Elucidating the Mechanism by which Compensatory Mutations Rescue an HIV-1 Matrix Mutant Defective for Gag Membrane Targeting and Envelope Glycoprotein Incorporation

Tedbury, Philip R.; Mercredi, Peter Y.; Gaines, Christy; Summers, Michael F.; Freed, Eric O.

doi:10.1016/j.jmb.2015.01.018

Cited by 27 publications

(53 citation statements)

References 48 publications

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“…These findings implicate this central aperture as the site of Env incorporation in the particle. This idea is further supported by the observation that, in cell lines permissive for packaging of CT-truncated Env, removal of the CT relieves the inhibition of Env incorporation imposed by the MA mutations (22,25,28). The ability to rescue Env incorporation by removing the CT suggests that steric hindrance of Env incorporation may be a key mechanism for the loss of Env incorporation imposed by mutations in MA.…”

Section: Significancementioning

confidence: 91%

Biochemical evidence of a role for matrix trimerization in HIV-1 envelope glycoprotein incorporation

Tedbury

Novikova

Ablan

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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122

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The matrix (MA) domain of HIV Gag has important functions in directing the trafficking of Gag to sites of assembly and mediating the incorporation of the envelope glycoprotein (Env) into assembling particles. HIV-1 MA has been shown to form trimers in vitro; however, neither the presence nor the role of MA trimers has been documented in HIV-1 virions. We developed a cross-linking strategy to reveal MA trimers in virions of replication-competent HIV-1. By mutagenesis of trimer interface residues, we demonstrated a correlation between loss of MA trimerization and loss of Env incorporation. Additionally, we found that truncating the long cytoplasmic tail of Env restores incorporation of Env into MA trimer-defective particles, thus rescuing infectivity. We therefore propose a model whereby MA trimerization is required to form a lattice capable of accommodating the long cytoplasmic tail of HIV-1 Env; in the absence of MA trimerization, Env is sterically excluded from the assembling particle. These findings establish MA trimerization as an obligatory step in the assembly of infectious HIV-1 virions. As such, the MA trimer interface may represent a novel drug target for the development of antiretrovirals.HIV | retrovirus | matrix | envelope | trimerization

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Section: Significancementioning

confidence: 91%

Biochemical evidence of a role for matrix trimerization in HIV-1 envelope glycoprotein incorporation

Tedbury

Novikova

Ablan

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

122

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“…The above-described results suggest that ⌬CT Env proteins assemble passively into HIV-1 virions, whereas WT Env proteins require a direct or indirect interaction with MA for virion incorporation (17,18,(22)(23)(24)(25). Because of the unusual length of the HIV-1 Env CT, one can speculate that WT Env trimers are hindered from assembling into lattices organized by PrGag proteins …”

Section: The Hiv-1 Env Proteins Assemble As Trimers and Incorporatiomentioning

confidence: 99%

“…The same is not true for the WT HIV-1 Env protein (17,18). However, HIV-1 Env proteins that carry deletions of the long Env cytoplasmic tail (CT) can be assembled efficiently into either WT or ⌬MA HIV-1 particles (18), at least in cell types that permit the efficient cell surface localization of ⌬CT Env proteins (32, 33).The above-described results suggest that ⌬CT Env proteins assemble passively into HIV-1 virions, whereas WT Env proteins require a direct or indirect interaction with MA for virion incorporation (17,18,(22)(23)(24)(25). Because of the unusual length of the HIV-1 Env CT, one can speculate that WT Env trimers are hindered from assembling into lattices organized by PrGag proteins …”

