Identification of Saccharomyces cerevisiae ribosomal protein L3 as a target of curvularol, a G1-specific inhibitor of mammalian cells

The cellular target of curvularol, a G(1)-specific cell-cycle inhibitor of mammalian cells, was identified by a genetic approach in Saccharomyces cerevisiae. Since the wild-type W303 strain was highly resistant to curvularol, a drug hypersensitive parental strain was constructed in which various genes implicated in general drug resistance had been disrupted. Curvularol resistant mutants were isolated, and strains that exhibited a semi-dominant, curvularol-specific resistance phenotype were selected. All five strains examined were classified into a single genetic complementation group designated YCR1. A mutant gene responsible for curvularol resistance was identified as an allele of the RPL3 gene encoding the ribosomal protein L3. Sequence analysis of the mutant genes revealed that Trp255Cys and Trp255Leu substitutions of Rp13p are responsible for curvularol resistance. Rp13p mutants in which Trp255 residue was replaced by other amino acids were constructed. All of these replacements led to varying degrees of increased resistance to curvularol and growth defects.