The cloning and characterization of the CDC50 gene family in Saccharomyces cerevisiae

We have cloned a gene that complements the cold-sensitive growth of cdc50-1 mutant strain of Saccharomyces cerevisiae at 14°C. The CDC50 gene was found to be identical to YCR094w on chromosome III and contains 1173 nucleotides encoding 391 amino acids. We found a missense mutation at the first initiation codon of cdc50-1. The disruption of the CDC50 gene revealed that it is not essential for growth, but the disruptant caused the same cold-sensitive phenotype as cdc50-1, suggesting that the cdc50-1 is a null mutation resulted from the mutation in the first codon. The cdc50-1 mutant arrests at START in G₁ phase at the non-permissive temperature. The CDC50 gene product has strong structural similarity to two other proteins in Saccharomyces cerevisiae encoded by YNR048w and YNL323w. The over-expression of either YNR048w or YNL323w suppressed the cdc50-1 mutant and the double disruption of either CDC50 and YNR048w or CDC50 and YNL323w resulted in a severe slow-growth phenotype. We conclude that these three genes constitute a family with redundant function. We also found that the CDC39 gene was a multicopy suppressor of cdc50-1 mutation, suggesting that the CDC50 family is involved in regulation of transcription via CDC39.