Reply to: No effect of endogenous TRIM5α on HIV-1 production

Sakuma, Ryuta; Ohmine, Seiga; Mael, Amber A.; Noser, Josh A.; Ikeda, Yasuhiro

doi:10.1038/nm0308-236

Cited by 5 publications

(22 citation statements)

References 8 publications

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“…In addition to their effects on early postentry events, both overexpression of rhesus TRIM5␣ and overexpression of human TRIM5␣ have been reported to specifically inhibit the late-phase production of infectious HIV-1 strains (35,36,50,51), and some (35,51), but not all (50), of these studies have found that inhibiting TRIM5 expression by using siRNA constructs targeting sequences common to all TRIM5 isoforms improves HIV-1 production in cells expressing physiological levels of rhesus or human TRIM5. In this context, Sakuma et al (36) reported that a truncated version of rhesus TRIM5 lacking the SPRY domain retained the ability to inhibit HIV-1 production. These findings raise the possibility that TRIM5 isoforms without SPRY domains could exercise late restriction activity, but further studies are needed to evaluate this possibility.…”

Section: Discussionmentioning

confidence: 99%

Modulation of TRIM5α Activity in Human Cells by Alternatively Spliced TRIM5 Isoforms

Battivelli

Migraine

Lecossier

et al. 2011

J Virol

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TRIM5␣ is a restriction factor that can block an early step in the retroviral life cycle by recognizing and causing the disassembly of incoming viral capsids, thereby preventing the completion of reverse transcription. Numerous other isoforms of human TRIM5 exist, and isoforms lacking a C-terminal SPRY domain can inhibit the activity of TRIM5␣. Thus, TRIM5␣ activity in a given cell type could be dependent on the relative proportions of TRIM5 isoforms expressed, but little information concerning the relative expression of TRIM5 isoforms in human cells is available. In this study, we demonstrate that mRNAs coding for TRIM5␣ represent only 50% of total TRIM5 transcripts in human cell lines, CD4 ؉ T cells, and macrophages. Transcripts coding for, in order of abundance, TRIM5 (TRIM5-iota), a previously uncharacterized isoform, TRIM5␥, TRIM5␦, and TRIM5 are also present. Like TRIM5␥ and TRIM5␦, TRIM5 and TRIM5 do not inhibit HIV-1 replication, but both have dominant-negative activity against TRIM5␣. Specific knockdown of TRIM5 increases TRIM5␣ activity in human U373-X4 cells, indicating that physiological levels of expression of truncated TRIM5 isoforms in human cells can reduce the activity of TRIM5␣.Following the entry of retroviral capsids into the cytoplasm of target cells, they can encounter cellular restriction factors that block the early steps of the viral life cycle. One wellcharacterized early restriction factor is TRIM5␣ (22,27,41,46), whose recognition of the incoming capsid leads to rapid capsid disassembly, preventing the completion of reverse transcription (42). Human TRIM5␣ can potently inhibit N-tropic murine leukemia virus (N-MLV) (12,18,31,48) and moderately inhibit equine infectious anemia virus and feline immunodeficiency virus replication (8,18,33). The infectivity of laboratory-adapted strains of HIV-1 is inhibited only 2-to 3-fold by the physiological levels of human TRIM5␣ expressed in human cells (13,17,39,44,49), but HIV-1 expressing capsid proteins derived from clinical isolates can be considerably more sensitive to human TRIM5␣, especially if TRIM5␣ expression in target cells is augmented by pretreatment with alpha interferon (IFN-␣) (1).TRIM5␣ is the longest of numerous TRIM5 isoforms expressed in human cells (Fig. 1) and is composed of several distinct domains. The RING domain (coded by exon 2) expresses E3 ubiquitin ligase activity, is required for optimal antiviral activity, and contributes to the rapid turnover of TRIM5␣ (9,15,41). The function of the B-box 2 domain (coded by exon 2) is not fully understood, but amino acid changes in this region can influence TRIM5␣ turnover, higherorder self-association of TRIM5␣ dimers, the formation of TRIM5␣-containing cytoplasmic bodies, and antiviral activity (7,10,15,20). The coiled-coil domain (coded by exons 2 to 4) promotes the formation of homodimers and participates in capsid recognition (16,19,24,26,30). These three domains comprise the RING/B-box/coiled-coil (RBCC) tripartite motif characteristic of all TRIM proteins. Finally, TRIM5␣ als...

