Regulation of P-TEFb elongation complex activity by CDK9 acetylation.
P-TEFb, comprised of CDK9 and a cyclin T subunit, is a global transcriptional elongation factor important for most RNA polymerase II (pol II) transcription. P-TEFb facilitates transcription elongation in part by phosphorylating Ser2 of the heptapeptide repeat of the carboxy-terminal domain (CTD) of the largest subunit of pol II. Previous studies have shown that P-TEFb is subjected to negative regulation by forming an inactive complex with 7SK small RNA and HEXIM1. In an effort to investigate the molecular mechanism by which corepressor N-CoR mediates transcription repression, we identified HEXIM1 as an N-CoR-interacting protein. This finding led us to test whether the P-TEFb complex is regulated by acetylation. We demonstrate that CDK9 is an acetylated protein in cells and can be acetylated by p300 in vitro. Through both in vitro and in vivo assays, we identified lysine 44 of CDK9 as a major acetylation site. We present evidence that CDK9 is regulated by N-CoR and its associated HDAC3 and that acetylation of CDK9 affects its ability to phosphorylate the CTD of pol II. These results suggest that acetylation of CDK9 is an important posttranslational modification that is involved in regulating P-TEFb transcriptional elongation function.
Fu
Junjiang
J
Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
Yoon
Ho-Geun
HG
Qin
Jun
J
Wong
Jiemin
J
D000107:Acetylation; D000595:Amino Acid Sequence; D042863:Cyclin-Dependent Kinase 9 / Q000737:chemistry / Q000378:metabolism*; D016325:HIV Long Terminal Repeat / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008239:Lysine / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism; D056971:Nuclear Receptor Co-Repressor 1; D042925:Positive Transcriptional Elongation Factor B / Q000378:metabolism*; D011485:Protein Binding; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism; D014157:Transcription Factors; D014158:Transcription, Genetic
C476123:HEXIM1 protein, human; C539127:NCOR1 protein, human; D009687:Nuclear Proteins; D056971:Nuclear Receptor Co-Repressor 1; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D042925:Positive Transcriptional Elongation Factor B; D042863:Cyclin-Dependent Kinase 9; D008239:Lysine