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 degrees 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.