Figure 1.

Transcriptional and epigenetic regulators of satellite cell quiescence, proliferation and differentiation. (Top) During homeostasis, quiescent satellite cells express Pax7. Pax7 promoter is active, holding active chromatin marks, and being transcriptionally regulated by the Notch signaling pathway with the Notch intracellular domain (NICD) interacting with the effector protein recombining binding protein-Jκ (RBPJκ) (Wen et al., 2012), and although not demonstrated, probably populated by active chromatin remodelers and HATs. (Middle) In quiescent and proliferating satellite cells, muscle-specific gene promoters are repressed. MyoD is associated with several repressors (like Id) and Sir2 in a complex that also contains pCAF. MyoD, YY1, and MEF2 factors recruit the PRC2 complex, Suv39H1, and class I/II HDACs. DNMTs associate and methylate the DNA, and chromatin is populated with repressive histone marks. (Bottom) Upon differentiation cues, transcriptionally active muscle-specific promoters contain active phosphorylated MyoD/E heterodimers, phosphorylated MEF2 dimers and SRF transcription factors. In collaboration with arginine methyltransferases Prmt4/5, the SWI/SNF remodeling complex, HATs and Thritorax complexes will be recruited. DNA will be demethylated, and chromatin acetylated and populated with active histone marks.