SRF and miRs in smooth muscle differentiation and proliferation (Homo sapiens)

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Smooth muscle cells exhibit a unique plasticity, in that they are able to oscillate between proliferative and more quiescent, differentiated states. Their status is governed, in part, by a network of transcription factors, including Klf-4, Elk-1 and SRF, that regulate expression of genes controlling smooth muscle cell state. Two smooth muscle-enriched, co-transcribed microRNAs (miRNAs), miR-143 and miR-145, cooperatively target this transcription factor network to promote smooth muscle cell differentiation. miR-145 also acts in a feed-foward regulatory loop to enhance expression of the smooth muscle regulator, Myocd, which cooperates with SRF to activate transcription of miR-143/145. Conversely, the cardiac and skeletal muscle-enriched miRNA, miR-133, decreased translation of SRF, thereby repressing the smooth muscle cell fate.