A novel small-molecule inhibitor of the chromosome segregation process in yeast

The centromeres of budding yeasts contain specific and essential DNA sequences, in contrast to the regional heterochromatic centromeres found in higher organisms. Small molecules that perturb centromere function in budding yeast could be valuable candidates for identifying yeast-specific growth inhibitors. A combination of two in vivo assays, one based on transcription blockade of a reporter gene by the centromeric DNA-protein complex, the other on a test for mitotic minichromosome stability, was used to identify small molecules that affect the process of chromosome segregation. One compound, here named incentrom A, leads to a minichromosome loss phenotype, and is cytotoxic to the budding yeast Saccharomyces cerevisiae. Furthermore, whereas cells carrying a conditional mutation in a gene for an essential kinetochore protein, skp1-4, are hypersensitive to incentrom A, cells that overexpress the SKP1 gene are resistant to the compound. Incentrom A also results in mitotic loss of a centromere-bearing plasmid, and inhibits the growth of the pathogenic yeast Candida glabrata. Incentrom A will therefore be a useful tool for studying the molecular basis of yeast chromosome segregation and could form the basis for the development of novel antifungal drugs.