Project description:MyoD and NeuroD2 are master regulators of myogenesis and neurogenesis and bind to a "shared" E-box sequence (CAGCTG) and a "private" sequence (CAGGTG or CAGATG, respectively). To determine whether private-site recognition is sufficient to confer lineage-specification, we generated a MyoD-mutant with the DNA binding specificity of NeuroD2. Our results demonstrate that redirecting MyoD binding from MyoD-private sites to NeuroD2-private sites, despite preserved binding to the MyoD/NeuroD2-shared sites, is sufficient to change MyoD from a master regulator of myogenesis to a master regulator of neurogenesis. ChIP-seq profiling of MyoD, NeuroD2 and chimera mutants in mouse P19 cells transfected with these genes. The chimeric mutants are MyoD with the bHLH domain replaced with the NeuroD2 bHLH domain.
Project description:The transcriptional activator MyoD serves as a master controller of myogenesis. Often in partnership with Mef2, MyoD binds to the promoters of hundreds of muscle genes in proliferating myoblasts, yet activates these targets only upon receiving cues that launch differentiation. What regulates this off/on switch of MyoD function has been incompletely understood, although known to reflect the action of chromatin modifiers. Here, we identify KAP1/TRIM28 as a key regulator of MyoD function. In myoblasts, KAP1 is present with MyoD and Mef2 at many muscle genes, where it acts as a scaffold to recruit not only co-activators such as p300 and LSD1, but also co-repressors such as G9a and HDAC1, with promoter silencing as net outcome. Upon differentiation, MSK1-mediated phosphorylation of KAP1 releases the co-repressors from the scaffold, unleashing transcriptional activation by MyoD/Mef2 and their positive cofactors. Thus, our results reveal KAP1 as a previously unappreciated interpreter of cell signaling, which modulates the ability of MyoD to drive myogenesis. Kap1 and H3K9me3 ChIPseq in proliferating C2C12 cells