MicroRNAs and epigenetics.

MicroRNAs (miRNAs) comprise species of short noncoding RNA that regulate gene expression post-transcriptionally. Recent studies have demonstrated that epigenetic mechanisms, including DNA methylation and histone modification, not only regulate the expression of protein-encoding genes, but also miRNAs, such as let-7a, miR-9, miR-34a, miR-124, miR-137, miR-148 and miR-203. Conversely, another subset of miRNAs controls the expression of important epigenetic regulators, including DNA methyltransferases, histone deacetylases and polycomb group genes. This complicated network of feedback between miRNAs and epigenetic pathways appears to form an epigenetics-miRNA regulatory circuit, and to organize the whole gene expression profile. When this regulatory circuit is disrupted, normal physiological functions are interfered with, contributing to various disease processes. The present minireview details recent discoveries involving the epigenetics-miRNA regulatory circuit, suggesting possible biological insights into gene-regulatory mechanisms that may underlie a variety of diseases.