Human myogenesis is driven by proline-directed kinases and the trans-histone code, H3K9me3/H4K20me3

System-level analysis of the (phospho)proteome during muscle formation and its interplay with epigenetic factors is critical to understand muscular diseases. Using stable isotope labeling (SILAC) and nano liquid chromatography-tandem mass spectrometry (nLC-MS/MS), we analyzed the (phospho)proteome during myogenesis of LHCN-M2 human skeletal myoblast cell line. First, enriched phosphorylation motifs suggested that PKC, cyclin-dependent kinase and MAPK are regulatory kinases during myodifferentiation. Then, we uncovered that the drugs known to inhibit these kinases either promoted myogenesis (PD0325901 and GW8510) or stall differentiation (CHIR99021 and roscovitine). We identified differentiation-specific myogenic and chromatin-related proteins, including histone methyltransferases. We then analyzed histone post-translational modifications (PTMs), and observed regulation of two gene-silencing marks, H3K9me3 and H4K20me3, in a correlated manner with the observed phenotypes. Chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR) confirmed that H3K9me3 is erased from the myogenic regulatory factors (MRFs) MyoD, MyoG and Myf5 in differentiating myotubes. Together, our work demonstrates that the integration of histone PTM, phosphoproteomics and full proteome analysis gives a comprehensive understanding of the close connection between signaling pathways and epigenetics during differentiation of myotube in vitro.