SIRT7-dependent deacetylation of CDK9 activates RNA polymerase II transcription

Blank, Maximilian F.; Chen, Sifan; Poetz, Fabian; Schnölzer, Martina; Voit, Renate; Grummt, Ingrid

CDK9-dependent phosphorylation of the Pol II CTD is required for efficient promoter clearance and transcriptional processivity (34, 35) . Given that SIRT7 counteracts GCN5-directed acetylation of CDK9, we reasoned that deacetylation by SIRT7 should activate CDK9 and increase CTD phosphorylation. To test this, we performed in vitro assays monitoring CDK9-dependent phosphorylation of RPB1, the large subunit of Pol II. Consistent with previous studies (32, 33) , CTD phosphorylation was compromised if CDK9 was hyperacetylated, i.e. if CDK9 was isolated from cells co-expressing GCN5 and treated with the sirtuin inhibitor NAM ( Figure 3F and Supplementary Figures S3E and S3F ), underscoring that acetylation inhibits the kinase activity of CDK9.