Fig. 5

Epigenetic regulation in differentiating myogenic cells. a In the initial stage of differentiation, PAX7 and MYF5 expression is inhibited via H3K27me3 catalyzed by PRC2 (YY1-EZH2 complex) and additionally, other unknown factors (inhibition of MYF5). Conversely, MYOD gains active transcription marks (H3K4me3, acetylation) through the combined action of TrxG, MEF2, PCAF-p300/CBP, SRF, as well as the SWI/SNF complex. The high level of MYOD contributes to an increase in the production of MYOG and via the action of KDM4A, TrxG, phosphorylated MEF2, UTX, SET7 and also by SWI/SNF complex. Additionally, EZH1 must be present on the MYOG promoter to enable its transcription. The combined action of MYOD and MYOG leads to the expression of genes characteristic for late differentiation, such as MRF4 (b), then levels of MYOD and MYOG decrease in response to the G9a HKMT and the PRC2-YY1 complex, respectively, and due to other unknown factors. c In the terminal differentiation, the level of MRF4 remains high and proteins characteristic for mature skeletal muscle such as MYHC, CKM, and ACNT1 are generated