Demonstration of enzyme activities required for cap structure formation in infectious bursal disease virus, a member of the birnavirus group

Spies, U.; Müller, Hermann

doi:10.1099/0022-1317-71-4-977

Cited by 55 publications

(22 citation statements)

References 36 publications

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“…The smaller segment, B, encodes VP1, a 97-kDa multifunctional protein with polymerase and capping enzyme activities (40). The larger segment, A, contains a large open reading frame (ORF) encoding a 110-kDa precursor protein that is processed into mature VP2 and VP3 structural proteins by the viral protease, VP4 (2,20,21).…”

Section: Infectious Bursal Disease Virus (Ibdv) Is the Causative Agenmentioning

confidence: 99%

Nonstructural Protein of Infectious Bursal Disease Virus Inhibits Apoptosis at the Early Stage of Virus Infection

Liu

Vakharia

2006

J Virol

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Infectious bursal disease virus (IBDV), the causative agent of a highly contagious disease in chickens, carries a small nonstructural protein (NS). This protein has been implicated to play a role in the induction of apoptosis. In this study, we investigate the kinetics of viral replication during a single round of viral replication and examine the mechanism of IBDV-induced apoptosis. Our results show that it is caspase dependent and activates caspases 3 and 9. Nuclear factor kappa B (NF-B) is also activated and is required for IBDV-induced apoptosis. The NF-B inhibitor MG132 completely inhibited IBDV-induced DNA fragmentation, caspase 3 activation, and NF-B activation. To study the function of the NS protein in this context, we generated the recombinant rGLS virus and an NS knockout mutant, rGLSNS⌬ virus, using reverse genetics. Comparisons of the replication kinetics and markers for virally induced apoptosis indicated that the NS knockout mutant virus induces earlier and increased DNA fragmentation, caspase activity, and NF-B activation. These results suggest that the NS protein has an antiapoptotic function at the early stage of virus infection.

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Section: Infectious Bursal Disease Virus (Ibdv) Is the Causative Agenmentioning

confidence: 99%

Nonstructural Protein of Infectious Bursal Disease Virus Inhibits Apoptosis at the Early Stage of Virus Infection

Liu

Vakharia

2006

J Virol

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“…Although the protein primer and the polymerase are usually two separate molecular moieties, the protein priming function in birnaviruses is carried out by the RNA-dependent RNA polymerase VP1 itself. It has been shown that both virion-associated and recombinant birnavirus VP1 have the self-guanylylation activity (12,17,22,26). VP1 selfguanylylation, which does not require viral RNA template, produces two products, 17,22,26).…”

mentioning

confidence: 99%

“…It has been shown that both virion-associated and recombinant birnavirus VP1 have the self-guanylylation activity (12,17,22,26). VP1 selfguanylylation, which does not require viral RNA template, produces two products, 17,22,26). It has been proposed that the pGpG moiety in VP1-pGpG binds to the conserved pCpC sequence at the terminal end of the viral RNA template during the initiation of nucleotide polymerization (17, 27).…”

mentioning

confidence: 99%

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The structure of a birnavirus polymerase reveals a distinct active site topology

