Protein Products of the Open Reading Frames Encoding Nonstructural Proteins of Human Astrovirus Serotype 8

Méndez, Ernesto; Salas-Ocampo, M. P. Elizabeth; Munguı́a, Maria Elena; Arias, Carlos F.

doi:10.1128/jvi.77.21.11378-11384.2003

Cited by 46 publications

(53 citation statements)

References 26 publications

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“…Our findings indicate that the C-terminal end of nsP1a must be further processed. With antibodies directed against a broader region of the nsP1a C terminus in a transient expression system on BHK-21 cells, other authors detected a 20-kDa protein, which was not observed with CaCo-2-infected cells at 12 h postinfection, probably due to further proteolytic processing of the protein (36). In addition, with similar approaches and longer incubation times, Willcocks et al reported proteins of 34, 20, 6.5, and 5.5 kDa (60).…”

Section: Discussionmentioning

confidence: 99%

“…A Ϸ27-kDa protein containing the protease motif would be generated by cleavage at residues Val 409 and Glu 654 (11). The cleavage site reported by Kiang and Matsui (30) at Gln 567 of nsP1a, which would produce two proteins of Ϸ64 and Ϸ38 kDa, does not seem to occur in HAstV-8-infected cells (36), but it is unclear whether it could be functional in other HAstV strains. With antibodies against approximately 30% of the nsP1a C-terminal region, different authors identified products of 34, 20, 6.5, and 5.5 kDa, but no other cleavage sites were suggested (36,60).…”

mentioning

confidence: 99%

“…Data about HAstV nonstructural polyprotein processing are still controversial; at least four cleavage sites have been suggested within nsP1a, and it is assumed that both viral and cellular proteases are responsible for the process (11,12,24,36,60). Processing at the amino terminus of nsP1a and nsP1a/1b is likely to occur cotranslationally, probably at residue Ala 174 , giving rise to a Ϸ20-kDa N-terminal product (36).…”

mentioning

confidence: 99%

“…Processing at the amino terminus of nsP1a and nsP1a/1b is likely to occur cotranslationally, probably at residue Ala 174 , giving rise to a Ϸ20-kDa N-terminal product (36). A Ϸ27-kDa protein containing the protease motif would be generated by cleavage at residues Val 409 and Glu 654 (11).…”

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confidence: 99%

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C-Terminal nsP1a Protein of Human Astrovirus Colocalizes with the Endoplasmic Reticulum and Viral RNA

Guix

Caballero

Bosch

et al. 2004

J Virol

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Computational and biological approaches were undertaken to characterize the role of the human astrovirus nonstructural protein nsP1a/4, located at the C-terminal fragment of nsP1a. Computer analysis reveals sequence similarities to other nonstructural viral proteins involved in RNA replication and/or transcription and allows the identification of a glutamine-and proline-rich region, the prediction of many phosphorylation and O-glycosylation sites, and the occurrence of a KKXX-like endoplasmic reticulum retention signal. Immunoprecipitation analysis with an antibody against a synthetic peptide of the nsP1a/4 sequence detected polyprotein precursors of 160, 75, and 38 to 40 kDa as well as five smaller proteins in the range of 21 to 27 kDa. Immunofluorescence labeling showed that the nsP1a/4 protein is accumulated at the perinuclear region, in association with the endoplasmic reticulum and the viral RNA. These results suggest the involvement of nsP1a/4 protein in the RNA replication process in endoplasmic reticulum-derived intracellular membranes.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

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C-Terminal nsP1a Protein of Human Astrovirus Colocalizes with the Endoplasmic Reticulum and Viral RNA

Guix

Caballero

Bosch

et al. 2004

J Virol

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“…The nsp1ab protein is produced from both ORF1a and ORF1b through a translational frame-shift mechanism (3). Polyproteins nsp1a and nsp1ab are processed by a viral 3C-like serine protease and other cellular proteases into several proteins (e.g., the RNAdependent RNA polymerase and the serine protease) that are likely to function in the replication of the viral genome (4). ORF2 at the 3′ end of the viral genome encodes the viral capsid protein (CP) (5) and is found in both genomic and subgenomic RNAs.…”

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Crystal structure of the human astrovirus capsid spike

