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RNA-Binding Proteins for Post-Transcriptional Regulation of Gene Expression
RNA-binding proteins (RBPs) play a key role in post-transcriptional regulation of gene expression by binding to RNA along various points and at various times. In the model of mRNA metabolism, this interaction occurs concurrently or immediately after transcription; as different sets of RBPs bind to the introns and exons of pre-mRNA, through splicing, polyadenylation, mRNA stabilization, nuclear transport, subcellular localization and translation. Since these proteins have the potential to affect the manner and rate of protein synthesis, it is crucial to have a reliable method for identifying and characterizing these RBP/RNA interactions.
ncRNAs in Post-Transcriptional Gene RegulationRecent research on post-transcriptional gene regulation has yielded many new discoveries. Most notably, noncoding RNAs (ncRNAs) have been found to regulate many processes listed above. Especially during development and differentiation, ncRNAs provide a finely tuned mechanism for lineage-specific or even cell-specific protein expression. ncRNAs involved in post-transcriptional regulation include snRNAs, snoRNAs, siRNAs, miRNAs, and piRNAs.
Epigenetics and ncRNAs
Most commonly, ncRNAs downregulate protein expression via silencing, epigenetic changes or translational inhibition. However, ncRNAs can upregulate gene expression through certain chromatin modifications. In eukaryotic cells, miRNAs and piRNAs are the most common small RNAs that mediate gene silencing.
ncRNA-mediated gene silencing (RNAi) is catalyzed by the RNA-induced silencing complex (RISC). RISC is comprised of Argonaute (Ago) proteins and accessory RNAs, and mediates mRNA degradation by complementary small double-stranded RNAs. Specific knockdown of target mRNAs using designed short dsRNA sequences has become a popular genetic tool for analyzing gene function.
At the end of most cell signaling pathways lies a change in gene transcription or posttranscriptional regulation that affects the level or localization of protein expression. Characterization of the regulatory machinery is essential for understanding and potentially modulating biological responses encoded in genomic (and epigenomic) information. In the last decade, a new picture of gene regulatory machinery has emerged, in which transcription, RNA processing, RNA stabilization, RNA export, and even aspects of translational control, are closely coupled with one another.