The internal polyadenylate tract of yeast killer virus M1 double-stranded RNA is variable in length.

The 1.8-kbp M1 double-stranded (ds) RNA from type 1 killer strains of Saccharomyces cerevisiae contains an internal 200-bp adenine- and uracil-rich region. We have previously demonstrated that this region consists primarily of adenine residues on the plus strand of M1 dsRNA and on the full-length, in vitro synthesized (+) transcript (denoted m) of M1 dsRNA, neither of which contains 3'-terminal polyadenylate. We now show that there is variability in the length of the polyadenylate tracts of m transcripts synthesized in vitro by virions purified from either of the K1 diploid killer strains A364A X S7 or A364A X 1384. This variability reflects size differences seen in the corresponding M1 dsRNA genomes which, along with other data presented, localizes the variability in the length of M1 dsRNA to the adenine- and uracil-rich region.