TRANSLATION AND M(1) DOUBLE-STRANDED-RNA PROPAGATION - MAK18=RPL41B AND CYCLOHEXIMIDE CURING

MAK18 is one of nearly 30 chromosomal genes of Saccharomyces cerevisia e necessary for propagation of the killer toxin-encoding M(1) double-s tranded RNA satellite of the L-A double-stranded RNA virus. We have cl oned and sequenced MGK18 and find that it is identical to RPL41B, one of the two genes encoding large ribosomal subunit protein L41. The mak 18-1 mutant is deficient in 60S subunits, which we suggest results in a preferential decrease in translation of viral poly(A)-deficient mRNA . We have reexamined the curing of M, by low concentrations of cyclohe ximide (G. R. Fink and C. A. Styles, Proc. Natl. Acad. Sci. USA 69:284 6-2849, 1972), which is known to act on ribosomal large subunit protei n L29. We find that when M(1) is supported by L-A proteins made from t he poly(A)(+) mRNA of a cDNA clone of L-A, cycloheximide does not decr ease the M(1) copy number, consistent with our hypothesis.