MiR-466h-5p induces expression of myocardin with complementary promoter sequences.

A number of studies microRNAs (miRNA) play an important role in cardiac physiological and pathological processes. In these studies, miRNA regulates gene expression by repressing translation or directing sequence-specific degradation of complementary mRNA. Here, we reveal a new regulatory mechanism in the process of cardiac hypertrophy which miRNA may also regulate the promoter activity of target genes. In the course of the study, we find that miR-466h-5p regulates the occurrence of myocardial hypertrophy via myocardin and it can upregulate the expression of myocardin through directly binding to the promoter region of myocardin. Meanwhile, we also find that myocardin can reverse-activate miR-466h-5p expression through binding to the CarG box. Thus, miR-466h-5p and myocardin form a positive regulation loop in the process of cardiac hypertrophy. These findings reveal a new mode by which miRNAs may regulate gene expression and may play a positive role in revealing the complete mechanisms of cardiac hypertrophy.