Structure of the vesicular stomatitis virus nucleoprotein-RNA complex.
ABSTRACT Vesicular stomatitis virus is a negative-stranded RNA virus. Its nucleoprotein (N) binds the viral genomic RNA and is involved in multiple functions including transcription, replication, and assembly. We have determined a 2.9 angstrom structure of a complex containing 10 molecules of the N protein and 90 bases of RNA. The RNA is tightly sequestered in a cavity at the interface between two lobes of the N protein. This serves to protect the RNA in the absence of polynucleotide synthesis. For the RNA to be accessed, some conformational change in the N protein should be necessary.
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ABSTRACT: It is well established that RNA viruses exhibit higher rates of spontaneous mutation than DNA viruses and microorganisms. However, their mutation rates vary amply, from 10(-6) to 10(-4) substitutions per nucleotide per round of copying (s/n/r) and the causes of this variability remain poorly understood. In addition to differences in intrinsic fidelity or error correction capability, viral mutation rates may be dependent on host factors. Here, we assessed the effect of the cellular environment on the rate of spontaneous mutation of the vesicular stomatitis virus (VSV), which has a broad host range and cell tropism. Luria-Delbrück fluctuation tests and sequencing showed that VSV mutated similarly in baby hamster kidney, murine embryonic fibroblasts, colon cancer, and neuroblastoma cells (approx. 10(-5) s/n/r). Cell immortalization through p53 inactivation and oxygen levels (1-21%) did not have a significant impact on viral replication fidelity. This shows that previously published mutation rates can be considered reliable despite being based on a narrow and artificial set of laboratory conditions. Interestingly, we also found that VSV mutated approximately four times more slowly in various insect cells compared with mammalian cells. This may contribute to explaining the relatively slow evolution of VSV and other arthropod-borne viruses in nature.PLoS Pathogens 01/2014; 10(1):e1003855. · 8.14 Impact Factor
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ABSTRACT: The development of mechanistic insight into the molecular basis of how intrinsically disordered proteins function is a key challenge for contemporary molecular biology. Intrinsic protein disorder is abundant in the replication machinery of paramyxoviruses. In order to study this kind of protein, new methods are required that specifically take account of the highly dynamic nature of the chain, and describe this disorder in quantitative terms. Here we review recent studies of conformational disorder in paramyxoviral phosphoproteins and nucleoproteins using solution-based approaches such as nuclear magnetic resonance.Current opinion in virology. 03/2014; 5C:72-81.
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ABSTRACT: Birnaviruses are unconventional members of the icosahedral double-stranded (dsRNA) RNA virus group. The main differential birnavirus trait is the lack of the inner icosahedral transcriptional core, a ubiquitous structure conserved in all other icosahedral dsRNA viruses, that shelters the genome from cellular dsRNA sensors and provide the enzymatic machinery to produce and extrude mature messenger RNAs. In contrast, birnaviral particles enclose ribonucleoprotein (RNP) complexes formed by the genome segments, the dsRNA-binding VP3 polypeptide and the virus-encoded RNA polymerase (RdRp). The presence of RNPs suggests that the birnavirus replication program might exhibit significant differences with respect to those of prototypal dsRNA viruses. However, experimental evidences supporting this hypothesis are as yet scarce. Of particular relevance for the understanding of birnavirus replication is to determine whether RNPs act as intracellular capsid-independent transcriptional units. Our study was focused to answer this question using the infectious bursal disease virus (IBDV), the best characterized birnavirus, as model virus. Here, we describe the intracellular assembly of functional IBDV RNPs in the absence of the virus-encoded VP2 capsid polypeptide. Recombinant RNPs are generated upon coexpression of the IBDV VP1 and RdRp polypeptides and transfection of purified virus dsRNA. Presented data show that recombinant RNPs direct the expression of the IBDV polypeptide repertoire and the production of infectious virus in culture cells. Results described in this report constitute the first direct experimental evidence showing that birnaviral RNPs are intracellularly active in the absence of the virus capsid. This finding is consistent with presented data indicating that RNP formation precedes virus assembly in IBDV-infected cells, and supports the recently proposed IBDV replication model entailing the release of RNPs during the initial stages of the infection. Indeed, results presented here also support the previously proposed evolutionary connection between birnaviruses and positive-strand single-stranded RNA viruses.PLoS ONE 01/2014; 9(1):e87790. · 3.53 Impact Factor