Elimination of L-A double-stranded RNA viruses of Saccharomyces cerevisiae by expression of gag and gag-pol from an L-A cDNA clone
1993
Valle, R.P.C. | Wickner, R.B.
We report that expression of a nearly full-length cDNA clone of the L-A double-stranded RNA virus causes virus loss in a wild-type strain of Saccharomyces cerevisiae. We show that in this system exclusion of the L-A virus is independent of the presence of the packaging site or of cis sites for replication and transcription and completely dependent on expression of functional recombinant gag and gag-pol fusion protein. Thus, this exclusion is not explained in terms of overexpression or packaging signals. Mutation of the chromosomal SKI2 gene, known to repress the copy number of double-stranded RNA cytoplasmic replicons of S. cerevisiae, nearly eliminates the exclusion. We suggest that exclusion is due to competition by proteins expressed from the plasmid for a possibly limiting cellular factor. Our hypotheses on exclusion by expression of L-A proteins may also apply to resistance to plant viruses produced by expression of viral replicases in transgenic plants.
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