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Section: Discussionmentioning

confidence: 99%

Modulation of TRIM5α Activity in Human Cells by Alternatively Spliced TRIM5 Isoforms

Battivelli

Migraine

Lecossier

et al. 2011

J Virol

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“…Moreover, TRIM5␣ is rapidly degraded in cells exposed to a restriction-sensitive retrovirus, suggesting a role of proteasomal degradation in the restriction (5). Similar to other TRIM proteins, TRIM5␣ self-associates to form cytoplasmic bodies (11,16), which turn over rapidly by exchanging with free cytoplasmic TRIM5␣ as well as neighboring TRIM5␣ bodies (17).…”

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confidence: 99%

“…We and others (18,20) have shown that co-expression of the C-terminal hemagglutinin (HA)-tagged TRIM5␣rh with HIV-1 proviral plasmids reduces the yield of infectious virus up to 20 -100-fold, although the late restriction activity of endogenous TRIM5␣rh remains controversial (18,20). High levels of TRIM5␣rh showed potent antiviral activity on HIV-1 production through degradation of Gag polyproteins, whereas modest TRIM5␣rh expression blocks HIV-1 production by reducing the virion infectivity as well as the yield of infectious virus (12,16). When HIV-1 production surpasses the late restriction activity, HIV-1 virions or virus-like particles (VLPs) produced in the presence of TRIM5␣rh protein incorporate high levels of intact and truncated forms of TRIM5␣rh (12,16).…”

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confidence: 99%

“…High levels of TRIM5␣rh showed potent antiviral activity on HIV-1 production through degradation of Gag polyproteins, whereas modest TRIM5␣rh expression blocks HIV-1 production by reducing the virion infectivity as well as the yield of infectious virus (12,16). When HIV-1 production surpasses the late restriction activity, HIV-1 virions or virus-like particles (VLPs) produced in the presence of TRIM5␣rh protein incorporate high levels of intact and truncated forms of TRIM5␣rh (12,16).…”

mentioning

confidence: 99%

“…When compared with TRIM5␣rh, human TRIM5␣ (TRIM5␣hu) shows marginal antiviral activity on HIV-1 production (12,16,18). Little or no encapsidation of TRIM5␣hu protein in HIV-1 virions or HIV-1 VLPs (12, 16) implies weaker interaction of HIV-1 Gag polyproteins with TRIM5␣hu than TRIM5␣rh.…”

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confidence: 99%

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Determinants for the Rhesus Monkey TRIM5α-mediated Block of the Late Phase of HIV-1 Replication

