Multiple components of the nuclear pore complex interact with the amino-terminus of MX2 to facilitate HIV-1 restriction

Dicks, Matthew D. J.; Betancor, Gilberto; Jiménez-Guardeño, Jose M.; Pessel-Vivares, Lucie; Apolonia, Luis; Goujon, Caroline; Malim, Michael H.

doi:10.1371/journal.ppat.1007408

Cited by 48 publications

(88 citation statements)

References 52 publications

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“…Antiviral functions of MX2 have been associated with its localization to the nuclear envelope; however, cytoplasmic localization has also been reported (Dicks et al, ; Melén et al, ). Cytoplasmic and nuclear fractionation of melanoma cell lines showed that MX2 protein is mainly found in the nuclear fraction, but a weak cytoplasmic localization was also detected (Figure g).…”

Section: Resultsmentioning

confidence: 99%

MX 2 is a novel regulator of cell cycle in melanoma cells

Juraleviciute

Poźniak

Nsengimana

et al. 2019

Pigment Cell Melanoma Res

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MX2 protein is a dynamin‐like GTPase2 that has recently been identified as an interferon‐induced restriction factor of HIV‐1 and other primate lentiviruses. A single nucleotide polymorphism (SNP), rs45430, in an intron of the MX2 gene, was previously reported as a novel melanoma susceptibility locus in genome‐wide association studies. Functionally, however, it is still unclear whether and how MX2 contributes to melanoma susceptibility and tumorigenesis. Here, we show that MX2 is differentially expressed in melanoma tumors and cell lines, with most metastatic cell lines showing lower MX2 expression than primary melanoma cell lines and melanocytes. Furthermore, high expression of MX2 RNA in primary melanoma tumors is associated with better patient survival. Overexpression of MX2 reduces in vivo proliferation partially through inhibition of AKT activation, suggesting that it can act as a tumor suppressor in melanoma. However, we have also identified a subset of melanoma cell lines with high endogenous MX2 expression where downregulation of MX2 leads to reduced proliferation. In these cells, MX2 downregulation interfered with DNA replication and cell cycle processes. Collectively, our data for the first time show that MX2 is functionally involved in the regulation of melanoma proliferation but that its function is context‐dependent.

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Section: Resultsmentioning

confidence: 99%

MX 2 is a novel regulator of cell cycle in melanoma cells

Juraleviciute

Poźniak

Nsengimana

et al. 2019

Pigment Cell Melanoma Res

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“…Thus, the association of MxB with nuclear pore structures (33)(34)(35)(36)(37) taken together with the demonstration of nuclear pore structures to be phase-separated condensates (51,52) points to the inference that MxB also associates with membraneless phase-separated condensates (see Figs.…”

Section: Discussionmentioning

confidence: 92%

“…Human MxA forms disparate membraneless structures solely in the cytoplasm and has antiviral activity towards several RNA-and DNA-containing viruses including orthomyxo-and rhabdoviruses (23)(24)(25)(26)(27)(28)(29), while human MxB is mainly associated with the cytoplasmic side of nuclear pores and additional cytoplasmic membraneless structures and the full-length MxB has antiviral activity against HIV and other lentiviruses by blocking entry of viral components into the nucleus (33)(34)(35)(36)(37). Murine Mx1 is mainly in nuclear bodies (it has a C-terminal nuclear localization signal), while murine Mx2 is mainly in cytoplasmic structures (23)(24)(25)(29)(30)(31).…”

Section: Introductionmentioning

confidence: 99%

Murine GFP-Mx1 forms phase-separated nuclear condensates and associates with cytoplasmic intermediate filaments: novel antiviral activity against vesicular stomatitis virus

