circSamd4 represses myogenic transcriptional activity of PUR proteins

摘要

By interacting with proteins and nucleic acids, the vast family of mammalian circRNAs is proposed to influence many biological processes. Here, RNA sequencing analysis of circRNAs differentially expressed during myogenesis revealed that expression increased robustly in mouse C2C12 myoblasts differentiating into myotubes. Moreover, silencing , which is conserved between human and mouse, delayed myogenesis and lowered the expression of myogenic markers in cultured myoblasts from both species. Affinity pulldown followed by mass spectrometry revealed that associated with PURA and PURB, two repressors of myogenesis that inhibit transcription of the myosin heavy chain (MHC) protein family. Supporting the hypothesis that might complex with PUR proteins and thereby prevent their interaction with DNA, silencing enhanced the association of PUR proteins with the promoter, while overexpressing interfered with the binding of PUR proteins to the promoter. These effects were abrogated when using a mutant lacking the PUR binding site. Our results indicate that the association of PUR proteins with enhances myogenesis by contributing to the derepression of MHC transcription.