CDK9 and Miyoshi myopathy: Collectively, these and the preceding findings indicate that MM cells are characterized by pronounced constitutive expression and activation of the transcriptional regulatory apparatus e.g., expression of cyclin T1, expression and phosphorylation of CDK9, association of CDK9/cyclin T1/RNAPII, and S2 phosphorylation/activation of the carboxy-terminal domain of RNAPII.