time of your lysate, and pick the minimum sonication required to release all proteins and RNA of interest. To test this, precipitate the lysate post sonication for 10 min at max speed, and run qRTPCR against your RNA of interest and western against the protein on both the supernatant and pellet, the latter resuspended in appropriate buffer. This way you'll know if there's anything left to be solubilized. 3% cross linked lysates can take significantly longer to solublized than your typical ChIP cross linking.

    Regarding 2), do no less than 30min boiling in sample buffer. I've titrate that also, and 10min or 20min recovers much less protein.

    Let me know if these help and let's start from here. Good luck!

    Reply
    Posted by: Ci C.
    August 4, 2015 - 8:29 AM
  64. Hello,
    Many thanks again for this superb protocol. I'm currently trying to optimise this for mRNA pull-down from fixed cells. I've tried various fixing conditions in parallel and dot-blotted for my RBP of interest vs a non-binding protein (GAPDH) after performing ChIRP. I found that 1% glutaraldehyde (10 min) samples blotted strongly for my RBP, but produced an equally strong signal for GAPDH. The latter was also the case for 3% formaldehyde (10 min), but blots of both GAPDH and my RBP weren't as strong. The only sample that showed a slightly stronger signal of the RBP vs GAPDH was 1% formaldehyde (10 min), but both signals were quite weak. All samples were sonicated for several 30 sec ON and 45 OFF cycles at maximum intensity before foaming to produce sheared RNA of <500 bp in optically clear samples.

    I tested the expression of mRNA of interest in samples pulled down with my tiling oligo set compared with a run using non-targeting scrabled oligos. A capture on unfixed cells produced a very high target yield in the tiling oligo sample and no mRNA in the scrambled control sample. However, performing the same pull down in the 1% formaldehyde-fixed+sonicated samples dramatically increased background (GAPDH mRNA) compared to the scrambled control. I'm curious if you found anything similar during the development of ChIRP and ChIRP-MS and if you might have any solutions? Would extra sonication perhaps help?

    Many thanks

    Sebastian Vencken PhD
    Post-Doctoral Researcher

    Reply
    Posted by: Sebastian V.
    September 13, 2015 - 8:06 PM
  65. Hi Sebastian,

    Have you had any luck adapting this technique to mRNA capture?

    Best,
    Mike

    Reply
    Posted by: Michael K.
    December 7, 2016 - 4:48 PM
  66. Mixed results to be honest. We went forward with 1% formaldehyde and tried different forms of sonication (incl. covaris which didn't give us effective fragmentation). Biased background was still an issue and the copurification of our RBP (Ago+miRNA) was much lower than expected. This has apparently successfully been performed before (https://www.ncbi.nlm.nih.gov/pubmed/23325846) but we didn't manage to reproduce these results for our target.

    Reply
    Posted by: Sebastian V.
    December 8, 2016 - 4:15 AM
  67. Thanks for the feedback. Does your miR-CATCH work well/better? Similar idea, no sonication, and probes attached to beads first. Have you ever tried to use this to look for bound proteins?

    I also ran across this mRNA pulldown from yeast (https://www.ncbi.nlm.nih.gov/pubmed/27641505). They also attached the oligos to the beads first, but the buffers look more like ChIRP.

    Reply
    Posted by: Michael K.
    December 8, 2016 - 11:44 AM
  68. We've had some pretty good results (and publications) from miR-CATCH, but have also discovered that the performance can be very dependent on both the target and oligo design.
    With thorough optimisation we managed to reduce background in miR-CATCH, but each target was a new challenge in this respect.

    We hoped that ChIRP would significantly reduce the issue of background, but we have found balancing fragmentation and signal to be difficult. Dot blots for Ago2 gave us very high background signal in scrambled controls when using gluteraldehyde, while 1% formaldehyde gave some better signal differentiation, but at reduced strength. If I'd take ChIRP further for mRNA:RBP(:miRNA) capture, I'd look at the sonication and fixing steps again as there may be further room for improvement. Unfortunately, I've moved to other things for now.

    Reply
    Posted by: Sebastian V.
    December 9, 2016 - 10:42 AM
  69. Hello!

    Many thanks for the detailed protocol, however i am having trouble at crosslinking and sonication steps! I am sorry if it sounds silly but I just want to identifiy what I am missing/doing wrong.

    In the near future, I want to scale up for ChIRP MS, however first want to get these steps right as CHIRP MS would consume 10 times the beads.

    Crosslinking - When I add Glycine to quench formaldehyde, it doesnt change color?

    Sonication - As used by your team, I am using Bioruptor to sonicate the Hela S3 lysate (20 Mi. cells/1ml supplemeted lysis buffer) in 15 ml falcon (Corning) with a probe attached to the cap. I cant seem to get a clear lysate as shown in your video. I have tried sonicating starting from 30 cycles to 300 cycles and it just froths towards the end. After centrifugation to remove cell debris, the lysate is still considerably cloudy.

    I see that a lot of people are working on optimising this method and would appreciate any tips / tricks that might help me get going.

    Looking forward to some suggestions.

