RNA-dependent RNA polymerase activity in two morphologically different white clover cryptic viruses.

RNA-dependent RNA polymerase activities were detected in purified particles of white clover cryptic viruses 1 and 2. The polymerases of the two viruses had different requirements for optimum activity. Enzyme activity was dependent upon the presence of virus particles, Mg2+, and the four ribonucleoside triphosphates, and was insensitive to actinomycin D, alpha-amanitin, and rifampicin. The labeled reaction products were dsRNAs as indicated by CF 11 column chromatography and by their ionic-strength-dependent sensitivity to hydrolysis by RNase A and resistance to S1 nuclease. The dsRNAs synthesized in vitro had the same electrophoretic mobilities as the corresponding viral templates.