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Genetic analysis of maintenance and expression of L and M double‐stranded RNAs from yeast killer virus K 28
Author(s) -
Schmitt Manfred J.,
Tipper Donald J.
Publication year - 1992
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/yea.320080505
Subject(s) - biology , rna silencing , saccharomyces cerevisiae , phenotype , microbiology and biotechnology , capsid , virus , viral replication , yeast , clone (java method) , strain (injury) , rna , virology , genetics , rna interference , gene , anatomy
The killer phenotype expressed by Saccharomyces cerevisiae strain 28 differs fron that of the more extensively studied K 1 and K 2 killers with respect to immunity, mode of toxin action and cell wall primary toxin receptor. We previosly demonstrated that the M 28 and L 28 dsRNAs found in strain 28 are present in virus‐like particles (VLPs) and that transfection with these VLPs is sufficient to confer the complete K 28 phenotype on a dsRNA‐free recipient cell. We also demonstrated that L 28 , like the L‐A‐H species in K 1 killers, has [HOK] activity required for maintenance of M 1 ‐dsRNA, and predicted that M 28 would share with M 1 dependence on L‐A for replication. We now confirm this prediction by genetic and biochemical analysis of the effects of representative mak , ski and mkt mutations on M 28 maintenance, demonstrating that M 28 replication resebles M 1 in all respects. We also show that L 28 is an L‐A‐H species lacking [B] activity, and that M 28 excludes both M 1 and M 2 from the same cytoplasm. Stable coexpression of K 28 phenotype from M 28 and of K 1 phenotype from an M 1 ‐cDNA clone was demonstrated. Exclusion, therefore, acts at the level of dsRNA replication, presumably reflecting competition for the L‐A‐H encoded capsid and cap‐pol fusion protein, rather than reflecting incompatibility of toxin or immunity expression. Finally, we show that expression of active K 28 toxin, bu t not of K 28 immunity, requires the Kex2 endoprotease.