A Candida albicans homolog of CDC25 is functional in Saccharomyces cerevisiae

We have cloned, by functional complementation of the cdc25‐2, mutation of Saccharomyces cerevisiae, a homolog of CDC25 from the pathogenic yeast Candida albicans. The new gene, named CSC25, codes for a 1333‐amino‐acid protein. The full length gene, as well as a truncated form coding for 795 amino acids, suppresses the thermosensitive phenotype of cdc25^ts mutants. Biochemical analysis has shown that Csc25 activates the Ras/adenylyl cyclase pathway in S. cerevisiae at a rate two to three times faster than Cdc25, under the same conditions. The C‐terminal domain of Csc25 is highly similar to the C‐terminal domain of Cdc25, to almost the same extent as the C‐terminus of the endogenous Cdc25 homolog Sdc25. We show that polyclonal anti‐Cdc25 antibodies interact with Csc25 expressed in S. cerevisiae. In addition to the full length protein (∼ 150 kDa), we have found a ∼ 50‐kDa polypeptide which seems to include the C‐terminus of the CSC25 gene product.