THE MODE OF INHIBITION OF TMV-INDUCED AND PVX-INDUCED RNA-DEPENDENT RNA-POLYMERASES BY SOME ANTIPHYTOVIRAL DRUGS

Six nucleobase and nucleoside analogues (6-aminouracil [6-AU], 6-amino thymin [6-AT], 6-fluorothymin [6-FT], 2,4-dioxohexahydro-1,3,5-triazin e [DHT], 9-(2,3-dihydroxypropyl)adenine [DHPA] and 1-beta-D-ribofurano syl-1,2,4-triazol-3-carboxamid [ribavirin]) with potential antiphytovi ral activity were tested in an in vitro replication system for their e ffect on tobacco mosaic virus (TMV)- and potato virus X(PVX)-induced R NA dependent RNA polymerase. 6-AU, 6-AT, 6-FT, and DHPA inhibited both polymerases which may be a target of these compounds. A putative non- competitive mode of inhibition is discussed. Whereas ribavirin did not affect the in vitro RNA synthesis in the established systems, the ura cil-derivative DHT inhibited only the PVX-specific enzyme.