Sehgal

Yuan

Scott

et al. 2020

Preprint

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Type I and III interferons (IFNs) induce expression of the “myxovirus resistance proteins” MxA in human cells and its ortholog Mx1 in murine cells. Human MxA forms cytoplasmic structures, some tethered to intermediate filaments. In contrast, murine Mx1 mainly forms nuclear bodies. Both HuMxA and MuMx1 are antiviral towards influenza A virus (FLUAV) (an orthomyxovirus). However, it has long been considered that HuMxA, but not MuMx1, was antiviral towards vesicular stomatitis virus (VSV) (a rhabdovirus). We previously reported that the cytoplasmic human GFP-MxA structures in Huh7 hepatoma cells were phase-separated membraneless organelles (MLOs) (“biomolecular condensates”). In the present study we investigated whether nuclear murine Mx1 structures might also represent phase-separated biomolecular condensates. The transient expression of murine GFP-Mx1 in Huh7 hepatoma and Mich-2H6 melanoma cells led to the appearance of Mx1 nuclear bodies. These GFP-MuMx1 nuclear bodies were rapidly disassembled by exposing cells to 1, 6-hexanediol (5% w/v), or to hypotonic buffer (40-50 mosM), consistent with properties of membraneless phase-separated condensates. FRAP assays revealed that the GFP-MuMx1 nuclear bodies upon photobleaching showed a slow partial recovery (mobile fraction: ∼18%) suggestive of a gel-like consistency. Surprisingly, expression of GFP-MuMx1 in Huh7 cells also led to the appearance of MuMx1 in a novel cytoplasmic giantin-based intermediate filament meshwork and in cytoplasmic structures in 20-30% of transiently transfected Huh7 cells. Remarkably, Huh7 cells with cytoplasmic murine GFP-MuMx1 filaments, but not those with only nuclear bodies, showed antiviral activity towards VSV. Thus, murine GFP-Mx1 nuclear bodies comprised phase-separated condensates. Unexpectedly, GFP-MuMx1 associated with cytoplasmic giantin-based intermediate filaments in a subset of Huh7 cells, and, such cells showed antiviral activity towards VSV.

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“…This basic phenotype, moreover, is observed upon restriction of WT virus by the antiviral protein MxB (61). Although MxB is unlikely to be expressed at tangible levels under the conditions of viral infection used herein, recent reports have implicated components of the cellular nuclear import machinery in the mechanism of MxB antiviral activity (85,86). We accordingly propose that analysis of the effects of MA-CA coassembly on Nup153 and Nup358 binding to CA in vitro or in cells in the presence or absence of MxB may help to inform the molecular mechanism of altered MA-CA integration site targeting observed here.…”

Section: Discussionmentioning

confidence: 74%

Dominant Negative MA-CA Fusion Protein Is Incorporated into HIV-1 Cores and Inhibits Nuclear Entry of Viral Preintegration Complexes

Anderson-Daniels

Singh

Sowd

et al. 2019

J Virol

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Particle maturation is a critical step in the HIV-1 replication cycle that requires proteolytic cleavage of the Gag polyprotein into its constitutive proteins: the matrix (MA), capsid (CA), nucleocapsid (NC), and p6 proteins. The accurate and efficient cleavage of Gag is essential for virion infectivity; inhibitors of the viral protease are potent antivirals, and substitutions in Gag that prevent its cleavage result in reduced HIV-1 infectivity. In a previous study, a mutation inhibiting cleavage at the MA-CA junction was observed to potently inhibit virus infection: incorporation of small amounts of uncleaved MA-CA protein into HIV-1 particles inhibited infectivity by ∼95%, and the resulting viral particles exhibited aberrant capsids. Here we report a detailed mechanistic analysis of HIV-1 particles bearing uncleaved MA-CA protein. We show that the particles contain stable cores and can efficiently saturate host restriction by TRIMCyp in target cells. We further show that MA-CA associates with CA in particles without detectably affecting the formation of intermolecular CA interfaces. Incorporation of MA-CA did not markedly affect reverse transcription in infected cells, but nuclear entry was impaired and integration targeting was altered. Additionally, results from mutational analysis of Gag revealed that membrane-binding elements of MA contribute to the antiviral activity of uncleaved MA-CA protein. Our results suggest that small amounts of partially processed Gag subunits coassemble with CA during virion maturation, resulting in impaired capsid functions. IMPORTANCE To become infectious, newly formed HIV-1 particles undergo a process of maturation in which the viral polyproteins are cleaved into smaller components. A previous study demonstrated that inclusion of even small quantities of an uncleavable mutant Gag polyprotein results in a strong reduction in virus infectivity. Here we show that the mechanism of transdominant inhibition by uncleavable Gag involves inhibition of nuclear entry and alteration of viral integration sites. Additionally, the results of mutational analysis suggest that the membrane-binding activity of Gag is a major requirement for the antiviral activity. These results further define the antiviral mechanism of uncleavable Gag, which may be useful for exploiting this effect to develop new antivirals.

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Multiple components of the nuclear pore complex interact with the amino-terminus of MX2 to facilitate HIV-1 restriction

Cited by 48 publications

References 52 publications

MX 2 is a novel regulator of cell cycle in melanoma cells

MX 2 is a novel regulator of cell cycle in melanoma cells

Murine GFP-Mx1 forms phase-separated nuclear condensates and associates with cytoplasmic intermediate filaments: novel antiviral activity against vesicular stomatitis virus

Dominant Negative MA-CA Fusion Protein Is Incorporated into HIV-1 Cores and Inhibits Nuclear Entry of Viral Preintegration Complexes

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