    Best regards,
    Minakshi
    PhD Student

    Reply
    Posted by: Minakshi G.
    September 30, 2015 - 5:06 AM
  70. Hi Minakshi, thanks for your interest in our protocol. Re your questions:

    - glycine doesn't change the color of formaldehyde, just glutaraldehyde.
    - check our bioruptor to make sure power is normal and probes are centered correctly. It shouldn't take more than a couple hours even for hardy cell lines. Frosting is strange and indicates to me that you may not be centering the probe correctly and thus losing efficiency.

    Reply
    Posted by: Ci C.
    November 2, 2015 - 2:46 PM
  71. Hi,
    I would have a question regarding the usage of formamide. My concern is that once the bottle is opened and the
    formamide is exposed to oxygen, it will begin to oxidize to formic acid. Do you take any precautions to prevent oxidation? How do you store formamide for further use? Sigma suggests to purge formamide with nitrogen and store it frozen to prevent oxidation.

    Thanks a lot for your help.

    Best wishes,
    matjaz

    Reply
    Posted by: Matjaz B.
    November 2, 2015 - 4:53 AM
  72. Hi Matjaz, thank you for your interest in our technique. formamide is indeed subject to oxidation and ionization. Re-deionization is laborious, so we tried our best to protect the reagents by parafilming around the bottle cap after each use and store it at 4C. I usually run through a 1 liter bottle in a year with repeated opening and closing, and have not observed any effect on results over time. Hope this helps.

    Reply
    Posted by: Ci C.
    November 2, 2015 - 2:44 PM
  73. Hello,

    I have another technical question. Even though our probes are very specific (we detect target RNA using different probes with high specificity), we have problem with high DNA background signal. Have you also had a similar problem? One way to resolve the issue would be to pre-clear lysates with beads before the hybridisation step. Have you ever implemented this step? If yes, have you done the pre-clearing in lysis buffer with or without hybridisation buffer?

    Many thanks,

    - matjaz

    Reply
    Posted by: Matjaz B.
    November 3, 2015 - 7:36 AM
  74. Hi Ci,

    Thanks for providing such an excellent protocol. I have a question about probe design. The 3' half of lncRNA I interested in (5kb in length) was fully cover by repeat elements. Because ChIRP probe Designer ignored the repeat sequence when designing probe, I found almost no probe target to the 3' half of this lncRNA. I'm afraid that I will miss all proteins bind to the 3' end of lncRNA if I only use the probe target to the 5' end of lncRNA. I wonder how do you handle lncRNA contains large number of repeat sequence?

    Thanks for any help.

    Sincerely,
    Jian-You

    Reply
    Posted by: Jian-You L.
    December 3, 2015 - 9:48 PM
  75. Hi all!

    Thank you for sharing this protocol!
    I have just analysed the RT-qPCR results coming from the RNA samples in order to analyse the lncRNA retrieval and I have retrieved a very small percentage of the lncRNA. From the input and the ChIRP samples I have used the same volume of sample (for the qPCR, around 36ng for the input and 21g for the ChIRP) and I have obtained a Ct of 30 for the input and 37 for the ChIRP measuring my lncRNA of interest. How do you normalise the results? Do you use the same volume or ng of the different RNA samples? Do you use a normalisation method similar to the ChIP one? https://www.thermofisher.com/uk/en/home/life-science/epigenetics-noncoding-rna-research/chromatin-remodeling/chromatin-immunoprecipitation-chip/chip-analysis.html

    Thank you in advance

    Isabel

    Reply
    Posted by: Isabel R.
    December 17, 2015 - 9:30 AM
  76. Hi, Isabel
    we experience along time to optimize the protocol in our lab around 9 month for lncRNA and we found the result unstable for different lncRNAs but for your normalization we usually use a normalized methods like Chip experiment for both GAPDH and our target,
    Hope that helps
    for more contact amr@mail.ustc.edu.cn

    Reply
    Posted by: u.
    December 8, 2016 - 7:17 PM
  77. Dear Chu:
    Recently I'm trying to perform ChIRP experiments and your detailed protocol is very helpful. However, I have some questions about cell lysis and sonication.
    1. I find that the supplemented lysis buffer cannot lyse the crosslinked cells. The crosslinked cells are only resuspended, after a few minutes they will sink to the bottom of the tube, is it normal?
    2. You emphasize that lysis buffer should be added fresh Protease Inhibitor, PMSF and Superase-in then proceed immediately to sonication after resuspended smooth, however, a sample will be added appropriate supplemented lysis buffer in proportion then devided into several parts to sonicate by limiting ultrasound equipment, and will it be affected?
    3. I only have a Covaris available for sonication in lab, I tried many times but could not find an appropriate setting. My DNA size distribution is normally a bright band of gDNA at the top, a bright band above 2000bp and a diffuse band from 2000bp to 100bp, if I continued to sonicate, the diffuse band would below 100bp, and there were considerably cloudy after centrifuged the sonicated samples. I want to know what and how much influence if DNA smear is less than 100bp or more than 500 bp? Do you have any advice regarding it?
    Looking forward to some suggestions, thank you in advance!
    Best regards
    mixue
    Ph.D. Student

