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Title: Identification of a Structural Element in HIV-1 Gag Required for Virus Particle Assembly and Maturation

Abstract

ABSTRACT Late in the HIV-1 replication cycle, the viral structural protein Gag is targeted to virus assembly sites at the plasma membrane of infected cells. The capsid (CA) domain of Gag plays a critical role in the formation of the hexameric Gag lattice in the immature virion, and, during particle release, CA is cleaved from the Gag precursor by the viral protease and forms the conical core of the mature virion. A highly conserved Pro-Pro-Ile-Pro (PPIP) motif (CA residues 122 to 125) [PPIP(122–125)] in a loop connecting CA helices 6 and 7 resides at a 3-fold axis formed by neighboring hexamers in the immature Gag lattice. In this study, we characterized the role of this PPIP(122–125) loop in HIV-1 assembly and maturation. While mutations P123A and P125A were relatively well tolerated, mutation of P122 and I124 significantly impaired virus release, caused Gag processing defects, and abolished infectivity. X-ray crystallography indicated that the P122A and I124A mutations induce subtle changes in the structure of the mature CA lattice which were permissive forin vitroassembly of CA tubes. Transmission electron microscopy and cryo-electron tomography demonstrated that the P122A and I124A mutations induce severe structural defects in the immature Gag lattice and abrogate conicalmore » core formation. Propagation of the P122A and I124A mutants in T-cell lines led to the selection of compensatory mutations within CA. Our findings demonstrate that the CA PPIP(122–125) loop comprises a structural element critical for the formation of the immature Gag lattice. IMPORTANCECapsid (CA) plays multiple roles in the HIV-1 replication cycle. CA-CA domain interactions are responsible for multimerization of the Gag polyprotein at virus assembly sites, and in the mature virion, CA monomers assemble into a conical core that encapsidates the viral RNA genome. Multiple CA regions that contribute to the assembly and release of HIV-1 particles have been mapped and investigated. Here, we identified and characterized a Pro-rich loop in CA that is important for the formation of the immature Gag lattice. Changes in this region disrupt viral production and abrogate the formation of infectious, mature virions. Propagation of the mutants in culture led to the selection of second-site compensatory mutations within CA. These results expand our knowledge of the assembly and maturation steps in the viral replication cycle and may be relevant for development of antiviral drugs targeting CA.« less

Authors:
; ; ORCiD logo; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
National Institutes of Health (NIH)
OSTI Identifier:
1502210
Resource Type:
Journal Article
Journal Name:
mBio (Online)
Additional Journal Information:
Journal Volume: 9; Journal Issue: 5; Journal ID: ISSN 2150-7511
Publisher:
American Society for Microbiology
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Novikova, Mariia, Adams, Lucas J., Fontana, Juan, Gres, Anna T., Balasubramaniam, Muthukumar, Winkler, Dennis C., Kudchodkar, Sagar B., Soheilian, Ferri, Sarafianos, Stefan G., Steven, Alasdair C., Freed, Eric O., and Goff, Stephen P. Identification of a Structural Element in HIV-1 Gag Required for Virus Particle Assembly and Maturation. United States: N. p., 2018. Web. doi:10.1128/mBio.01567-18.
Novikova, Mariia, Adams, Lucas J., Fontana, Juan, Gres, Anna T., Balasubramaniam, Muthukumar, Winkler, Dennis C., Kudchodkar, Sagar B., Soheilian, Ferri, Sarafianos, Stefan G., Steven, Alasdair C., Freed, Eric O., & Goff, Stephen P. Identification of a Structural Element in HIV-1 Gag Required for Virus Particle Assembly and Maturation. United States. doi:10.1128/mBio.01567-18.
Novikova, Mariia, Adams, Lucas J., Fontana, Juan, Gres, Anna T., Balasubramaniam, Muthukumar, Winkler, Dennis C., Kudchodkar, Sagar B., Soheilian, Ferri, Sarafianos, Stefan G., Steven, Alasdair C., Freed, Eric O., and Goff, Stephen P. Tue . "Identification of a Structural Element in HIV-1 Gag Required for Virus Particle Assembly and Maturation". United States. doi:10.1128/mBio.01567-18.
@article{osti_1502210,
title = {Identification of a Structural Element in HIV-1 Gag Required for Virus Particle Assembly and Maturation},
author = {Novikova, Mariia and Adams, Lucas J. and Fontana, Juan and Gres, Anna T. and Balasubramaniam, Muthukumar and Winkler, Dennis C. and Kudchodkar, Sagar B. and Soheilian, Ferri and Sarafianos, Stefan G. and Steven, Alasdair C. and Freed, Eric O. and Goff, Stephen P.},
abstractNote = {ABSTRACT Late in the HIV-1 replication cycle, the viral structural protein Gag is targeted to virus assembly sites at the plasma membrane of infected cells. The capsid (CA) domain of Gag plays a critical role in the formation of the hexameric Gag lattice in the immature virion, and, during particle release, CA is cleaved from the Gag precursor by the viral protease and forms the conical core of the mature virion. A highly conserved Pro-Pro-Ile-Pro (PPIP) motif (CA residues 122 to 125) [PPIP(122–125)] in a loop connecting CA helices 6 and 7 resides at a 3-fold axis formed by neighboring hexamers in the immature Gag lattice. In this study, we characterized the role of this PPIP(122–125) loop in HIV-1 assembly and maturation. While mutations P123A and P125A were relatively well tolerated, mutation of P122 and I124 significantly impaired virus release, caused Gag processing defects, and abolished infectivity. X-ray crystallography indicated that the P122A and I124A mutations induce subtle changes in the structure of the mature CA lattice which were permissive forin vitroassembly of CA tubes. Transmission electron microscopy and cryo-electron tomography demonstrated that the P122A and I124A mutations induce severe structural defects in the immature Gag lattice and abrogate conical core formation. Propagation of the P122A and I124A mutants in T-cell lines led to the selection of compensatory mutations within CA. Our findings demonstrate that the CA PPIP(122–125) loop comprises a structural element critical for the formation of the immature Gag lattice. IMPORTANCECapsid (CA) plays multiple roles in the HIV-1 replication cycle. CA-CA domain interactions are responsible for multimerization of the Gag polyprotein at virus assembly sites, and in the mature virion, CA monomers assemble into a conical core that encapsidates the viral RNA genome. Multiple CA regions that contribute to the assembly and release of HIV-1 particles have been mapped and investigated. Here, we identified and characterized a Pro-rich loop in CA that is important for the formation of the immature Gag lattice. Changes in this region disrupt viral production and abrogate the formation of infectious, mature virions. Propagation of the mutants in culture led to the selection of second-site compensatory mutations within CA. These results expand our knowledge of the assembly and maturation steps in the viral replication cycle and may be relevant for development of antiviral drugs targeting CA.},
doi = {10.1128/mBio.01567-18},
journal = {mBio (Online)},
issn = {2150-7511},
number = 5,
volume = 9,
place = {United States},
year = {2018},
month = {10}
}