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confidence: 99%

Trimer Enhancement Mutation Effects on HIV-1 Matrix Protein Binding Activities

Alfadhli

Mack

Ritchie

et al. 2016

J Virol

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The HIV-1 matrix (MA) protein is the amino-terminal domain of the HIV-1 precursor Gag (Pr55Gag) protein. MA binds to membranes and RNAs, helps transport Pr55Gag proteins to virus assembly sites at the plasma membranes of infected cells, and facilitates the incorporation of HIV-1 envelope (Env) proteins into virions by virtue of an interaction with the Env protein cytoplasmic tails (CTs). MA has been shown to crystallize as a trimer and to organize on membranes in hexamer lattices. MA mutations that localize to residues near the ends of trimer spokes have been observed to impair Env protein assembly into virus particles, and several of these are suppressed by the 62QR mutation at the hubs of trimer interfaces. We have examined the binding activities of wild-type (WT) MA and 62QR MA variants and found that the 62QR mutation stabilized MA trimers but did not alter the way MA proteins organized on membranes. Relative to WT MA, the 62QR protein showed small effects on membrane and RNA binding. However, 62QR proteins bound significantly better to Env CTs than their WT counterparts, and CT binding efficiencies correlated with trimerization efficiencies. Our data suggest a model in which multivalent binding of trimeric HIV-1 Env proteins to MA trimers contributes to the process of Env virion incorporation. T he matrix (MA) domain of the human immunodeficiency type 1 (HIV-1) precursor Gag (Pr55Gag) protein serves several assembly-related functions. One role is to direct Pr55Gag proteins to assembly sites at cell plasma membranes (PMs) that are enriched for phosphatidylinositol-4,5-bisphosphate (PI[4,5]P2) and cholesterol (1-8). This function is accomplished in part by virtue of an amino-terminal myristate moiety and, in part, through direct binding to PI(4,5)P2 (1). Evidence indicates that the PI(4,5)P2-binding site on MA overlaps a binding site for RNA, which suggests a chaperone model in which MA-RNA binding protects the MA domain of Pr55Gag from associating with inappropriate intracellular membranes prior to delivery to the PI(4,5)P2-rich PM assembly sites (9-16). In some experimental systems, it has been shown that Pr55Gag proteins with MA deletions (⌬MA) or swaps of MA with other membrane binding domains are capable of directing the assembly of conditionally infectious viruses, but in these cases, assembly and replication efficiencies have tended to be compromised (17)(18)(19)(20)(21). IMPORTANCE The HIV-1 Env proteins assemble as trimers, and incorporation of the proteins into virus particles requires an interaction of EnvA second role of HIV-1 MA is to facilitate the incorporation of envelope (Env) proteins into virions (22-25). How MA accomplishes this is complicated. One confounding issue is that some cell surface proteins can be assembled into HIV-1 particles in what appears to be a passive fashion (26). Indeed, this is how glycoproteins from other viruses can pseudotype with the cores of HIV-1 (17, 27-31). Presumably, PM proteins that localize to HIV-1 assembly sites can be incorporated into viruses as...

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“…Regarding the interaction domains, data from mutagenesis analyses suggest that amino acid substitutions (e.g., E16K, K29E, K31E, and E99V) in matrix Gag can impair Env packaging (74,75,292,298). Substitutions at serine positions (S9, S67, S72, and S77) in HIV-1 matrix Gag dramatically reduce the phosphorylation of matrix Gag and inhibit the binding of matrix Gag to lipid rafts, thereby causing an impairment of Env packaging (299).…”

Section: Lymphocytes (292) (Iii) Given That Gag and Env Proteins Arementioning

confidence: 99%

HIV Genome-Wide Protein Associations: a Review of 30 Years of Research

Clercq

2016

Microbiol Mol Biol Rev

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SUMMARYThe HIV genome encodes a small number of viral proteins (i.e., 16), invariably establishing cooperative associations among HIV proteins and between HIV and host proteins, to invade host cells and hijack their internal machineries. As a known example, the HIV envelope glycoprotein GP120 is closely associated with GP41 for viral entry. From a genome-wide perspective, a hypothesis can be worked out to determine whether 16 HIV proteins could develop 120 possible pairwise associations either by physical interactions or by functional associations mediated via HIV or host molecules. Here, we present the first systematic review of experimental evidence on HIV genome-wide protein associations using a large body of publications accumulated over the past 3 decades. Of 120 possible pairwise associations between 16 HIV proteins, at least 34 physical interactions and 17 functional associations have been identified. To achieve efficient viral replication and infection, HIV protein associations play essential roles (e.g., cleavage, inhibition, and activation) during the HIV life cycle. In either a dispensable or an indispensable manner, each HIV protein collaborates with another viral protein to accomplish specific activities that precisely take place at the proper stages of the HIV life cycle. In addition, HIV genome-wide protein associations have an impact on anti-HIV inhibitors due to the extensive cross talk between drug-inhibited proteins and other HIV proteins. Overall, this study presents for the first time a comprehensive overview of HIV genome-wide protein associations, highlighting meticulous collaborations between all viral proteins during the HIV life cycle.

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Elucidating the Mechanism by which Compensatory Mutations Rescue an HIV-1 Matrix Mutant Defective for Gag Membrane Targeting and Envelope Glycoprotein Incorporation

Cited by 27 publications

References 48 publications

Biochemical evidence of a role for matrix trimerization in HIV-1 envelope glycoprotein incorporation

Biochemical evidence of a role for matrix trimerization in HIV-1 envelope glycoprotein incorporation

Trimer Enhancement Mutation Effects on HIV-1 Matrix Protein Binding Activities

HIV Genome-Wide Protein Associations: a Review of 30 Years of Research

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