Oligomerization of the structural proteins of rubella virus.

Rubella virus contains, in addition to its RNA genome, a nucleocapsid protein (C) and two membrane proteins (E2 and E1). We have studied the association of these proteins during viral assembly and when expressed from cDNA constructs. The C protein was found to dimerize very shortly after synthesis; this dimer became disulfide-linked in the virion. Formation of the dimer was independent of the presence of other RV proteins. The membrane glycoproteins formed an E2E1 heterodimer, a minor fraction of which was also found to be disulfide-linked in the virion. This heterodimer also formed when the two proteins were coexpressed from cloned cDNA. Formation of the heterodimer preceded the transport of E2 to the Golgi, as judged by modification of the protein by Golgi-located enzymes. In the absence of E2, the E1 protein was slowly converted to high molecular weight aggregates.