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Elife. 2016 Oct 12;5. pii: e15910. doi: 10.7554/eLife.15910.

Insights into HIV-1 proviral transcription from integrative structure and dynamics of the Tat:AFF4:P-TEFb:TAR complex.

Author information

1
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States.
2
California Institute of Quantitative Biosciences, University of California, Berkeley, Berkeley, United States.
3
Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, United States.
4
Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States.
5
California Institute of Quantitative Biosciences, University of California San, Francisco, San Francisco, United States.
6
Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States.
7
Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States.
8
Department of Chemistry, University of California, Berkeley, Berkeley, United States.

Abstract

HIV-1 Tat hijacks the human superelongation complex (SEC) to promote proviral transcription. Here we report the 5.9 Å structure of HIV-1 TAR in complex with HIV-1 Tat and human AFF4, CDK9, and CycT1. The TAR central loop contacts the CycT1 Tat-TAR recognition motif (TRM) and the second Tat Zn2+-binding loop. Hydrogen-deuterium exchange (HDX) shows that AFF4 helix 2 is stabilized in the TAR complex despite not touching the RNA, explaining how it enhances TAR binding to the SEC 50-fold. RNA SHAPE and SAXS data were used to help model the extended (Tat Arginine-Rich Motif) ARM, which enters the TAR major groove between the bulge and the central loop. The structure and functional assays collectively support an integrative structure and a bipartite binding model, wherein the TAR central loop engages the CycT1 TRM and compact core of Tat, while the TAR major groove interacts with the extended Tat ARM.

KEYWORDS:

HDX; SAXS; SHAPE; X-ray crystallography; biochemistry; biophysics; integrative modeling; structural biology; virus

PMID:
27731797
PMCID:
PMC5072841
DOI:
10.7554/eLife.15910
[Indexed for MEDLINE]
Free PMC Article

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