期刊
MOLECULAR CELL
卷 38, 期 3, 页码 428-438出版社
CELL PRESS
DOI: 10.1016/j.molcel.2010.04.013
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资金
- NIAID NIH HHS [R01AI41757-11S1, R01AI41757-11, R01 AI041757] Funding Source: Medline
- NIGMS NIH HHS [P50 GM082250, P50 GM82250, P50 GM082250-03] Funding Source: Medline
Recruitment of the P-TEFb kinase by HIV-1 Tat to the viral promoter triggers the phosphorylation and escape of RNA polymerase II from promoter-proximal pausing. It is unclear, however, if Tat recruits additional host factors that further stimulate HIV-1 transcription. Using a sequential affinity-purification scheme, we have identified human transcription factors/coactivators AFF4, ENL, AF9, and elongation factor ELL2 as components of the Tat-P-TEFb complex. Through the bridging functions of Tat and AFF4, P-TEFb and ELL2 combine to form a bifunctional elongation complex that greatly activates HIV-1 transcription. Without Tat, AFF4 can mediate the ELL2-PTEFb interaction, albeit inefficiently. Tat overcomes this limitation by bringing more ELL2 to P-TEFb and stabilizing ELL2 in a process that requires active P-TEFb. The ability of Tat to enable two different classes of elongation factors to cooperate and coordinate their actions on the same polymerase enzyme explains why Tat is such a powerful activator of HIV-1 transcription.
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