Cytoplasmic sequestration of the RhoA effector mDiaphanous1 by Prohibitin2 promotes muscle differentiation.

Muscle differentiation is controlled by adhesion and growth factor-dependent signalling through common effectors that regulate muscle-specific transcriptional programs. Here we report that mDiaphanous1, an effector of adhesion-dependent RhoA-signalling, negatively regulates myogenesis at the level of Myogenin expression. In myotubes, over-expression of mDia1ΔN3, a RhoA-independent mutant, suppresses Myogenin promoter activity and expression.

A fine balance: epigenetic control of cellular quiescence by the tumor suppressor PRDM2/RIZ at a bivalent domain in the cyclin a gene.

Adult stem cell quiescence is critical to ensure regeneration while minimizing tumorigenesis. Epigenetic regulation contributes to cell cycle control and differentiation, but few regulators of the chromatin state in quiescent cells are known. Here we report that the tumor suppressor PRDM2/RIZ, an H3K9 methyltransferase, is enriched in quiescent muscle stem cells in vivo and controls reversible quiescence in cultured myoblasts.

The small chromatin-binding protein p8 coordinates the association of anti-proliferative and pro-myogenic proteins at the myogenin promoter.

Quiescent muscle progenitors called satellite cells persist in adult skeletal muscle and, upon injury to muscle, re-enter the cell cycle and either undergo self-renewal or differentiate to regenerate lost myofibers. Using synchronized cultures of C2C12 myoblasts to model these divergent programs, we show that p8 (also known as Nupr1), a G1-induced gene, negatively regulates the cell cycle and promotes myogenic differentiation. p8 is a small chromatin protein related to the high mobility group (HMG) family of architectural factors and binds to histone acetyltransferase p300 (p300, also known as CBP).