The huge world of small RNAs: regulating networks of microRNAs (review).

MicroRNAs (miRNAs) are a recently discovered class of small, non-coding RNAs which do not code proteins. MiRNAs regulate gene expression by inhibiting protein translation from the messenger RNA. MiRNAs may function in networks, forming a complex relationship with diseases. Furthermore, specific miRNAs have significant correlation with diseases of divergent origin. After identification of disease-associated miRNAs, their tissue expression could be altered in a beneficial way by inhibiting or mimicking their effects. Thus, modifying the expression of miRNAs is a potential future gene-therapeutic tool to influence post-transcriptional regulation of multiple genes in a single therapy. In this review we introduce the biogenesis, mechanism of action and future aspects of miRNAs. Research on the post-transcriptional regulation of gene expression by miRNA may reshape our understanding of diseases and consequently may bring new diagnostic markers and therapeutic agents. Therapeutic use of miRNAs is already under clinical investigation in RNA interference trials.