Effects of UV-irradiation upon Venezuelan equine encephalomyelitis virus.

Venezuelan equine encephalomyelitis virus labelled with [14C]aminoacids or [3H]uridine was purified and UV-irradiated. The irradiation led to the formation of uracil photodimers and the covalent linking of the nucleocapsid protein C to virion RNA. The inactivation of infectivity correlated with the formation of uracil dimers, whereas the RNA-protein links were formed at much higher doses of UV irradiation. The analysis of covalent RNA-protein complexes suggests that a fairly large fraction (at least one third) of the whole content of C protein is able to participate in the formation of UV-induced links, suggesting extensive contacts of RNA with protein with the nucleocapsid.