Sakuma

Ohmine

Ikeda

2010

Journal of Biological Chemistry

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Rhesus monkey TRIM5␣ (TRIM5␣rh) includes RING, B-box, coiled-coil, and B30.2(PRYSPRY) domains and blocks HIV-1 infection by targeting HIV-1 core through a B30.2(PRYSPRY) domain. Previously, we reported that TRIM5␣rh also blocks HIV-1 production in a B30.2(PRYSPRY)-independent manner. Efficient encapsidation of TRIM5␣rh, but not human TRIM5␣ (TRIM5␣hu), in HIV-1 virus-like particles suggests the interaction between Gag and TRIM5␣rh during viral assembly. Here, we determined responsible regions for late restriction activity of TRIM5␣rh. The RING disruption, but not the replacement with human TRIM21 RING, ablated the efficient encapsidation and the late restriction, suggesting that a RING structure was essential for the late restriction and efficient interaction with HIV-1 Gag. The prominent cytoplasmic body formation of TRIM5␣rh, which depended on the coiled-coil domain and the ensuing linker 2 region, was not required for the encapsidation. Intriguingly, TRIM5␣rh coiled-coil domain mutants (M133T and/or T146A) showed impaired late restriction activity, despite the efficient encapsidation and cytoplasmic body formation. Our results suggest that the TRIM5␣rh-mediated late restriction involves at least two distinct activities as follows: (i) interaction with HIV-1 Gag polyprotein through the N-terminal, RING, and B-box 2 regions of a TRIM5␣rh monomer, and (ii) an effector function(s) that depends upon the coiled-coil and linker 2 domains of TRIM5␣rh. We speculate that the TRIM5␣rh coiledcoil region recruits additional factor(s), such as other TRIM family proteins or a cellular protease, during the late restriction. RBCC domains of TRIM family proteins may play a role in sensing newly synthesized viral proteins as a part of innate immunity against viral infection.

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Potent restriction of HIV-1 and SIVmac239 Replication by African Green Monkey TRIM5α

et al. 2015

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BackgroundThe TRIM5α protein is a principal restriction factor that contributes to an HIV-1 replication block in rhesus macaque CD4+ T cells by preventing reverse transcription. HIV-1 restriction is induced in human CD4+ T cells by expression of rhesus TRIM5α as well as those of other old world monkeys. While TRIM5α restriction has been extensively studied in single-round infection assays, fewer studies have examined restriction after extended viral replication.ResultsTo examine TRIM5α restriction of replication, we studied the ability of TRIM5α proteins from African green monkey (AgmTRIM5α) and gorilla (gorTRIM5α) to restrict HIV-1 and SIVmac239 replication. These xenogeneic TRIM5α genes were transduced into human Jurkat-CCR5 cells (JR5), which were then exposed to HIV-1 or SIVmac239. In our single-round infection assays, AgmTRIM5α showed a relatively modest 4- to 10-fold restriction of HIV-1 and SIVmac239, while gorTRIM5α produced a 2- and 3-fold restriction of HIV-1 and SIVmac239, respectively, consistent with the majority of previously published single-round studies. To assess the impact of these modest effects on infection, we tested restriction in replication systems initiated with either cell-free or cell-to-cell challenges. AgmTRIM5α powerfully restricted both HIV-1 and SIVmac239 replication 14 days after cell-free infection, with a ≥ 3-log effect. Moreover, expression of AgmTRIM5α restricted HIV-1 and SIVmac239 replication by 2-logs when co-cultured with infected JR5 cells for 12 days. In contrast, neither expression of gorTRIM5α nor rhesus TRIM5α induced significant resistance when co-cultured with infected cells. Follow up experiments showed that the observed differences between replication and infection were not due to assembly defects as xenogeneic TRIM5α expression had no effect on either virion production or specific infectivity.ConclusionsOur results indicate that AgmTRIM5α has a much greater effect on extended replication than on any single infection event, suggesting that AgmTRIM5α restriction acts cumulatively, building up over many rounds of replication. Furthermore, AgmTRIM5α was able to potently restrict both HIV-1 and SIV replication in a cell-to-cell infection challenge. Thus, AgmTRIM5α is unique among the TRIM5α species tested to date, being able to restrict even at the high multiplicities of infection presented by mixed culture with nonrestrictive infected cells.

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Reply to: No effect of endogenous TRIM5α on HIV-1 production

Cited by 5 publications

References 8 publications

Modulation of TRIM5α Activity in Human Cells by Alternatively Spliced TRIM5 Isoforms

Modulation of TRIM5α Activity in Human Cells by Alternatively Spliced TRIM5 Isoforms

Determinants for the Rhesus Monkey TRIM5α-mediated Block of the Late Phase of HIV-1 Replication

Potent restriction of HIV-1 and SIVmac239 Replication by African Green Monkey TRIM5α

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