Adenovirus Late Gene Expression Does Not Require a Rev-Like Nuclear RNA Export Pathway

Rabino, Claudia; Aspegren, Anders; Corbin-Lickfett, Kara; Bridge, Eileen

doi:10.1128/jvi.74.14.6684-6688.2000

Cited by 23 publications

(33 citation statements)

References 26 publications

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“…A subset of the short-lived cellular mRNAs characterized by the presence of AU-rich sequences in their 3Ј untranslated regions have been reported to leave the nucleus by the exportin 1 pathway (39). Previous studies have demonstrated that inhibition of exportin 1 does not impair synthesis of viral late protein (2,72) or of export of viral late mRNAs (35), despite the exportin 1-dependent shuttling of the E1B protein between the nucleus and cytoplasm (27,29,57). Rather, data reported here implicate Nxf1 in export of these viral mRNAs from the nucleus to the cytoplasm: synthesis in Ad5-infected cells of an interfering RNA that reduced the concentration of Nxf1, but not of a control nontargeting interfering RNA, results in decreased efficiency of export of viral late mRNA (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…This cellular protein contains an NES that is recognized by exportin 1 and binds to the human HuR protein, which has been identified as an export adaptor for certain unstable cellular mRNAs (12,39). Nevertheless, exportin 1 is not responsible for export of viral late mRNAs: treatment of infected cells with leptomycin B under conditions that blocked accumulation of the E1B 55-kDa protein in the cytoplasm had no impact on synthesis of viral late proteins (17,72). Furthermore, a cell-permeative peptide containing the HIV-1 Rev NES, but not an inactive derivative, significantly reduced the cytoplasmic accumulation of the E1B 55-kDa protein and inhibited its shuttling between the nucleus and cytoplasm (35), but it did not impair the efficiency with which processed major late (ML) penton or fiber mRNAs were exported from the nucleus (35).…”

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confidence: 99%

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Export of Adenoviral Late mRNA from the Nucleus Requires the Nxf1/Tap Export Receptor

Yatherajam

Wen-ying

Flint

2011

J Virol

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One important function of the human adenovirus E1B 55-kDa protein is induction of selective nuclear export of viral late mRNAs. This protein interacts with the viral E4 Orf6 and four cellular proteins to form an infected-cell-specific E3 ubiquitin ligase. The assembly of this enzyme is required for efficient viral late mRNA export, but neither the relevant substrates nor the cellular pathway that exports viral late mRNAs has been identified. We therefore examined the effects on viral late gene expression of inhibition of the synthesis or activity of the mRNA export receptor Nxf1, which was observed to colocalize with the E1B 55-kDa protein in infected cells. When production of Nxf1 was impaired by using RNA interference, the efficiency of viral late mRNA export was reduced to a corresponding degree. Furthermore, synthesis of a dominant-negative derivative of Nxf1 during the late phase of infection interfered with production of a late structural protein. These observations indicate that the Nxf1 pathway is responsible for export of viral late mRNAs. As the infectedcell-specific E3 ubiquitin ligase targets its known substrates for proteasomal degradation, we compared the concentrations of several components of this pathway (Nxf1, Thox1, and Thoc4) in infected cells that did or did not contain this enzyme. Although the concentration of a well-established substrate, Mre11, decreased significantly in cells infected by adenovirus type 5 (Ad5), but not in those infected by the E1B 55-kDa protein-null mutant Hr6, no E1B 55-kDa protein-dependent degradation of the Nxf1 pathway proteins was observed.During the late phase of productive infection by human species C adenovirus, such as adenovirus type 5 (Ad5), viral late mRNAs are exported selectively from the nucleus to the cytoplasm, with concomitant inhibition of export of the majority of cellular mRNAs (see references 6, 28, and 34 for reviews). Such regulation of mRNA export requires the viral E1B 55-kDa protein (3, 67, 71) and the complex it forms with the E4 Orf 6 protein (13,23,87). In both transformed and normal human cells, efficient export of viral late mRNAs correlates with the E4 Orf6 protein-dependent recruitment of the E1B protein to the peripheral zones of viral replication centers (40,41,66), which are the sites of synthesis and at least initial processing of viral late pre-mRNAs (2,14,68,69). In infected cells, the E1B 55-kDa and E4 Orf6 proteins associate with the cellular proteins cullin 5, elongins B and C, and Rbx to form an E3 ubiquitin ligase (46). Substrates of the infected-cell-specific ubiquitin ligase include the cellular p53 protein (21,46,61,71), the Mre11, Rad50, and Nbs1 components of the MRN complex (85), DNA ligase IV (5), and integrins ␣3 (25), which are targeted for proteasomal degradation. The infected-cell-specific ligase has also been implicated in regulation of mRNA export during the late phase of infection. Synthesis in infected cells of a dominant-negative derivative of cullin 5 that stabilized p53 and Mre11 resulted in decreases in ...

