EVIDENCE THAT THE MIF2 GENE OF SACCHAROMYCES-CEREVISIAE ENCODES A CENTROMERE PROTEIN WITH HOMOLOGY TO THE MAMMALIAN CENTROMERE PROTEIN CENP-C

The MIF2 gene of Saccharomyces cerevisiae has been implicated in mitos is. Here we provide genetic evidence that MIF2 encodes a centromere pr otein. Specifically, we found that mutations in MIF2 stabilize dicentr ic minichromosomes and confer high instability (i.e., a synthetic acen tric phenotype) to chromosomes that bear a cis-acting mutation in elem ent I of the yeast centromeric DNA (CDEI). Similarly, we observed synt hetic phenotypes between mutations in MIF2 and trans-acting mutations in three known yeast centromere protein genes-CEP1/CBF1/CPF1, NDC10/CB F2, and CEP3/CBF3B. In addition, the mif2 temperature-sensitive phenot ype can be partially rescued by increased dosage of CEP1. Synthetic le thal interactions between a cep1 null mutation and mutations in either NDC10 or CEP3 were also detected. Taken together, these data suggest that the. Mif2 protein interacts with Cep1p at the centromere and that the yeast centromere indeed exists as a higher order protein-DNA comp lex. The Mif2 and Cep1 proteins contain motifs of known transcription factors, suggesting that assembly of the yeast centromere is analogous to that of eukaryotic enhancers and origins of replication. We also s how that the predicted Mif2 protein shares two short regions of homolo gy with the mammalian centromere Ag CENP-C and that two temperature-se nsitive mutations in MIF2 lie within these regions. These results prov ide evidence for structural conservation between yeast and mammalian c entromeres.