[Advances in mechanism of small RNAs].

The discovery of RNA interference (RNAi) heralded a revolution in RNA biology. Researchers uncovered 'hidden' layers of regulation of gene expression, in which many previously unidentified families of small RNAs (consisting of approximately 20-30 nucleotides) mediate gene silencing in transcriptional and post-transcriptional levels. In eukaryotes, these small RNAs, including siRNAs, miRNAs, piRNAs, scnRNAs, 21U-RNAs, and some others, regulate gene expression, helping to control cellular metabolism, growth, and differentiation, to maintain genome integrity, to regulate stem cell renewal, and to combat viruses and mobile genetic elements. This review summarizes the current advancement in the identification and biosynthesis of small RNAs and their roles in gene regulation.