Fig. 8.

Model for p8 function at the myogenin promoter. p8 might act to nucleate a group of chromatin-binding and transcription factors – p68, p300 and MyoD – required for the activation of the myogenin promoter. All three proteins share anti-proliferative and pro-myogenic effects with p8 and are shown to interact, suggesting the possibility that they act as a complex. However, our data do not distinguish between the alternative models shown here: a complex in which p8 co-interacts with all three factors (A), or individual interactions of p68, p300 or MyoD with p8 (B). Because strong expression of p8 marks early-mid G1, this regulatory node might participate in restricting competence for myogenic differentiation to the G1 phase of the cell cycle.