Dimerization of rubella virus capsid protein is not required for virus particle formation

Rubella virus (RV) virions contain, in addition to the RNA genome, a capsid protein (C) and two envelope glycoproteins (E1 and E2). The C protein in isolated virions has been reported to be a disulfide-linked dimer (C2). There are two cysteine residues (Cys-152 and Cys-196) within the C protein. To define the role of disulfide-linked C2 dimer in virion formation, site-directed mutagenesis was used to alter the Cys-152 residue to serine. The association of mutant C protein with envelope glycoproteins was examined by transient expression of the cDNAs in COS cells. Mutation at the Cys-152 residue completely abolished the formation of C2 dimer. However, C2 dimerization does not appear to be important for the assembly of RV structural proteins into virus-like particles.