MYOD1, also named as BHLHC1 or MYF3, is a 320 amino acid protein, which promotes the transcriptional activity of MYOD1 through its CDK9-mediated phosphorylation. This phosphorylation promotes its function in muscle differentiation. MYOD1 acts as a transcriptional activator that promotes transcription of muscle-specific target genes and plays a role in muscle differentiation. MYOD1 together with MYF5 and MYOG, co-occupies muscle-specific gene promoter core region during myogenesis. Induces fibroblasts to differentiate into myoblasts. he calcualted molecular weight of MYOD1 is 34 kDa, but modified MYOD1 is about 45 kDa.