title: Conserved serines in simian immunodeficiency virus capsid are required for virus budding.
abstract: The simian immunodeficiency virus (SIV) capsid protein (CA), a constituent of the Pr55Gag polyprotein, is phosphorylated in virions but not in virus-producing cells (Rue, S.M., Roos, J.W., Tarwater, P.M., Clements, J.E., Barber, S.A., 2005. Phosphorylation and proteolytic cleavage of gag proteins in budded simian immunodeficiency virus. J. Virol. 79 (4), 2484-2492.). Using phosphoamino acid analysis of CA, we show that serine is the primary phosphate acceptor. A series of substitution mutants of serines in the CA domain of Pr55Gag were constructed in the infectious viral clone SIVmac239. These virus mutants were examined for defects in virus replication and virion infectivity, release, and morphology, as well as alterations in phosphorylation of CA-containing proteins. Although the virus mutants exhibited a number of replication defects, none of these defects could be directly attributed to aberrant CA phosphorylation. A novel defect was a block in early budding, which was common among several virus mutants with substitutions in the CA N terminus. Together, these results indicate that certain residues in the CA N terminus are crucial for early budding events.
authors.affiliation: Department of Comparative Medicine, Johns Hopkins University School of Medicine, 733 N. Broadway, Room 831, Baltimore, MD 21205, USA.
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Rue
authors.forename: Jason W
authors.initials: JW
authors.lastname: Roos
authors.forename: Janice E
authors.initials: JE
authors.lastname: Clements
authors.forename: Sheila A
authors.initials: SA
authors.lastname: Barber
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D036022:Capsid Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D017124:Conserved Sequence / Q000502:physiology*; D017930:Genes, Reporter; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D012194:RNA-Directed DNA Polymerase / Q000032:analysis; D012694:Serine / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D015302:Simian Immunodeficiency Virus / Q000235:genetics / Q000254:growth & development* / Q000648:ultrastructure; D014779:Virus Replication
chemical_list: D036022:Capsid Proteins; D012694:Serine; D008156:Luciferases; D012194:RNA-Directed DNA Polymerase