Format

Send to

Choose Destination
PLoS Pathog. 2018 Jan 5;14(1):e1006830. doi: 10.1371/journal.ppat.1006830. eCollection 2018 Jan.

Fab-based inhibitors reveal ubiquitin independent functions for HIV Vif neutralization of APOBEC3 restriction factors.

Author information

1
Department of Pharmaceutical Chemistry, University of California, San Francisco, California, United States of America.
2
Keck Advanced Microscopy Laboratory and Department of Biochemistry and Biophysics, University of California, San Francisco, California, United States of America.
3
Howard Hughes Medical Institute, University of California, San Francisco, California, United States of America.
4
J. David Gladstone Institutes, San Francisco, California, United States of America.
5
Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California, United States of America.
6
California Institute for Quantitative Biosciences, QB3, University of California, San Francisco, San Francisco, California, United States of America.
7
Department of Medicine, University of California, San Francisco, California, United States of America.
8
Department of Microbiology, University of California, San Francisco, California, United States of America.
9
Department of Immunology, University of California, San Francisco, California, United States of America.

Abstract

The lentiviral protein Viral Infectivity Factor (Vif) counteracts the antiviral effects of host APOBEC3 (A3) proteins and contributes to persistent HIV infection. Vif targets A3 restriction factors for ubiquitination and proteasomal degradation by recruiting them to a multi-protein ubiquitin E3 ligase complex. Here, we describe a degradation-independent mechanism of Vif-mediated antagonism that was revealed through detailed structure-function studies of antibody antigen-binding fragments (Fabs) to the Vif complex. Two Fabs were found to inhibit Vif-mediated A3 neutralization through distinct mechanisms: shielding A3 from ubiquitin transfer and blocking Vif E3 assembly. Combined biochemical, cell biological and structural studies reveal that disruption of Vif E3 assembly inhibited A3 ubiquitination but was not sufficient to restore its packaging into viral particles and antiviral activity. These observations establish that Vif can neutralize A3 family members in a degradation-independent manner. Additionally, this work highlights the potential of Fabs as functional probes, and illuminates how Vif uses a multi-pronged approach involving both degradation dependent and independent mechanisms to suppress A3 innate immunity.

PMID:
29304101
PMCID:
PMC5773222
DOI:
10.1371/journal.ppat.1006830
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Public Library of Science Icon for PubMed Central
Loading ...
Support Center