title: A kinase-independent activity of Cdk9 modulates glucocorticoid receptor-mediated gene induction.
abstract: A gene induction competition assay has recently uncovered new inhibitory activities of two transcriptional cofactors, NELF-A and NELF-B, in glucocorticoid-regulated transactivation. NELF-A and -B are also components of the NELF complex, which participates in RNA polymerase II pausing shortly after the initiation of gene transcription. We therefore asked if cofactors (Cdk9 and ELL) best known to affect paused polymerase could reverse the effects of NELF-A and -B. Unexpectedly, Cdk9 and ELL augmented, rather than prevented, the effects of NELF-A and -B. Furthermore, Cdk9 actions are not blocked either by Ckd9 inhibitors (DRB or flavopiridol) or by two Cdk9 mutants defective in kinase activity. The mode and site of action of NELF-A and -B mutants with an altered NELF domain are similarly affected by wild-type and kinase-dead Cdk9. We conclude that Cdk9 is a new modulator of GR action, that Ckd9 and ELL have novel activities in GR-regulated gene expression, that NELF-A and -B can act separately from the NELF complex, and that Cdk9 possesses activities that are independent of Cdk9 kinase activity. Finally, the competition assay has succeeded in ordering the site of action of several cofactors of GR transactivation. Extension of this methodology should be helpful in determining the site and mode of action of numerous additional cofactors and in reducing unwanted side effects.
authors.affiliation: Steroid Hormones Section, National Institute of Diabetes and Digestive and Kidney Diseases/Laboratory of Endocrinology and Receptor Biology, and ‡Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892, United States.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhu
authors.forename: Xinping
authors.initials: X
authors.lastname: Lu
authors.forename: Madhumita
authors.initials: M
authors.lastname: Pradhan
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Armstrong
authors.forename: Geoffrey B
authors.initials: GB
authors.lastname: Storchan
authors.forename: Carson C
authors.initials: CC
authors.lastname: Chow
authors.forename: S Stoney
authors.initials: SS
authors.lastname: Simons
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D042863:Cyclin-Dependent Kinase 9 / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D009154:Mutation / Q000235:genetics; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology; D015533:Transcriptional Activation / Q000235:genetics*
chemical_list: D011965:Receptors, Glucocorticoid; D014157:Transcription Factors; C118437:negative elongation factor; C467969:CDK9 protein, human; D042863:Cyclin-Dependent Kinase 9