Non-coding RNAs in Gene Regulation
from: Epigenetics (Edited by: Jörg Tost). Caister Academic Press, U.K. (2008)
Recent studies have revealed a surprisingly large number of RNAs transcribed in eukaryotic cells. The majority of them does not function as messenger, transfer or ribosomal RNAs, and are thus called non-coding RNAs (ncRNAs). Although the ncRNAs that have so far been characterized represent only the tip of iceberg, it is becoming increasingly evident that ncRNAs are functionally involved in many biological processes, such as proliferation, differentiation and development. NcRNAs function as regulators of gene expression on various levels, including chromatin modification, transcription, RNA modification, RNA splicing, RNA stability and translation. Among the best studied ncRNAs are small interfering RNAs (siRNAs) and microRNAs (miRNAs). Both of them regulate gene expression through the RNA interference (RNAi) pathway. It is currently estimated that miRNAs account for more than 1 % of predicted genes in higher eukaryotic genomes and up to 30 % of protein-encoding genes are estimated to be subjected to miRNA regulation. MiRNAs and their targets appear to form complex regulatory networks. In addition, miRNAs cooperate with transcription factors to control gene expression. The properties of gene regulatory networks such as feedback loops generated by the combinatorial action of TFs and miRNAs, which facilitate both sustained response and quick transition to stimulation, are beginning to be understood read more ...