A 2ND DOUBLE-STRANDED-RNA VIRUS FROM YEAST

Two double-stranded RNA viruses exist as permanent persistent infectio ns of the yeast Saccharomyces cerevisiae: ScVL1 and ScVLa. Both belong to the Totiviridae, which include a number of fungal and protozoan do uble-stranded RNA viruses. Although ScVL1 and ScVLa share the same gen omic organization and mode of expression and coexist in the same cells , they show no evidence of recombination: with one limited exception, sequence conservation is detectable only in regions conserved in all t otiviruses. Both have two open reading frames on their single essentia l RNAs: cap (encoding a capsid polypeptide) and pol (encoding an RNA-d ependent RNA polymerase). The ScVLa virus, like ScVL1, appears to expr ess its Pol domain by a -1 translational frameshift. (C) 1996 Academic Press, Inc.