Functional characterization of CaCBF1, the Candida albicans homolog of centromere binding factor 1

The centromere binding factor 1 (Cbf1) is necessary for proper chromosome segregation and transcriptional activation of methionine biosynthesis genes in the yeast Saccharomyces cerevisiae and is essential for viability in the related yeasts Kluyveromyces lactis and Candida glabrata. To study the function of Cbf1p in Candida albicans, the major human fungal pathogen, we constructed strains in which both alleles of the CaCBF1 gene were deleted. The Deltacbf1 mutants exhibited a slow growth phenotype and were temperature-sensitive at 42 degrees C. In addition, the mutants were auxotrophic for sulfur amino acids and could grow on minimal medium only when it was supplemented with either methionine or cysteine, suggesting that CaCBF1 is necessary for the expression of genes involved in assimilation of inorganic sulfate. Deletion of CaCBF1 also resulted in morphological abnormalities, many cells being unusually large. All mutant phenotypes were complemented by reintroduction of a functional CaCBF1 copy. The Deltacbf1 mutants neither showed enhanced sensitivity to the microtubule destabilizing agent thiabendazole nor did they exhibit an increased frequency of chromosome loss. These results suggest that Cbf1p is not necessary for efficient chromosome segregation in C. albicans.