RNA-directed RNA polymerase that replicates the viral (+) and (-) genome. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Forms a ribonucleoprotein complex with the 20S RNA, where a single polymerase molecule binds to a single viral RNA genome. Since the viral RNA is not encapsidated, ribonucleoprotein complex formation appears to be the strategy to survive in the host as persistent virus. The virus has no extracellular transmission pathway. It exists as a ribonucleoprotein viral particle in the host cytoplasm and can be transmitted through mating or cytoplasmic mixing (cytoduction). Yeast strains also contain a double-stranded RNA (dsRNA) called W. The (+)-strand of W is identical to the single-stranded 20S RNA. The W dsRNA seems to be a by-product of the viral RNA replication cycle.