The coat protein of the yeast double-stranded RNA virus L-A attaches covalently to the cap structure of eukaryotic mRNA.

Blanc, A; Goyer, C; Sonenberg, Nahum

doi:10.1128/mcb.12.8.3390

Cited by 49 publications

(47 citation statements)

References 33 publications

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“…4B). Decapping activity has also been demonstrated in Gag of L-BC virus (14). Therefore, it is likely that the cap-snatching mechanism of L-A virus is widespread among totiviruses of fungi.…”

Section: Discussionmentioning

confidence: 96%

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Cap-snatching mechanism in yeast L-A double-stranded RNA virus

Fujimura

Esteban

2011

Proc. Natl. Acad. Sci. U.S.A.

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The 5′ cap structure (m 7 GpppX-) is an essential feature of eukaryotic mRNA required for mRNA stability and efficient translation. Influenza virus furnishes its mRNA with this structure by a capsnatching mechanism, in which the viral polymerase cleaves host mRNA endonucleolytically 10-13 nucleotides from the 5′ end and utilizes the capped fragment as a primer to synthesize viral transcripts. Here we report a unique cap-snatching mechanism by which the yeast double-stranded RNA totivirus L-A furnishes its transcript with a cap structure derived from mRNA. Unlike influenza virus, L-A transfers only m 7 Gp from the cap donor to the 5′ end of the viral transcript, thus preserving the 5′ α-and β-phosphates of the transcript in the triphosphate linkage of the final product. This in vitro capping reaction requires His154 of the coat protein Gag, a residue essential for decapping of host mRNA and known to form m 7 Gp-His adduct. Furthermore, the synthesis of capped viral transcripts in vivo and their expression were greatly compromised by the Arg154 mutation, indicating the involvement of Gag in the cap-snatching reaction. The overall reaction and the structure around the catalytic site in Gag resemble those of guanylyltransferase, a key enzyme of cellular mRNA capping, suggesting convergent evolution. Given that Pol of L-A is confined inside the virion and unable to access host mRNA in the cytoplasm, the structural protein Gag rather than Pol catalyzing this unique cap-snatching reaction exemplifies the versatility as well as the adaptability of eukaryotic RNA viruses.transcription | Saccharomyces cerevisiae | killer toxin E ukaryotic mRNA is capped at the 5′ end by a 7-methyl GMP moiety via an inverted 5′-5′ triphosphate linkage (m 7 GpppX) (1, 2). The cap structure is required for mRNA stability and efficient translation. Capping of the RNA 5′ end is accomplished in cells and for most viruses in three sequential catalytic reactions (3, 4): removal of the 5′ γ-phosphate by RNA triphosphatase, addition of GMP from GTP by guanylyltransferase, and methylation of the added GMP by methyltransferase. Influenza virus, how-

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Section: Discussionmentioning

confidence: 96%

“…Thus M1 can be maintained in the cell without the helper virus provided that L-A proteins are expressed from a vector (13). Two decades ago Blanc et al (14) found that the L-A coat protein Gag covalently binds the cap structure of mRNA. The reaction was inhibited by the cap analogue m 7 GpppG but not by the nonmethylated GpppG.…”

mentioning

confidence: 99%

Cap-snatching mechanism in yeast L-A double-stranded RNA virus

Fujimura

Esteban

2011

Proc. Natl. Acad. Sci. U.S.A.

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“…The double-stranded L-A virus, which infects yeast, employs a novel mechanism to decap cellular messages. The GAG capsid protein forms a covalent linkage to the RNA cap, promoting cap removal (37,38). Because L-A transcripts are not capped, the destabilized cellular RNA transcripts are thought to saturate the degradation machinery, allowing a portion of the L-A transcripts to escape degradation by cellular factors.…”

Section: Discussionmentioning

confidence: 99%

Vaccinia virus D10 protein has mRNA decapping activity, providing a mechanism for control of host and viral gene expression

Parrish

Resch

Moss

2007

Proc. Natl. Acad. Sci. U.S.A.

