<scp>MOF</scp>‐mediated acetylation of <scp>CDK</scp>9 promotes global transcription by modulating P‐<scp>TEF</scp>b complex formation

Cyclin‐dependent kinase 9 (CDK9), a catalytic subunit of the positive transcription elongation factor b (P‐TEFb) complex, is a global transcriptional elongation factor associated with cell proliferation. CDK9 activity is regulated by certain histone acetyltransferases, such as p300, GCN5 and P/CAF. However, the impact of males absent on the first (MOF) (also known as KAT8 or MYST1) on CDK9 activity has not been reported. Therefore, the present study aimed to elucidate the regulatory role of MOF on CDK9. We present evidence from systematic biochemical assays and molecular biology approaches arguing that MOF interacts with and acetylates CDK9 at the lysine 35 (i.e. K35) site, and that this acetyl‐group can be removed by histone deacetylase HDAC1. Notably, MOF‐mediated acetylation of CDK9 at K35 promotes the formation of the P‐TEFb complex through stabilizing CDK9 protein and enhancing its association with cyclin T1, which further increases RNA polymerase II serine 2 residues levels and global transcription. Our study reveals for the first time that MOF promotes global transcription by acetylating CDK9, providing a new strategy for exploring the comprehensive mechanism of the MOF–CDK9 axis in cellular processes.