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Export of Adenoviral Late mRNA from the Nucleus Requires the Nxf1/Tap Export Receptor

Yatherajam

Wen-ying

Flint

2011

J Virol

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“…On the other hand, it has also been reported that the E4 Orf 6 NES failed to direct efficient export of a heterologous protein and that export of this E4 protein is insensitive to leptomycin B (26,58). Regardless of whether the E4 Orf 6 protein leaves the nucleus via the exportin 1 pathway, there is clear evidence that this export receptor does not mediate export of viral late mRNAs: the inhibition of exportin 1 by leptomycin B or an NES containing peptide had no effect on synthesis of viral late proteins (15,78) or viral late mRNA export (34).…”

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confidence: 96%

“…It has also been reported that the E4 Orf 6 protein contains a similar NES necessary for exportin-dependent shuttling of the E1B 55-kDa-E4 Orf 6 protein complex and sufficient to allow export when fused to an heterologous protein (24). The specific inhibitor of exportin 1, leptomycin B, has been observed to inhibit shuttling of this E4 protein substantially (78). On the other hand, it has also been reported that the E4 Orf 6 NES failed to direct efficient export of a heterologous protein and that export of this E4 protein is insensitive to leptomycin B (26,58).…”

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confidence: 99%

Adenovirus E1B 55-Kilodalton Protein Is Required for both Regulation of mRNA Export and Efficient Entry into the Late Phase of Infection in Normal Human Fibroblasts

González

Wen-ying

Finnen

et al. 2006

J Virol

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The human adenovirus type 5 (Ad5) E1B 55-kDa protein is required for selective nuclear export of viral late mRNAs from the nucleus and concomitant inhibition of export of cellular mRNAs in HeLa cells and some other human cell lines, but its contributions(s) to replication in normal human cells is not well understood. We have therefore examined the phenotypes exhibited by viruses carrying mutations in the E1B 55-kDa protein coding sequence in normal human fibroblast (HFFs). Ad5 replicated significantly more slowly in HFFs than it does in tumor cells, a difference that is the result of delayed entry into the late phase of infection. The A143 mutation, which specifically impaired export of viral late mRNAs from the nucleus in infected HeLa cells (R. During the late phase of human adenovirus type 5 (Ad5) infection, cellular protein synthesis is severely inhibited, while viral late proteins are made in large quantities (3, 6). Such preferential expression of viral genes is the result of posttranscriptional regulatory mechanisms: several viral gene products, including VA-RNA1 and the L4 100-kDa protein, contribute to selective translation of viral late mRNAs (see references 18, 64, and 85 for reviews), while the E1B 55-kDa and E4 Orf 6 proteins induce selective export of these mRNAs from the nucleus (reviewed in references 25, 33, and 39). In infected cells, these last two early proteins form a complex (84) that has been implicated in regulation of mRNA export (12, 19). Indeed, the E1B 55-kDa and E4 Orf 6 proteins colocalize to specific sites within infected cell nuclei, the peripheral zones of replication centers (70). Transcription of viral late genes and at least initial processing of viral pre-mRNAs take place at these same sites (4,14,74,75). Mutations that prevent synthesis of the E4 Orf 6 protein or reduce binding of this to the E1B 55-kDa protein (83) result in both mislocalization of the E1B 55-kDa protein and defects in export of viral late mRNAs (39, 70). These properties indicate that E4 Orf 6 protein-dependent recruitment of the E1B protein to the specialized nuclear sites at which viral late pre-mRNAs are synthesized promotes selective export of the processed mRNAs. The observation that the accumulation of viral mRNAs at enlarged interchromatin granules, which form in infected cells as the late phase progresses, correlates with efficient late mRNA export (4, 13) provides further support for the view that efficient mRNA export is intimately coupled to the organization of infected cell nuclei. However, the molecular basis of such coupling remains unknown, nor has the cellular export pathway by which viral late mRNAs are transported from the nucleus to the cytoplasm been identified.AThe E1B 55-kDa protein contains a leucine-rich nuclear export signal (NES) that is recognized by the cellular exportin 1 export receptor and mediates shuttling of the viral protein when it is synthesized either alone or in Ad5-infected cells (26,58). It has also been reported that the E4 Orf 6 protein contains a similar NES nece...

