CANDIDA-ALBICANS SSD1 CAN SUPPRESS MULTIPLE MUTATIONS IN SACCHAROMYCES-CEREVISIAE

The SSD1 gene of Saccharomyces encodes a 160 kDa cytoplasmic protein t hat can suppress mutations in a number of other genes. A functional ho mologue of SSD1 from the human pathogen Candida albicans was isolated on the basis of its ability to restore viability at the restrictive te mperature in a Saccharomyces cerevisiae swi4 ssd1-d strain. The C. alb icans gene, designated CaSSD1, encodes a 1262 aa protein which has 47% identity overall to S. cerevisiae SSD1 as well as significant identit y to Schizosaccharomyces pombe dis3 and sts5 products. It is shown tha t CaSSD1 expression is constitutive through the mitotic cell cycle, wh ich is consistent with a role for the protein in cell growth. CaSSD1 r escues the swi4(ts) defect in an ssd1-d background when expressed from its own promoter on a single-copy plasmid and under the same conditio ns can rescue mutations in genes encoding protein phosphatase type 2A catalytic subunits. These data suggest that CaSSD1, like its S. cerevi siae homologue. can limit the effect of mutations on a variety of cell ular processes.