Conserved serines in simian immunodeficiency virus capsid are required for virus budding

• Published in: Virology (New York, N.Y.) Vol. 336; no. 1; pp. 37 - 50
• Main Authors: Rue, Sarah M., Roos, Jason W., Clements, Janice E., Barber, Sheila A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 25-05-2005
• Subjects: Amino Acid Sequence; Amino Acid Substitution; Budding; Capsid; Capsid Proteins - chemistry; Capsid Proteins - genetics; Capsid Proteins - physiology; Conserved Sequence - physiology; Gag; Genes, Reporter; Luciferases - genetics; Luciferases - metabolism; Molecular Sequence Data; Mutagenesis, Site-Directed; Phosphorylation; RNA-Directed DNA Polymerase - analysis; Serine; Serine - chemistry; Serine - genetics; Serine - physiology; Simian immunodeficiency virus; Simian Immunodeficiency Virus - genetics; Simian Immunodeficiency Virus - growth & development; Simian Immunodeficiency Virus - ultrastructure; SIV; Virus Replication; SIV; Phosphorylation; Capsid; Gag; Budding; Serine
• ISSN: 0042-6822; 1096-0341
• DOI: 10.1016/j.virol.2005.03.006

The simian immunodeficiency virus (SIV) capsid protein (CA), a constituent of the Pr55
Gag 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 Pr55
Gag 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.