117

177

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Previous studies indicated that the vaccinia virus D10 protein, which is conserved in all sequenced poxviruses, participates in the rapid turnover of host and viral mRNAs. D10 contains a motif present in the family of Nudix/MutT enzymes, a subset of which has been shown to enhance mRNA turnover in eukaryotic cells through cleavage of the 5 cap (m 7 GpppNm-). Here, we demonstrate that a purified recombinant D10 fusion protein possesses an intrinsic activity that liberates m 7 GDP from capped RNA substrates. Furthermore, point mutations in the Nudix/MutT motif abolished decapping activity. D10 has a strong affinity for capped RNA substrates (K m Ϸ 3 nm). RNAs of 24 -309 nt were decapped to comparable extents, whereas the cap of a 12-nt RNA was uncleaved. At large molar ratios relative to capped RNA substrate, competitor m 7 GpppG, m 7 GTP, or m 7 GDP inhibited decapping, whereas even higher concentrations of unmethylated analogs did not. High concentrations of uncapped RNA were also inhibitory, suggesting that D10 recognizes its substrate through interaction with both cap and RNA moieties. Thus far, poxviruses represent the only virus family shown to encode a Nudix hydrolase-decapping enzyme. Although it may seem self-destructive for a virus to encode a decapping and a capping enzyme, accelerated mRNA turnover helps eliminate competing host mRNAs and allows stagespecific synthesis of viral proteins.mRNA metabolism ͉ MutT motif ͉ Nudix hydrolase ͉ poxvirus ͉ mRNA turnover T he steady-state concentration of an mRNA is determined by synthesis and decay, allowing cells to rapidly adapt their pattern of gene expression (1). Similarly, some viruses accelerate mRNA turnover to suppress synthesis of cellular proteins and regulate expression of their own genes (2). Studies of vaccinia virus (VACV), the laboratory prototype poxvirus, indicated that viral mRNAs are relatively unstable compared with those of uninfected cells (3, 4). Thus, rapid mRNA turnover coupled with robust and sequential transcription of viral early, intermediate, and late genes allow stage-specific protein synthesis (5). Likewise, VACV infection induces the destabilization of cellular transcripts, a process thought to contribute to the shutdown of host protein synthesis (6-9). The latter may enhance viral replication by alleviating competition from cellular mRNAs for the protein synthetic machinery and by diminishing host antiviral responses. Nevertheless, the mechanisms used by VACV to regulate mRNA turnover have not been elucidated.The VACV D9 and D10 proteins were identified as putative negative regulators of gene expression during a transfectionbased DNA library screen used to isolate activators of late VACV transcription (10, 11). Both proteins are highly conserved: D10 homologs are present in all sequenced poxviruses, and D9 homologs are in all members of the chordopoxvirus subfamily. Overexpression of D10 during infection significantly reduced the amount of VACV transcripts, and overexpression of D9 had a similar but lesser effect (11). Remarkabl...

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“…Gag covalently binds cap structures in vivo. When purified L-A viral particles are incubated with RNA containing a cap structure in the presence of magnesium, the His-154 residue of the L-A Gag protein becomes covalently bound to the m 7 GMP cap, releasing the uncapped mRNA (3,4). Mutations converting this residue to Arg, Asn, or Ser result in Gag proteins that bind caps but do not become covalently attached.…”

Section: Ski2p Ski3p and Ski8p Repress Translation Of Capmentioning

confidence: 99%

Decoying the Cap² mRNA Degradation System by a Double-Stranded RNA Virus and Poly(A)² mRNA Surveillance by a Yeast Antiviral System

Masison

Blanc

Ribas

et al. 1995

Molecular and Cellular Biology

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132

157

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The major coat protein of the L-A double-stranded RNA virus of Saccharomyces cerevisiae covalently binds m 7 GMP from 5 capped mRNAs in vitro. We show that this cap binding also occurs in vivo and that, while this activity is required for expression of viral information (killer toxin mRNA level and toxin production) in a wild-type strain, this requirement is suppressed by deletion of SKI1/XRN1/SEP1. We propose that the virus creates decapped cellular mRNAs to decoy the 533 exoribonuclease specific for cap ؊ RNA encoded by XRN1. The SKI2 antiviral gene represses the copy numbers of the L-A and L-BC viruses and the 20S RNA replicon, apparently by specifically blocking translation of viral RNA. We show that SKI2, SKI3, and SKI8 inhibit translation of electroporated luciferase and ␤-glucuronidase mRNAs in vivo, but only if they lack the 3 poly(A) structure. Thus, L-A decoys the SKI1/XRN1/SEP1 exonuclease directed at 5 uncapped ends, but translation of the L-A poly(A) ؊ mRNA is repressed by Ski2,3,8p. The SKI2-SKI3-SKI8 system is more effective against cap ؉ poly(A) ؊ mRNA, suggesting a (nonessential) role in blocking translation of fragmented cellular mRNAs.

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The coat protein of the yeast double-stranded RNA virus L-A attaches covalently to the cap structure of eukaryotic mRNA.

Cited by 49 publications

References 33 publications

Cap-snatching mechanism in yeast L-A double-stranded RNA virus

Cap-snatching mechanism in yeast L-A double-stranded RNA virus

Vaccinia virus D10 protein has mRNA decapping activity, providing a mechanism for control of host and viral gene expression

Decoying the Cap² mRNA Degradation System by a Double-Stranded RNA Virus and Poly(A)² mRNA Surveillance by a Yeast Antiviral System

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The coat protein of the yeast double-stranded RNA virus L-A attaches covalently to the cap structure of eukaryotic mRNA.

Cited by 49 publications

References 33 publications

Cap-snatching mechanism in yeast L-A double-stranded RNA virus

Cap-snatching mechanism in yeast L-A double-stranded RNA virus

Vaccinia virus D10 protein has mRNA decapping activity, providing a mechanism for control of host and viral gene expression

Decoying the Cap2 mRNA Degradation System by a Double-Stranded RNA Virus and Poly(A)2 mRNA Surveillance by a Yeast Antiviral System

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Decoying the Cap² mRNA Degradation System by a Double-Stranded RNA Virus and Poly(A)² mRNA Surveillance by a Yeast Antiviral System