Many of the rRNA base modification mutants have M₁ virus propagation defects.

<p>Yeast rRNA modification mutants were tested for their ability to maintain the L-A and M₁ viruses. (A) Mutant and isogenic wild-type yeast strains were spotted onto YPAD plates, and allowed to grow at 30°C, and then replica plated to a seeded lawn of 5X47 indicator cells. Plates were incubated at room temperature for 3–5 days until a zone of inhibition was clearly visible for wild-type cells. (B) Total RNAs were extracted from mutant and isogenic wild-type yeast strains and digested with RNase A under high salt conditions. The resulting double-stranded RNA was separated on a 1% agarose gel and visualized with ethidium bromide. L-A and M₁ dsRNAs are indicated. The image was inverted for clarity.