A deletion mutant of L-A double-stranded RNA replicates like M1 double-stranded RNA.
X double-stranded RNA (dsRNA) is a 0.52-kilobase dsRNA molecule that arose spontaneously in a nonkiller strain of Saccharomyces cerevisiae originally containing L-A and L-BC dsRNAs (L-BC is the same size as L-A but shares no homology with it). X hybridized with L-A, and direct RNA sequencing of X showed that the first 5' 25 base pairs (of the X positive strand) and at least the last 110 base pairs of the 3' end were identical to the ends of L-A dsRNA. X showed cytoplasmic inheritance and, like M1, was dependent on L-A for its maintenance. X was encapsidated in viruslike particles whose major coat protein was provided by L-A (as is true for M1), and X was found in viruslike particles with one to eight X molecules per particle. This finding confirms our "head-full replication" model originally proposed for M1 and M2. Like M1 or M2, X lowers the copy number of L-A, especially in a ski host. Surprisingly, X requires many chromosomal MAK genes that are necessary for M1 but not for L-A.
Esteban
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R
Section on Genetics of Simple Eukaryotes, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
Wickner
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RB
D001483:Base Sequence; D004587:Electrophoresis, Agar Gel; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D009154:Mutation; D009693:Nucleic Acid Hybridization; D012330:RNA, Double-Stranded / Q000096:biosynthesis / Q000235:genetics*; D012331:RNA, Fungal / Q000096:biosynthesis / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism
D012330:RNA, Double-Stranded; D012331:RNA, Fungal