The C-terminus of myogenin, but not MyoD, targets upregulation of MEF2C expression.

The myogenic regulatory family of basic helix-loop-helix transcription factors, including MyoD and myogenin, functions cooperatively with the myocyte-specific enhancer binding factor 2 (MEF2) family during skeletal myogenesis. Previously, using aggregated P19 cells, we have shown that myogenin upregulates MEF2C expression while MyoD does not [Ridgeway et al., J. Biol. Chem. 275 (2000) 41-46]. In order to identify the domain of myogenin responsible for activating MEF2C expression, a series of chimeras of MyoD and myogenin were generated. Only chimeras containing the C-terminal region of myogenin were able to activate MEF2C in aggregated P19 cells, suggesting that the C-terminus of myogenin is responsible for the regulation of specific target genes.