Dong

Méndez

et al. 2011

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

118

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Astroviruses are single-stranded, plus-sense RNA viruses that infect both mammals and birds, causing gastroenteritis and other extraintestinal diseases. Clinical studies have established astroviruses as the second leading cause of viral diarrhea in young children. Here we report the crystal structure of the human astrovirus dimeric surface spike determined to 1.8-Å resolution. The overall structure of each spike/projection domain has a unique three-layered β-sandwiches fold, with a core, six-stranded β-barrel structure that is also found in the hepatitis E virus capsid protrusions, suggesting a closer phylogenetic relationship between these two viruses than previously acknowledged. Based on a hepatitis E virus capsid model, we performed homology modeling and produced a complete, T ¼ 3 astrovirus capsid model with features remarkably similar to those observed in a cryoelectron microscopy reconstruction image of a human astrovirus. Mapping conserved residues onto the astrovirus projection domain revealed a putative receptor binding site with amino acid compositions characteristic for polysaccharide recognition. Our results will have an important impact on future characterization of astrovirus structure and function, and will likely have practical applications in the development of vaccines and antivirals.structural protein | naked virus | attachment domain A stroviruses are small, nonenveloped, icosahedral viruses with a positive-sense, single-stranded RNA genome of approximately 7 kb in size. With members infecting mammals and avian species, the family of Astroviridae consists of two genera, Mammastrovirus and Avastrovirus (1, 2). Human astroviruses, eight serotypes in total, are one of the leading causes of gastroenteritis in young children, elderly people, and immunocompromised adults. Sporadic astrovirus infections as well as large-scale outbreaks in susceptible populations have been described (2). In addition to humans, astroviruses can infect a wide range of wild and domestic animals, causing gastroenteritis in most mammals and both intestinal and extraintestinal diseases in birds (1).The genomic RNA of astroviruses is polyadenylated with three ORFs. ORF1a and the downstream overlapping ORF1b encode two nonstructural polyproteins, nsp1a and nsp1ab. The nsp1ab protein is produced from both ORF1a and ORF1b through a translational frame-shift mechanism (3). Polyproteins nsp1a and nsp1ab are processed by a viral 3C-like serine protease and other cellular proteases into several proteins (e.g., the RNAdependent RNA polymerase and the serine protease) that are likely to function in the replication of the viral genome (4). ORF2 at the 3′ end of the viral genome encodes the viral capsid protein (CP) (5) and is found in both genomic and subgenomic RNAs. It is unclear whether the astrovirus RNA contains a 5′ cap. Viral capping enzymes such as guanylyltranferase and methyltransferases have not been identified in the astrovirus genome.When overexpressed in eukaryotic hosts, the 796-aa CP of the serotype 2 astrovirus was ...

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Genetic analysis of the hypervariable region of the human astrovirus nsp1a coding region: Design of a new RFLP typing method

Guix

Caballero

Fuentes

et al. 2007

Journal of Medical Virology

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Human astroviruses (HAstV) are causative agents of viral gastroenteritis worldwide. A hypervariable region (HVR) is located close to the C-terminus of the nsP1a, and recent data support the involvement of the HVR-containing nonstructural protein in viral RNA replication processes, suggesting a correlation between variability in this region and pathogenic properties. The HVR of the C-terminal nsP1a coding region of 104 wild-type and reference isolates of HAstV was sequenced. A phylogenetic analysis was performed to identify different genotypes, and a restriction fragment length polymorphism (RFLP) method was designed. An extensive nucleotide and deduced amino acid sequence variability was observed, as well as many insertions and deletions that retained the reading frame. The resultant phylogenetic tree supported the subdivision of HAstV into the two previously described major genetic groups, genogroup A and B, and the identification of 12 genotypes (9 within genogroup A, and 3 within genogroup B), which could be identified by RFLP. A correlation analysis was performed between genotype information and viral load using information from 35 clinical samples. Significant differences were observed between the viral load in clinical samples and certain HAstV genotypes that belonged to the same serotype, confirming the influence of C-terminal nsP1a variability on the viral replication phenotype. The use of the new RFLP typing method based on the HVR of the C-terminal nsP1a coding region by diagnosticians would help to understand the relationship between different genotypes and the severity of the gastroenteritis.

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Protein Products of the Open Reading Frames Encoding Nonstructural Proteins of Human Astrovirus Serotype 8

Cited by 46 publications

References 26 publications

C-Terminal nsP1a Protein of Human Astrovirus Colocalizes with the Endoplasmic Reticulum and Viral RNA

C-Terminal nsP1a Protein of Human Astrovirus Colocalizes with the Endoplasmic Reticulum and Viral RNA

Crystal structure of the human astrovirus capsid spike

Genetic analysis of the hypervariable region of the human astrovirus nsp1a coding region: Design of a new RFLP typing method

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