The HIV-1 Tat protein recruits a ubiquitin ligase to reorganize the 7SK snRNP for transcriptional activation

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Abstract

The HIV-1 Tat protein hijacks P-TEFb kinase to activate paused RNA polymerase II (RNAP II) at the viral promoter. Tat binds additional host factors, but it is unclear how they regulate RNAP II elongation. Here we identify the cytoplasmic ubiquitin ligase UBE2O as critical for Tat transcriptional activity. Tat hijacks UBE2O to ubiquitinate the P-TEFb kinase inhibitor HEXIM1 of the 7SK snRNP, a fraction of which also resides in the cytoplasm bound to P-TEFb. HEXIM1 ubiquitination sequesters it in the cytoplasm and releases P-TEFb from the inhibitory 7SK complex. Free P-TEFb then becomes enriched in chromatin, a process that is also stimulated by treating cells with a CDK9 inhibitor. Finally, we demonstrate that UBE2O is critical for P-TEFb recruitment to the HIV-1 promoter. Together, the data support a unique model of elongation control where non-degradative ubiquitination of nuclear and cytoplasmic 7SK snRNP pools increases P-TEFb levels for transcriptional activation.

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All data generated or analysed during this study are included in the manuscript and supporting files.

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Tyler B Faust

Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States

Competing interests
The authors declare that no competing interests exist.
Yang Li

Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States

Competing interests
The authors declare that no competing interests exist.
Curtis W Bacon

Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, United States

Competing interests
The authors declare that no competing interests exist.
Gwendolyn M Jang

Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States

Competing interests
The authors declare that no competing interests exist.
Amit Weiss

Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States

Competing interests
The authors declare that no competing interests exist.
Bhargavi Jayaraman

Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States

Competing interests
The authors declare that no competing interests exist.
Billy W Newton

Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States

Competing interests
The authors declare that no competing interests exist.
Nevan J Krogan

Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, United States

Competing interests
The authors declare that no competing interests exist.
Iván D'Orso

Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, United States

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The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-1409-2351
Alan D Frankel

Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States

For correspondence
frankel@cgl.ucsf.edu

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-2525-9508

Funding

National Institute of General Medical Sciences (P50GM082250)

Nevan J Krogan
Alan D Frankel

National Institute of Allergy and Infectious Diseases (RO1AI114362)

Iván D'Orso

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

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