    Reply
    Posted by: he j.
    July 17, 2016 - 3:37 AM
  78. Dear Dr CHU.
    First of all, sorry for my english, but I'm french.
    I work on lncRNA and I really appreciate your two articles on ChIRP and Chirp-MS, and since some months I try to set it up, but unfortunately without result until now.
    => I designed the probes as you know but my lncRNA is about 2.3kb so i was able to design only 26 probes. I also ordered your Positive and Negative Control.
    => I amplified the cells until 200 to 300 million and I cross linked them with 3% formaldehyde 30min and stop it with Glycine 0.125M 5 to 10 min, as you mention.
    => My sonication was tested in order to have a smear of DNA between 100 and 600bp and it took between 120 and 140min. I use a Bioruptore in cold room and I have to change water and ice every 15min in order to maintain the low temperature. Samples are centrifuged and debris are removed.
    => I use 2 to 3 aliquots of 1mL of lysed cells for each test, and the indicated quantity of probes. Of course before incubation, samples are pre-incubated with prewashed beads.
    => First incubation is done at 37 ° C in a shaking system, overnight. Second incubation (after addition of the prewashed beads) is done at 37 ° C for 1 hour.
    => Wash is done 5 times with wash buffer, then samples are eluted (using elution buffer freshly prepared with Sigma-Aldrich Biotine) and precipitated with TCA and Aceton. Pellet are directly dissolved in Laemmli, incubated 30min at 95°C and loaded with 12% acrylamide gel. After 1h at 200V the gel is stained with Coomassie Blue and destained 3 times 45min.
    I found NO BANDS even with Positive and negative controls, but after elution, when I checked the presence of my lncRNA in the sample selected with my probes, the result is positive.

    Could you tell me what are the possible mistakes that I could do ....?
    Thanks a lot.

    Reply
    Posted by: Sebastien C.
    January 3, 2017 - 5:02 AM
  79. Dear Dr. Chu,

    Good day! I am Anchilie, a PhD student, and I am really interested in applying your discovered technique in plants. I am currently doing the ChiRP-MS in Arabidopsis but I don't seem to get any RNA-bound proteins in my sample.

    I would just like to briefly tell you how I do the ChiRP-MS in plants. First, I harvest 3g of 14-day old seedlings and crosslinked it with 1% formaldehyde. From these, I then do nuclear extraction and do sonication. From the 1mL sonicated chromatin, I dilute it with 2mL of hybridization buffer, add 1ul probe and 100ul of beads and incubated then in 37C for O/N or 4 hours at 37C. From then I wash the beads 5x and precipitated the proteins using the biotin elution buffer and TCA method. The samples in 1x Laemmli buffer were submitted to LC/MS. I also check the enrichment in the qPCR and are enriched by 500-fold. However, upon analyzing my samples, the mass spec results only detected mitochondrial and chloroplastic proteins in the control and non-coding RNA

    I also tried many things like using 3% formaldehyde and UV crosslinking. I also did direct boiling of beads in Laemmli buffer. I also tried increasing the amount of material 10x accompanied with increasing the probe and the beads.
    But it doesn't really help.

    I would really appreciate to receive some feedback from you and your group with this matter.

    Best regards,
    Anchilie

    Reply
    Posted by: Anchilie M.
    February 27, 2017 - 4:49 AM
  80. Dear Anchilie,

    I am doing CHIRP in arabidopsis, you are the only only doing CHIRP as far as I know. I met some problems. I couldn't enrich my non coding RNA. So I want to know how did you do your CHIRP? Could you please share your protocol with me? Thanks!

    Reply
    Posted by: Zhi-Hong L.
    June 19, 2017 - 7:56 AM
  81. Hi guys, can anyone help me how the percentage calculation for lncRNA retrieval is done.

    Thank you

    Reply
    Posted by: Sunil B.
    June 22, 2017 - 3:58 PM
  82. Hi,

    Thank you for sharing this protocol, I have a question. If I want to study the potential interaction between a protein and a long non coding RNA in rDNA locus (or eventually with the rDNA directly), do you think that your kit will work ?
    Thank you for your answer

    Reply
    Posted by: Burette M.
    April 12, 2018 - 3:27 AM
  83. Dear professor,
    Thank you for sharing this protocol! It helps me a lot. I have a question to ask. Since ultrasound may break the hydrogen bond, I want to ask whether it is necessary to perform sonication when I study weak RNA-RNA interaction, for example: lncRNA-miRNA interaction?

    Reply
    Posted by: Zihao L.
    May 26, 2018 - 10:52 PM
  84. Dear professor,

    Any idea if using a probe-based sonication (like the Branson sonifier) would work? Anyone has tried it ?
    in the previous lab, we were using the bioruptor however we don't have it where I am now unfortunately and needed help to optimize it on the Branson or probe-based sonifiers?

    Thanks

    Reply
    Posted by: Anonymous
    March 1, 2020 - 4:26 AM

Post a Question / Comment / Request

You must be signed in to post a comment. Please sign in or create an account.

Usage Statistics