The Pkm duet: Coordinating C2C12 myoblast proliferation and differentiation through Histone 3 phosphorylation and cBAF complex dynamics

Pkm1 and Pkm2 kinases are expressed in differentiating skeletal myoblasts. Knockdown of Pkm1 or Pkm2, therefore, can affect myoblast differentiation, by two independent regulatory mechanisms involving histone phosphorylation and chromatin remodeling complexes. Pkm2 KD in C2C12 cells reduced the chromatin marks of phosphorylated H3-T6, H3-T11 and H3-T45 into several essential myogenic promoters, and consequently, prevented their expression. Also, the transcriptional analysis demonstrated that Pkm2 is required for the expression of the cBAF-specific subunits Dpf2 and Baf250a, which we have previously demonstrated are essential for myogenesis. In contrast, Pkm1 KD alters the localization of nuclear Dpf2 into the cytoplasm as well. Mechanistically, Pkm KD resulted in decreased binding of cBAF components to their myogenic target genes, which also suggested a positive regulation between the cBaf complex and the H3 phosphorylation marks. To investigate the role of Pkm1 or Pkm2 in the regulation for myoblast differentiation, we have performed RNA-seq analysis for C2C12 myoblast stably KD for these kinases targeted using specific shRNA. C2C12 cells stably transfected with non-targeting scrambled shRNA construct were used as controls. Myoblasts were differentiated for 48 h.