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BioMed Research International
Volume 2014, Article ID 232870, 11 pages
http://dx.doi.org/10.1155/2014/232870
Review Article

Brd4 and HEXIM1: Multiple Roles in P-TEFb Regulation and Cancer

1State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian 361005, China
2Department of Orthopaedic Surgery, Lawrence J. Ellison Musculoskeletal Research Center, University of California at Davis Medical Center, Sacramento, CA 95817, USA
3Expression Engineering Group, Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), 20 Biopolis Way, No. 06-01, Singapore 138668
4Department of Microbiology, National University of Singapore, Block MD4, 5 Science Drive 2, Singapore 117597

Received 6 November 2013; Accepted 19 December 2013; Published 29 January 2014

Academic Editor: Kaei Nasu

Copyright © 2014 Ruichuan Chen 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.

Abstract

Bromodomain-containing protein 4 (Brd4) and hexamethylene bisacetamide (HMBA) inducible protein 1 (HEXIM1) are two opposing regulators of the positive transcription elongation factor b (P-TEFb), which is the master modulator of RNA polymerase II during transcriptional elongation. While Brd4 recruits P-TEFb to promoter-proximal chromatins to activate transcription, HEXIM1 sequesters P-TEFb into an inactive complex containing the 7SK small nuclear RNA. Besides regulating P-TEFb’s transcriptional activity, recent evidence demonstrates that both Brd4 and HEXIM1 also play novel roles in cell cycle progression and tumorigenesis. Here we will discuss the current knowledge on Brd4 and HEXIM1 and their implication as novel therapeutic options against cancer.