Pan

Vakharia

Tao

2007

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

109

130

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Single-subunit polymerases are universally encoded in both cellular organisms and viruses. Their three-dimensional structures have the shape of a right-hand with the active site located in the palm region, which has a topology similar to that of the RNA recognition motif (RRM) found in many RNA-binding proteins. Considering that polymerases have well conserved structures, it was surprising that the RNA-dependent RNA polymerases from birnaviruses, a group of dsRNA viruses, have their catalytic motifs arranged in a permuted order in sequence. Here we report the 2.5 Å structure of a birnavirus VP1 in which the polymerase palm subdomain adopts a new active site topology that has not been previously observed in other polymerases. In addition, the polymerase motif C of VP1 has the sequence of -ADN-, a highly unusual feature for RNA-dependent polymerases. Through site-directed mutagenesis, we have shown that changing the VP1 motif C from -ADN-to -GDD-results in a mutant with an increased RNA synthesis activity. Our results indicate that the active site topology of VP1 may represent a newly developed branch in polymerase evolution, and that birnaviruses may have acquired the -ADN-mutation to control their growth rate.evolution ͉ virus ͉ RdRp S ingle-subunit polymerases, including RNA/DNA-dependent RNA/DNA polymerases, are universally encoded in cellular organisms and viruses. Sequence analysis shows that RNAdependent RNA polymerases (RdRps) are a cluster of closely related enzymes that are mostly found in viruses, in which they assume critical functional roles by replicating and transcribing viral genome. The recently reported crystal structures of several RdRps and their functional complexes have provided important insights into the biological functions and catalytic mechanisms of these enzymes (1-10). These structures contain a well conserved core polymerase domain, the shape of which resembles a right hand with fingers, palm, and thumb subdomains. The palm, which is the most conserved region, contains a central, nonvariant, four-stranded ␤-sheet with five recurring catalytic sequence motifs (from A to E).In contrast to these conventional features, birnavirus polymerase VP1 exhibits several unusual characteristics (11,12). Most noticeably, the essential -X(G)DD-sequence, which is often referred to as the polymerase motif C (13, 14), is missing from VP1 (12). This raises the question as to whether VP1 promotes catalysis by the two-metal mechanism like in conventional polymerases, or whether VP1 employs a different mechanism for nucleotidyl transfer. Recent results indicate that birnavirus VP1, as well as the polymerases from some tetraviruses, may belong to a special group of unconventional polymerases with five essential RNA polymerase motifs arranged in the permuted order of C-A-B-D-E (15). In addition, the motif C in birnaviruses may have the sequence -ADN-, resulting in only two aspartate residues in the active site (15).Like polymerases from other dsRNA viruses, birnavirus VP1 catalyzes both replication and transc...

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“…This protein contains a consensus RNA-dependent RNA polymerase motif (8). Furthermore, this protein has been reported to be linked to the 5Ј ends of the genomic RNA segments (viral protein genome linked; VPg) (12,29).…”

mentioning

confidence: 99%

Rescue of Very Virulent and Mosaic Infectious Bursal Disease Virus from Cloned cDNA: VP2 Is Not the Sole Determinant of the Very Virulent Phenotype

Boot¹,

Huurne²,

Hoekman³

et al. 2000

J Virol

114

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Many recent outbreaks of infectious bursal disease in commercial chicken flocks worldwide are due to the spread of very virulent strains of infectious bursal disease virus (vvIBDV). The molecular determinants for the enhanced virulence of vvIBDV compared to classical IBDV are unknown. The lack of a reverse genetics system to rescue vvIBDV from its cloned cDNA hampers the identification and study of these determinants. In this report we describe, for the first time, the rescue of vvIBDV from its cloned cDNA. Two plasmids containing a T7 promoter and either the full-length A-or B-segment cDNA of vvIBDV (D6948) were cotransfected into QM5 cells expressing T7 polymerase. The presence of vvIBDV could be detected after passage of the transfection supernatant in either primary bursa cells (in vitro) or embryonated eggs (in vivo), but not QM5 cells. Rescued vvIBDV (rD6948) appeared to have the same virulence as the parental isolate, D6948. Segment-reassorted IBDV, in which one of the two genomic segments originated from cDNA of classical attenuated IBDV CEF94 and the other from D6948, could also be rescued by using this system. Segment-reassorted virus containing the A segment of the classical attenuated isolate (CEF94) and the B segment of the very virulent isolate (D6948) is not released until 15 h after an in vitro infection. This indicates a slightly retarded replication, as the first release of CEF94 is already found at 10 h after infection. Next to segment reassortants, we generated and analyzed mosaic IBDVs (mIBDVs). In these mIBDVs we replaced the region of CEF94 encoding one of the viral proteins (pVP2, VP3, or VP4) by the corresponding region of D6948. Analysis of these mIBDV isolates showed that tropism for non-B-lymphoid cells was exclusively determined by the viral capsid protein VP2. However, the very virulent phenotype was not solely determined by this protein, since mosaic virus containing VP2 of vvIBDV induced neither morbidity nor mortality in young chickens.

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Demonstration of enzyme activities required for cap structure formation in infectious bursal disease virus, a member of the birnavirus group

Cited by 55 publications

References 36 publications

Nonstructural Protein of Infectious Bursal Disease Virus Inhibits Apoptosis at the Early Stage of Virus Infection

Nonstructural Protein of Infectious Bursal Disease Virus Inhibits Apoptosis at the Early Stage of Virus Infection

The structure of a birnavirus polymerase reveals a distinct active site topology

Rescue of Very Virulent and Mosaic Infectious Bursal Disease Virus from Cloned cDNA: VP2 Is Not the Sole Determinant of the Very Virulent Phenotype

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