N factor in 2004 [1] and acts within the post-entry, pre-integration window [2,3]. The
N factor in 2004 [1] and acts within the post-entry, pre-integration window [2,3]. The viral molecular target of TRIM5 is the correctly matured N-terminal domain of capsid (CA) proteins forming the outer surface of the retroviral core [2,4-8]. A direct interaction between the two proteins, each present as high molecular weight multimers, occurs shortly after entry and is required for downstream inhibition of viral replication [8-12]. The mechanism of TRIM5-mediated restriction can be broken down to discrete events, some of them inter-dependent: (i) virus entrapment into TRIM5 cytoplasmic bodies [13], (ii) decreased stability of the virus core [8,14-16], (iii) targeting to a proteasome-dependent degradation pathway [17-20], and (iv) inhibition of nuclear transport [17,21,22]. CypA, a host peptidyl-prolyl cis/trans isomerase that is ubiquitously expressed in tissues, is known to play roles in both HIV-1 infection of human cells and in HIV-1 restriction by TRIM5 in monkey cells. In dividing permissive human cells, CypA enhances HIV-1 infectivity by regulating the disassembly of its core [23-25] independently of TRIM5 [26,27]. On the other hand, restriction of HIV-1 by simian TRIM5 orthologues is enhanced by CypA, and inhibition of CypA expression or of its activity partially rescues infectivity in restrictive conditions [21,26,28-30]. CypA binds to an exposed proline-rich loop on buy Aviptadil pubmed ID:https://www.ncbi.nlm.nih.gov/pubmed/25447644 the viral CA [31,32] and catalyzes the isomerisation of the peptide bond G89-P90 [33,34]. The mutation V86M in the CypA-binding loop of HIV-1 CA has been identified as conferring partial resistance to TRIM5rh [35]. The mechanism of HIV-1 resistance to TRIM5rh conferred by V86M CA was not addressed in this study. However, it was established that this mutation in the CypA-binding loop did not disrupt CA-CypA interactions in vitro or in cell cultures [35]. We and others have proposed that point mutations in the variable region 1 (v1) of TRIM5hu could confer HIV-1 restriction capability [36-41]. These mutations were discovered by mapping of HIV-1 restriction determinants in non-human TRIM5 orthologues [36,39-41] or through the use of random mutagenesis-based screens [38,42]. Such antiviral genes are promising candidates for gene therapy applications, owing to a few key characteristics: (i) They block replication early after virus entry and before integration can occur; (ii) They are human-like and thus probably nonimmunogenic; (iii) PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/27484364 They inhibit HIV-1 by a well-established, natural mechanism with little side effect expected. However, it is currently unknown whether HIV-1 can acquire resistance to TRIM5hu mutants. Here we investigate the extent and mechanism of resistance of the HIV-1 CA mutant V86M to R332GR335G TRIM5hu and other mutants of the v1 domain. Our data show that this mutation affects physical andfunctional interactions with CypA in order to decrease HIV-1 sensitivity to TRIM5 while retaining replicationenhancement functions also conferred by CypA binding.ResultsCA-V86M HIV-1 is partially resistant to restriction by TRIM5hu mutant R332G-R335GWe analyzed whether V86M could protect HIV-1 against restriction by TRIM5hu mutant R332G-R335G in human TE671, human Sup-T1 and feline CRFK cells. The choice of human cells as an experimental model was justified by the need to gather data in cells representative of the HIV1 natural host, while the analysis in cat cells was prompted by the absence of an endogenous TRIM5 protein in this species, thus allowing us to analyz.

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