Modulation of chromatin structure by the FACT histone chaperone complex regulates HIV-1 integration

Abstract

BackgroundInsertion of retroviral genome DNA occurs in the chromatin of the host cell. This step is modulated by chromatin structure as nucleosomes compaction was shown to prevent HIV-1 integration and chromatin remodeling has been reported to affect integration efficiency. LEDGF/p75-mediated targeting of the integration complex toward RNA polymerase II (polII) transcribed regions ensures optimal access to dynamic regions that are suitable for integration. Consequently, we have investigated the involvement of polII-associated factors in the regulation of HIV-1 integration.ResultsUsing a pull down approach coupled with mass spectrometry, we have selected the FACT (FAcilitates Chromatin Transcription) complex as a new potential cofactor of HIV-1 integration. FACT is a histone chaperone complex associated with the polII transcription machinery and recently shown to bind LEDGF/p75. We report here that a tripartite complex can be formed between HIV-1 integrase, LEDGF/p75 and FACT in vitro and in cells. Biochemical analyzes show that FACT-dependent nucleosome disassembly promotes HIV-1 integration into chromatinized templates, and generates highly favored nucleosomal structures in vitro. This effect was found to be amplified by LEDGF/p75. Promotion of this FACT-mediated chromatin remodeling in cells both increases chromatin accessibility and stimulates HIV-1 infectivity and integration.ConclusionsAltogether, our data indicate that FACT regulates HIV-1 integration by inducing local nucleosomes dissociation that modulates the functional association between the incoming intasome and the targeted nucleosome.Electronic supplementary materialThe online version of this article (doi:10.1186/s12977-017-0363-4) contains supplementary material, which is available to authorized users.

Curaxin CBL0137 has the potential to reverse HIV‐1 latency

“…CBL0137 blocked viral replication to the same extent as CBL0100 without any cytotoxicity (Figure S2). However, these results contrast with Matysiak et al's paper, which showed that CBL0137 targeting of the FACT complex facilitated HIV‐1 integration by 1.5‐fold and enhanced early steps of HIV‐1 replication. Nevertheless, the emphasis was strictly put on studying FACT at the integration step and these experiments were limited to HeLa or HEK293 cells, which do not recapitulate the cellular tropism of HIV‐1.…”

“…Using Spina et al's article on the evaluation of antilatency drugs (where the viability of compounds ranged from 69% to 96%), a concentration of CBL0137 maintaining cell death less than or equal to 10% (CC 10 ) across all cell lines was selected 0.5 µM (Table S2). Interestingly, this concentration was also used by another group for CBL0137 in a report investigating the importance of FACT complex in HIV‐1 integration …”

“…Thus, future studies targeting components in these pathways could provide mechanistic insights for CBL0137. Alternatively, CBL0137 was reported to increase chromatin accessibility by intercalating into DNA and disrupting proper DNA/protein interactions by a process termed “c‐trapping” . Therefore, hypothetically CBL0137 could further enhance HIV‐1 reactivation by increasing chromatin accessibility, which could allow for easier recruitment/processivity of the general transcriptional machinery, at an already “sensitized” HIV‐1 locus due to TNF‐α .…”

“…Interestingly, another curaxin, CBL0137, has been implicated in promoting HIV integration. Its mechanism of action involves FACT‐mediated destabilization of chromatin nucleosomes to favor viral genome entry into newly accessible DNA . However, there are no studies looking at the effects of CBL0137 in the context of HIV‐1 latency.…”

Les facteurs du pore nucléaire : un collectif gagnant pour la translocation et l’intégration du VIH-1

“…La région C-terminale de la protéine NUP153, contenant 29 motifs FG, est responsable de l'interaction avec la capside du VIH-1 [6]. De [10]. Si le facteur LEDGF/p75 permet une intégration dans des zones précises du génome de l'hôte, il a été montré que ce n'est pas la seule protéine à faciliter l'amarrage des complexes viraux à la chromatine : il semble que d'autres facteurs participent également à cette fonction.…”