AFF4 binding to Tat-P-TEFb indirectly stimulates TAR recognition of super elongation complexes at the HIV promoter

  1. Ursula Schulze-Gahmen  Is a corresponding author
  2. Huasong Lu
  3. Qiang Zhou
  4. Tom Alber
  1. University of California, Berkeley, United States

Abstract

Superelongation complexes (SECs) are essential for transcription elongation of many human genes, including the integrated HIV-1 genome. At the HIV-1 promoter, the viral Tat protein binds simultaneously to the nascent TAR RNA and the CycT1 subunit of the P-TEFb kinase in a SEC. To understand the preferential recruitment of SECs by Tat and TAR, we determined the crystal structure of a quaternary complex containing Tat, P-TEFb, and the SEC scaffold, AFF4. Tat and AFF4 fold on the surface of CycT1 and interact directly. Interface mutations in the AFF4 homolog AFF1 reduced Tat-AFF1 affinity in vivo and Tat-dependent transcription from the HIV promoter. AFF4 binding in the presence of Tat partially orders the CycT1 Tat-TAR recognition motif and increases the affinity of Tat-P-TEFb for TAR 30-fold. These studies indicate that AFF4 acts as a two-step filter to increase the selectivity of Tat and TAR for SECs over P-TEFb alone.

Article and author information

Author details

  1. Ursula Schulze-Gahmen

    University of California, Berkeley, Berkeley, United States
    For correspondence
    uschulze-gahmen@lbl.gov
    Competing interests
    The authors declare that no competing interests exist.
  2. Huasong Lu

    University of California, Berkeley, Berkeley, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Qiang Zhou

    University of California, Berkeley, Berkeley, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Tom Alber

    University of California, Berkeley, Berkeley, United States
    Competing interests
    The authors declare that no competing interests exist.

Reviewing Editor

  1. Wesley Sundquist, University of Utah, United States

Publication history

  1. Received: January 22, 2014
  2. Accepted: April 4, 2014
  3. Accepted Manuscript published: April 24, 2014 (version 1)
  4. Version of Record published: May 8, 2014 (version 2)

Copyright

© 2014, Schulze-Gahmen et al.

This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.

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  1. Ursula Schulze-Gahmen
  2. Huasong Lu
  3. Qiang Zhou
  4. Tom Alber
(2014)
AFF4 binding to Tat-P-TEFb indirectly stimulates TAR recognition of super elongation complexes at the HIV promoter
eLife 3:e02375.
https://doi.org/10.7554/eLife.02375

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