pre-rna-splicing-analysis-from-basic-science-to-applied-research

Pre-RNA Splicing Analysis: From Basic Science To Applied Research

ARTICLES DISCUSSED:
Voss, P. G., Haudek, K. C., Patterson, R. J., Wang, J. L. Complementation of splicing activity by a galectin-3-u1 snrnp complex on ...

Universidade De São Paulo (USP)

Universidade de São Paulo

Thyroid cancer is one of the most frequent types of endocrine cancers. In most cases, thyroid cancers are caused by deregulated miRNA expression, especially involving the miR17-92 cluster. miR17-92 transcription is altered in several different tumor types including lymphoma, leukemia, and of the breast and thyroid. As an intronic cluster, miR17-92 must be processed during splicing and therefore interaction between microprocessor and spliceosome machineries is of major importance in understanding its expression.

miR18a and miR19a Recruit Specific Proteins for Splicing in Thyroid Cancer Cells.

The unicellular protists of the group Kinetoplastida include the genera Leishmania and Trypanosoma, which are pathogens of invertebrate and vertebrate animals. Despite their medical and economical importance, critical aspects of their biology such as specific molecular characteristics of gene expression regulation are just beginning to be deciphered. Gene expression regulation also depends on post-transcriptional processing steps, such as the trans-splicing process. Despite being widely used in trypanosomes, trans-splicing is a rare event in other eukaryotes. We sought to describe the protein composition of spliceosomes in epimastigotes of T. cruzi, the etiological agent of Chagas disease. We used two TAP-tagged proteins to affinity purify spliceosomes and analyzed their composition by mass spectrometry. Among the 115 identified proteins we detected conserved spliceosome components, as Sm and LSm proteins, RNA helicases, U2- and U5-snRNP specific proteins. Importantly, by comparing our data with proteomic data of human and T. brucei spliceosome complexes, we observed a core group of proteins common to all spliceosomes. By using amino acid sequence comparisons, we identified RNA-associated proteins that might be involved with splicing regulation in T. cruzi, namely the orthologous of WDR33, PABPCL1 and three different HNRNPs. Data are available via ProteomeXchange with identifier PXD018776.

Proteomic analysis of Trypanosoma cruzi spliceosome complex.

Pre-mRNA splicing is an essential step in eukaryotic gene expression regulation. Genes are composed of exons that remain in the mature mRNAs and intervening sequences named introns. Splicing is the removal of introns and ligation of exons in a mature transcript. Splice site or spliceosome component mutations can lead to different diseases, including neurodegenerative diseases and several cancer types. HuR is an RNA-binding protein that preferentially binds to U- and AU-rich elements, usually found at the 3' UTRs of some mRNAs. We previously observed HuR specifically associated with spliceosomes assembled on introns containing miR-18a and miR-19a. miR-18a and miR-19a are components of the intronic miR-17-92 cluster, along with other five miRNAs. This cluster has been reported to regulate proliferation, migration, and angiogenesis in cells. In this context, we reasoned HuR could be controlling the splicing and processing of these miRNAs, leading to altered cellular phenotypes.

Human Antigen R (HuR) Facilitates miR-19 Synthesis and Affects Cellular Kinetics in Papillary Thyroid Cancer.

Heterogeneous nuclear ribonucleoproteins (hnRNPs) are essential players in the regulation of gene expression. The majority of the twenty different hnRNP proteins act through the modulation of pre-mRNA splicing. Most have been shown to regulate the expression of critical genes for the progression of tumorigenic processes and were also observed to be overexpressed in several types of cancer. Moreover, these proteins were described as essential components for the maturation of some microRNAs (miRNAs). In the human genome, over 70% of miRNAs are transcribed from introns; therefore, we hypothesized that regulatory proteins involved with splicing could be important for their maturation. Increased expression of the miR-17-92 cluster has already been shown to be related to the development of many cancers, such as thyroid, lung, and lymphoma. In this article, we show that overexpression of hnRNP A1 and hnRNP C in BCPAP thyroid cancer cells directly affects the expression of miR-17-92 miRNAs. Both proteins associate with the 5'-end of this cluster, strongly precipitate miRNAs miR-17 and miR-18a and upregulate the expression of miR-92a. Upon overexpression of these hnRNPs, BCPAP cells also show increased proliferation, migration, and invasion rates, suggesting upregulation of these proteins and miRNAs is related to an enhanced tumorigenic phenotype.

Article	Year
miR18a and miR19a Recruit Specific Proteins for Splicing in Thyroid Cancer Cells. Cancer genomics & proteomics\| PubMed ID: 28871004	2017
Proteomic analysis of Trypanosoma cruzi spliceosome complex. Journal of proteomics\| PubMed ID: 32422275	2020
Human Antigen R (HuR) Facilitates miR-19 Synthesis and Affects Cellular Kinetics in Papillary Thyroid Cancer. Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology\| PubMed ID: 35352515	2022
hnRNP A1 and hnRNP C associate with miR-17 and miR-18 in thyroid cancer cells. FEBS open bio\| PubMed ID: 35417090	2022

Patricia Pereira Coltri

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