TAP, the Human Homolog of Mex67p, Mediates CTE-Dependent RNA Export from the Nucleus

Grüter, Patric; Tabernero, Carlos; Kobbe, Cayetano von; Schmitt, Christel; Saavedra, Claudio A.; Bachi, Ángela; Wilm, Matthias; Felber, Barbara K.; Izaurralde, Elisa

doi:10.1016/s1097-2765(00)80065-9

Cited by 523 publications

(549 citation statements)

References 39 publications

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“…In contrast, most cellular mRNAs are exported from the nucleus via NXF1/NXT. This pathway is exploited by the simple orthoretrovirus MasonPfizer monkey virus (MMPV), which has a constitutive RNA transport element (CTE) that recruits NXF1 directly (4,19).The trafficking itinerary and assembly competence of HIV-1 Gag can be influenced by the nuclear export history of the mRNA from which it is translated (1, 25, 52). If the HIV-1 RRE is replaced by the MPMV CTE, the normally Rev-dependent unspliced RNA exits the nucleus efficiently, but Gag translation is inefficient (7).…”

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Feline Immunodeficiency Virus Gag Is a Nuclear Shuttling Protein

Kemler

Saenz

Poeschla

2012

J Virol

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Lentiviral genomic RNAs are encapsidated by the viral Gag protein during virion assembly. The intracellular location of the initial Gag-RNA interaction is unknown. We previously observed feline immunodeficiency virus (FIV) Gag accumulating at the nuclear envelope during live-cell imaging, which suggested that trafficking of human immunodeficiency virus type 1 (HIV-1) and FIV Gag may differ. Here we analyzed the nucleocytoplasmic transport properties of both Gag proteins. We discovered that inhibition of the CRM1 nuclear export pathway with leptomycin B causes FIV Gag but not HIV-1 Gag to accumulate in the nucleus. Virtually all FIV Gag rapidly became intranuclear when the CRM1 export pathway was blocked, implying that most if not all FIV Gag normally undergoes nuclear cycling. In FIV-infected feline cells, some intranuclear Gag was detected in the steady state without leptomycin B treatment. When expressed individually, the FIV matrix (MA), capsid (CA), and nucleocapsid-p2 (NC-p2) domains were not capable of mediating leptomycin B-sensitive nuclear export of a fluorescent protein. In contrast, CA-NC-p2 did mediate nuclear export, with MA being dispensable. We conclude that HIV-1 and FIV Gag differ strikingly in a key intracellular trafficking property. FIV Gag is a nuclear shuttling protein that utilizes the CRM1 nuclear export pathway, while HIV-1 Gag is excluded from the nucleus. These findings expand the spectrum of lentiviral Gag behaviors and raise the possibility that FIV genome encapsidation may initiate in the nucleus.G ag is both necessary and sufficient for retrovirus particle formation and budding. The protein is translated on free polysomes and targeted to the plasma membrane, where virus particles are assembled (16). A central question is whether Gag and the viral genomic RNA (gRNA) associate at the plasma membrane or earlier during assembly and, if so, whether this occurs in the cytosol; in association with organelles, e.g., cotranslationally; or even in the nucleus, as was described previously for an alpharetrovirus (17). Human immunodeficiency virus type 1 (HIV-1) gRNAs become anchored at the plasma membrane before particle assembly is detectable, but it is not clear whether the Gag-gRNA complexes of this and other lentiviruses first form in the cytoplasm and then transit to the plasma membrane or the gRNA traffics there independently (26,27). Biochemical experiments supported the former scenario, with a monomer or low-order multimers forming on HIV-1 gRNAs and higher-order multimer formation depending on subsequent plasma membrane interactions (33).Gag is encoded by the full-length unspliced viral RNA. To circumvent the cellular checkpoint that prevents the export of intron-containing mRNA, lentiviruses express Rev, which functions as an adaptor between the cellular karyopherin CRM1/exportin-1 and a Rev response element (RRE) located in the 3= region of unspliced viral RNAs (9). However, the main cellular function of the CRM1 nuclear export pathway is the export of cellular proteins containing a...

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Feline Immunodeficiency Virus Gag Is a Nuclear Shuttling Protein

Kemler

Saenz

Poeschla

2012

J Virol

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“…None of the genes shows dramatic expression differences or changes in RNA size on Northern blots, but the neutral amino acid transporter gene Slc3a2 (also called Cd98, Mdu1, or 4F2), the mRNA export factor Nxf1 (Tap) and the chromatin remodeling complex component, Taf6l (Paf65a) show nonsynonymous substitutions in coding sequence or codon deletions (Taf6l) that suggest them as positional candidate genes. Interestingly, Nxf1 protein is known to mediate nuclear export of unspliced, CTE-containing RNAs 22 ; in principle this could explain both class-specific and orientation-specific effects of Mvb1, making Nxf1 a strong biological as well as positional candidate gene.…”

