title: Pairs of Vp1 cysteine residues essential for simian virus 40 infection.
abstract: Transient disulfide bonding occurs during the intracellular folding and pentamerization of simian virus 40 (SV40) major capsid protein Vp1 (P. P. Li, A. Nakanishi, S. W. Clark, and H. Kasamatsu, Proc. Natl. Acad. Sci. USA 99:1353-1358, 2002). We investigated the requirement for Vp1 cysteine pairs during SV40 infection. Our analysis identified three Vp1 double-cysteine mutant combinations that abolished viability as assayed by plaque formation. Mutating the Cys49-Cys87 pair or the Cys87-Cys254 pair led to ineffective nuclear localization and diminished accumulation of the mutant Vp1s, and the defect extended in a dominant-negative manner to the wild-type minor capsid proteins Vp2/3 and an affinity-tagged recombinant Vp1 expressed in the same cells. Mutating the Cys87-Cys207 pair preserved the nuclear localization and normal accumulation of the capsid proteins but diminished the production of virus-like particles. Our results are consistent with a role for Cys49, Cys87, and Cys254 in the folding and cytoplasmic-nuclear trafficking of Vp1 and with a role for Cys87 and Cys207 in the assembly of infectious particles. These findings suggest that transient disulfide bond formation between certain Vp1 cysteine residues functions at two stages of SV40 infection: during Vp1 folding and oligomerization in the cytoplasm and during virion assembly in the nucleus.
authors.affiliation: Molecular Biology Institute, 456 Boyer Hall, University of California at Los Angeles, 611 East Charles E. Young Dr., Box 951570, Los Angeles, CA 90095-1570, USA.
authors.forename: Peggy P
authors.initials: PP
authors.lastname: Li
authors.forename: Akira
authors.initials: A
authors.lastname: Nakanishi
authors.forename: Vanessa
authors.initials: V
authors.lastname: Fontanes
authors.forename: Harumi
authors.initials: H
authors.lastname: Kasamatsu
mesh_terms: D019943:Amino Acid Substitution; D036022:Capsid Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D002467:Cell Nucleus / Q000737:chemistry; D003545:Cysteine / Q000235:genetics* / Q000502:physiology*; D009154:Mutation; D021381:Protein Transport; D013539:Simian virus 40 / Q000254:growth & development / Q000502:physiology*; D010948:Viral Plaque Assay; D019065:Virus Assembly; D014779:Virus Replication
chemical_list: D036022:Capsid Proteins; C062481:VP1 protein, polyomavirus; C085902:VP3 protein, Simian virus 40; D003545:Cysteine
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