Abstract
Messenger RNAs labelled in vivo in Vero cells infected with canine distemper virus were analysed by electrophoresis on 1.5% agarose gels containing 2M-formaldehyde. Seven virus-specific RNA bands could be distinguished which were not sensitive to actinomycin D treatment and were confined to the polyadenylated RNA fraction. The most abundant virus-specific mRNA species had a molecular weight of 0.52 x 106 and its coding capacity was consistent with it being the mRNA for the most abundant virus-specific protein, the nucleoprotein. Polyadenylated RNA of this size class was purified by electrophoresis on a polyacrylamide gel and cloned into the PstI site of plasmid pBR322. A virus-specific clone obtained, clone 224, was then used to select messenger RNA from infected cells. The messenger RNA selected had a molecular weight of 0.52 x 106 and directed the synthesis of only the virus-specific nucleoprotein when used to stimulate a wheat germ cell-free system.