Section: Mvb1 Maps To a 210 Kb Interval Containing 11 Genes And A Recmentioning

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A natural allele of Nxf1 suppresses retrovirus insertional mutations

et al. 2003

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Endogenous retroviruses have shaped the evolution of mammalian genomes. Host genes that control the effects of retrovirus insertions are therefore of great interest. The Modifier-of-vibrator-1 locus controls level of correctly processed mRNA from genes mutated by endogenous retrovirus insertions into introns, including the pitpn vb tremor mutation and the Eya1 BOR model of human branchiootorenal syndrome. Positional complementation cloning identifies Mvb1 as the nuclear export factor Nxf1, providing an unexpected link between mRNA export receptor and pre-mRNA processing. Population structure of the suppressing allele in wild M. m. castaneus suggests selective advantage. A congenic Mvb1 CAST allele is a useful tool for modifying gene expression from existing mutations and could be used to manipulate engineered mutations containing retroviral elements.Mus musculus is a complex species group with subpopulations that have diverged and hybridized since becoming commensal with humans some 10,000 years ago. Allopatric divergence and re-hybridization of mouse lineages are thought to contribute to the diversity and activity of retroviral elements in the current mouse genomes 1,2 . Host genes that can NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript influence the expression of newly introduced (or newly mobilized) viral elements might be selected for variants that blunt these effects. Our results suggest that Mvb1 is such a locus.Mvb1 was originally identified as a strain-derived locus that modifies the neurological mutant, vibrator 3. The vibrator (vb) mutation is a hypomorphic allele of the phosphatidylinositol transfer protein α (PITPα) gene (pitpn) caused by the insertion of an endogenous retrovirus (intracisternal A particle, or IAP) into the fourth intron of the gene, resulting in 5 to 10-fold loss of PITPα expression. Homozygous vibrator mice show severe action tremor, progressive degeneration of interneurons in the brain stem and spinal cord, and uniform juvenile lethality. However, vibrator mice carrying Mvb1 alleles from the wild-derived CAST/Ei inbred strain show reduced tremor severity and survive to adulthood. In principle, this could be due to a change in physiological requirement for PITPα function or to a change in the steady-state expression level of PITPα derived from the mutant allele. RESULTS Mvb1 is a dosage-sensitive modifier of vibrator RNA accumulationMvb1 modifies the severity of vibrator tremor and the associated juvenile lethality 3 . To examine this effect in more detail, we monitored the longevity of vb mutant mice congenic on a C57BL/6J (B6) strain background with zero, one or two CAST/Ei alleles of Mvb1 ( Figure 1a). Consistent with our behavioral observations, the longevity data indicate a semi-dominant mode of action and high penetrance.To extend these observations to the cellular level, we examined histology of vibrator animals homozygous for either the B6 or CAST allele of Mvb1 (Figure 1b To ask whether Mvb1 acts by altering RNA levels from the mutant...

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“…27 In contrast, the constitutive transport element (CTE) of Mason-Pfizer monkey virus mediates the export of unspliced RNA through the cellular RNA export factor Tap. 28 We hypothesized that the export of partially doublestranded genomic bidirectional vector RNA depends on Rev's function to overcome nuclear quality control restrictions. Therefore, HIV-Rev dependency would restrict the usage of bidirectional expression cassettes to LV vectors.…”

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Mechanisms controlling titer and expression of bidirectional lentiviral and gammaretroviral vectors

et al. 2009

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Bidirectional lentiviral vectors mediate expression of two or more cDNAs from a single internal promoter. In this study, we examined mechanisms that control titer and expression properties of this vector system. To address whether the bidirectional design depends on lentiviral (LV) backbone components, especially the Rev/Rev responsive element (RRE) system, we constructed similar expression cassettes for LV and gammaretroviral (GV) vectors. Bidirectional expression levels could be adjusted by the use of different internal promoters. Furthermore, removal of the constitutive RNA transport element of Mason-Pfizer monkey virus, used in first generation bidirectional LV vectors, improved gene expression. Titers of bidirectional vectors were B10-fold reduced in comparison to unidirectional vectors, independent of the Rev/RRE interaction. We reasoned that titer reductions were due to the formation of interfering double-stranded RNA in packaging cells. Indeed, cotransfection of Nodamuravirus B2 protein, an RNA interference suppressor, increased bidirectional vector titers at least fivefold. We validated the potential of high titer bidirectional vectors by coexpressing a fluorescent marker with O 6 -methylguanine-DNA methyltransferase from integrating, or with Cre recombinase from integrating and non-integrating GV and LV backbones. This allowed for the tracking of chemoprotected and recombined cells by fluorescence marker expression.

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TAP, the Human Homolog of Mex67p, Mediates CTE-Dependent RNA Export from the Nucleus

Cited by 523 publications

References 39 publications

Feline Immunodeficiency Virus Gag Is a Nuclear Shuttling Protein

Feline Immunodeficiency Virus Gag Is a Nuclear Shuttling Protein

A natural allele of Nxf1 suppresses retrovirus insertional mutations

Mechanisms controlling titer and expression of bidirectional lentiviral and gammaretroviral vectors

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