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“…E4orf6 is a nuclear protein containing both nuclear localization and nuclear retention signals that are believed to be responsible for targeting E4orf6 and E4orf6/E1B55K complexes to the nucleus (Goodrum et al 1996;Orlando and Ornelles 1999;Nevels et al 2000). In addition, both E4orf6 and E1B55K have nuclear export signals, and several groups have shown they can shuttle between the nucleus and the cytoplasm (Dobbelstein et al 1997;Weigel and Dobbelstein 2000;Rabino et al 2000;Dosch et al 2001).…”

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confidence: 99%

Degradation of p53 by adenovirus E4orf6 and E1B55K proteins occurs via a novel mechanism involving a Cullin-containing complex

Querido¹,

Blanchette²,

Yan³

et al. 2001

Genes Dev.

435

471

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Although MDM2 plays a major role in regulating the stability of the p53 tumor suppressor protein, other poorly understood MDM2-independent pathways also exist. Human adenoviruses have evolved strategies to regulate p53 function and stability to permit efficient viral replication. One mechanism involves adenovirus E1B55K and E4orf6 proteins, which collaborate to target p53 for degradation. To determine the mechanism of this process, a multiprotein E4orf6-associated complex was purified and shown to contain a novel Cullin-containing E3 ubiquitin ligase that is (1) composed of Cullin family member Cul5, Elongins B and C, and the RING-H2 finger protein Rbx1(ROC1); (2) remarkably similar to the von Hippel-Lindau tumor suppressor and SCF (Skp1-Cul1/Cdc53-F-box) E3 ubiquitin ligase complexes; and (3) capable of stimulating ubiquitination of p53 in vitro in the presence of E1/E2 ubiquitin-activating and -conjugating enzymes. Cullins are activated by NEDD8 modification; therefore, to determine whether Cullin complexes are required for adenovirus-induced p53 degradation, studies were conducted in ts41 Chinese hamster ovary cells that are temperature sensitive for the NEDD8 pathway. E4orf6/E1B55K failed to induce the degradation of p53 at the nonpermissive temperature. Thus, our results identify a novel role for the Cullin-based machinery in regulation of p53.

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Adenovirus Late Gene Expression Does Not Require a Rev-Like Nuclear RNA Export Pathway

Cited by 23 publications

References 26 publications

Export of Adenoviral Late mRNA from the Nucleus Requires the Nxf1/Tap Export Receptor

Export of Adenoviral Late mRNA from the Nucleus Requires the Nxf1/Tap Export Receptor

Adenovirus E1B 55-Kilodalton Protein Is Required for both Regulation of mRNA Export and Efficient Entry into the Late Phase of Infection in Normal Human Fibroblasts

Degradation of p53 by adenovirus E4orf6 and E1B55K proteins occurs via a novel mechanism involving a Cullin-containing complex

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