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BioMed Research International
Volume 2014, Article ID 964964, 8 pages
Review Article

Regulation of CDK9 Activity by Phosphorylation and Dephosphorylation

1Center for Sickle Cell Disease, Department of Medicine, Howard University, 520 W Street, N.W. Washington, DC 20059, USA
2Division of Molecular and Radiation Biophysics, Petersburg Nuclear Physics Institute, Gatchina 188350, Russia
3Department of Biophysics, St. Petersburg State Polytechnical University, Polytechnicheskaya Street 29, St. Petersburg 195251, Russia

Received 20 October 2013; Accepted 11 December 2013; Published 12 January 2014

Academic Editor: Sheng-Hao Chao

Copyright © 2014 Sergei Nekhai et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


HIV-1 transcription is regulated by CDK9/cyclin T1, which, unlike a typical cell cycle-dependent kinase, is regulated by associating with 7SK small nuclear ribonuclear protein complex (snRNP). While the protein components of this complex are well studied, the mechanism of the complex formation is still not fully understood. The association of CDK9/cyclin T1 with 7SK snRNP is, in part, regulated by a reversible CDK9 phosphorylation. Here, we present a comprehensive review of the kinases and phosphatases involved in CDK9 phosphorylation and discuss their role in regulation of HIV-1 replication and potential for being targeted for drug development. We propose a novel pathway of HIV-1 transcription regulation via CDK9 Ser-90 phosphorylation by CDK2 and CDK9 Ser-175 dephosphorylation by protein phosphatase-1.