@article{686b26931ee44963ba7f74146dcec3a7,
title = "Fab-based inhibitors reveal ubiquitin independent functions for HIV Vif neutralization of APOBEC3 restriction factors",
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.",
author = "Binning, {Jennifer M.} and Smith, {Amber M.} and Hultquist, {Judd Franklin} and Craik, {Charles S.} and {Caretta Cartozo}, Nathalie and Campbell, {Melody G.} and Lily Burton and {La Greca}, Florencia and McGregor, {Michael J.} and Ta, {Hai M.} and Koen Bartholomeeusen and Peterlin, {B. Matija} and Krogan, {Nevan J.} and Natalia Sevillano and Yifan Cheng and Gross, {John D.}",
note = "Funding Information: This research was supported by NIH/NIGMS funding for the HIV Accessory & Regulatory Complexes (HARC) Center (P50 GM082250, BMP, CSC, YC, NJK and JDG), NIH/NIAID funding for developing inhibitors of the Vif E3 ligase (R21AI118528, JDG) (NIH funding for the FluOMICs cooperative agreement (U19 AI106754, JFH and NJK), NIH/NIAID funding for the HIV Immune Networks Team (P01 AI090935, NJK), NIH funding for the UCSF-Gladstone Institute of Virology & Immunology Center for AIDS Research (CFAR, P30 AI027763), NIH S10OD020054 (YC), an NIH/NIAID postdoctoral fellowship (F32-AI120867 to JMB), an NIH/GM postdoctoral fellowship (F32-GM123536 to AMS), and amfAR grant 109504-61-RKRL, awarded to JFH using funds raised by generationCURE. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We thank all members of Gross, Krogan, Cheng, and Craik labs for suggestions and technical assistance. The authors also thank David Veesler for providing access to the CryoEM center of the Department of Biochemistry at the University of Washington. Additionally, we would like to thank Hiroshi Matsuo at the University of Minnesota and Alex Bullock at the University of Oxford for kindly providing us with A3F-CTD 11x and SOCS4 expression plasmids, respectively. Publisher Copyright: {\textcopyright} 2018 Binning et al.",
year = "2018",
month = jan,
doi = "10.1371/journal.ppat.1006830",
language = "English (US)",
volume = "14",
journal = "PLoS Pathogens",
issn = "1553-7366",
publisher = "Public Library of Science",
number = "1",
}
