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Recruitment of P-TEFb for stimulation of transcriptional elongation by the bromodomain protein Brd4.

The cyclinT1/Cdk9 heterodimer that constitutes core P-TEFb is generally presumed to be the transcriptionally active form for stimulating RNA polymerase II elongation. About half of cellular P-TEFb also exists in an inactive complex with the 7SK snRNA and the HEXIM1 protein. Here, we show that the remaining half associates with the bromodomain protein Brd4. In stress-induced cells, the 7SK/HEXIM1-bound P-TEFb is quantitatively converted into the Brd4-associated form. The association with Brd4 is necessary to form the transcriptionally active P-TEFb, recruits P-TEFb to a promoter, and enables P-TEFb to contact the Mediator complex, a potential target for the Brd4-mediated recruitment. Although generally required for transcription, the P-TEFb-recruitment function of Brd4 can be substituted by that of HIV-1 Tat, which recruits P-TEFb directly for activated HIV-1 transcription. Brd4, HEXIM1, and 7SK are all implicated in regulating cell growth, which may result from their dynamic control of the general transcription factor P-TEFb.

Pubmed ID: 16109377


  • Yang Z
  • Yik JH
  • Chen R
  • He N
  • Jang MK
  • Ozato K
  • Zhou Q


Molecular cell

Publication Data

August 19, 2005

Associated Grants

  • Agency: NIAID NIH HHS, Id: AI058400
  • Agency: NIAID NIH HHS, Id: AI41757

Mesh Terms

  • Base Sequence
  • Cyclin-Dependent Kinase 9
  • Gene Products, tat
  • HIV-1
  • HeLa Cells
  • Humans
  • Molecular Sequence Data
  • Nuclear Proteins
  • Oncogene Proteins, Fusion
  • Positive Transcriptional Elongation Factor B
  • RNA Polymerase II
  • Transcription Factors
  • Transcription, Genetic
  • tat Gene Products, Human Immunodeficiency Virus