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In JoVE (1)
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Articles by Lauren P. Blair in JoVE
Lizin demetilaz Faaliyet Kantitatif Ölçümler MassSQUIRM Uygulaması
Lauren P. Blair, Nathan L. Avaritt, Alan J. Tackett
Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences
Biz lisin metilasyon değişiklikleri ölçmek için MALDI kütle spektrometresi ve indirgeyici metilasyon kimya kullanmak için bir yöntem sunuyoruz.
Other articles by Lauren P. Blair on PubMed
Yng1 PHD Finger Binding to H3 Trimethylated at K4 Promotes NuA3 HAT Activity at K14 of H3 and Transcription at a Subset of Targeted ORFs
Molecular Cell. Dec, 2006 | Pubmed ID: 17157260
Posttranslational histone modifications participate in modulating the structure and function of chromatin. Promoters of transcribed genes are enriched with K4 trimethylation and hyperacetylation on the N-terminal tail of histone H3. Recently, PHD finger proteins, like Yng1 in the NuA3 HAT complex, were shown to interact with H3K4me3, indicating a biochemical link between K4 methylation and hyperacetylation. By using a combination of mass spectrometry, biochemistry, and NMR, we detail the Yng1 PHD-H3K4me3 interaction and the importance of NuA3-dependent acetylation at K14. Furthermore, genome-wide ChIP-Chip analysis demonstrates colocalization of Yng1 and H3K4me3 in vivo. Disrupting the K4me3 binding of Yng1 altered K14ac and transcription at certain genes, thereby demonstrating direct in vivo evidence of sequential trimethyl binding, acetyltransferase activity, and gene regulation by NuA3. Our data support a general mechanism of transcriptional control through which histone acetylation upstream of gene activation is promoted partially through availability of H3K4me3, "read" by binding modules in select subunits.
Biochemistry. Mar, 2009 | Pubmed ID: 19256528
Helicases are proteins that unwind double-stranded nucleic acids. Dda helicase from bacteriophage T4 has served as an excellent model for understanding the molecular mechanism of this class of enzymes. Study of the structure of Dda may reveal why some helicases translocate in a 5' to 3' direction on DNA, while others translocate in a 3' to 5' direction. Attaining a structure of Dda has proven difficult because the protein fails to readily form crystals and is too large for current NMR technologies. We have developed a homology model of the enzyme which will serve to guide studies that examine the structural and functional significance of the interaction between Dda and DNA and how this interaction affects translocation and unwinding of DNA. We have tested the structural model by using methods for mapping protein domains and for examining protein surfaces that interact with DNA.
A Noncanonical Bromodomain in the AAA ATPase Protein Yta7 Directs Chromosomal Positioning and Barrier Chromatin Activity
Molecular and Cellular Biology. Sep, 2009 | Pubmed ID: 19581291
Saccharomyces cerevisiae Yta7 is a barrier active protein that modulates transcriptional states at the silent mating locus, HMR. Additionally, Yta7 regulates histone gene transcription and has overlapping functions with known histone chaperones. This study focused on deciphering the functional role of the noncanonical Yta7 bromodomain. By use of genetic and epistasis analyses, the Yta7 bromodomain was shown to be necessary for barrier activity at HMR and to have overlapping functions with histone regulators (Asf1 and Spt16). Canonical bromodomains can bind to acetylated lysines on histones; however, the Yta7 bromodomain showed an association with histones that was independent of posttranslational modification. Further investigation showed that regions of Yta7 other than the bromodomain conferred histone association. Chromatin immunoprecipitation-chip analyses revealed that the Yta7 bromodomain was not solely responsible for histone association but was also necessary for proper chromosomal positioning of Yta7. This work demonstrates that the Yta7 bromodomain engages histones for certain cellular functions like barrier chromatin maintenance and particular Spt16/Asf1 cellular pathways of chromatin regulation.
Epigenetics : Official Journal of the DNA Methylation Society. Apr, 2011 | Pubmed ID: 21273814
In eukaryotes, DNA is wrapped around proteins called histones and is condensed into chromatin. Post-translational modification of histones can result in changes in gene expression. One of the most well-studied histone modifications is the methylation of lysine 4 on histone H3 (H3K4). This residue can be mono-, di- or tri-methylated and these varying methylation states have been associated with different levels of gene expression. Understanding exactly what the purpose of these methylation states is, in terms of gene expression, has been a topic of much research in recent years. Enzymes that can add (methyltransferases) and remove (demethylases) these modifications are of particular interest. The first demethylase discovered, LSD1, is the most well-classified and has been implicated in contributing to human cancers and to DNA damage response pathways. Currently, there are limited methods for accurately studying the activity of demethylases in vitro or in vivo. In this work, we present MassSQUIRM (mass spectrometric quantitation using isotopic reductive methylation), a quantitative method for studying the activity of demethylases capable of removing mono- and di-methyl marks from lysine residues. We focus specifically on LSD1 due to its potential as a prime therapeutic target for human disease. This quantitative approach will enable better characterization of the activity of LSD1 and other chromatin modifying enzymes in vitro, in vivo or in response to inhibitors.
Cancers. Mar, 2011 | Pubmed ID: 21544224
Similar to genetic alterations, epigenetic aberrations contribute significantly to tumor initiation and progression. In many cases, these changes are caused by activation or inactivation of the regulators that maintain epigenetic states. Here we review our current knowledge on the KDM5/JARID1 family of histone demethylases. This family of enzymes contains a JmjC domain and is capable of removing tri- and di- methyl marks from lysine 4 on histone H3. Among these proteins, RBP2 mediates drug resistance while JARID1B is required for melanoma maintenance. Preclinical studies suggest inhibition of these enzymes can suppress tumorigenesis and provide strong rationale for development of their inhibitors for use in cancer therapy.
Loss of the Retinoblastoma Binding Protein 2 (RBP2) Histone Demethylase Suppresses Tumorigenesis in Mice Lacking Rb1 or Men1
Proceedings of the National Academy of Sciences of the United States of America. Aug, 2011 | Pubmed ID: 21788502
Aberrations in epigenetic processes, such as histone methylation, can cause cancer. Retinoblastoma binding protein 2 (RBP2; also called JARID1A or KDM5A) can demethylate tri- and dimethylated lysine 4 in histone H3, which are epigenetic marks for transcriptionally active chromatin, whereas the multiple endocrine neoplasia type 1 (MEN1) tumor suppressor promotes H3K4 methylation. Previous studies suggested that inhibition of RBP2 contributed to tumor suppression by the retinoblastoma protein (pRB). Here, we show that genetic ablation of Rbp2 decreases tumor formation and prolongs survival in Rb1(+/-) mice and Men1-defective mice. These studies link RBP2 histone demethylase activity to tumorigenesis and nominate RBP2 as a potential target for cancer therapy.