CSE4P IS A COMPONENT OF THE CORE CENTROMERE OF SACCHAROMYCES-CEREVISIAE

Histones are fundamental structural components of chromatin and are ex pected to play important roles in chromosome dynamics. Here, we presen t direct evidence that Cse4p, a histone H3 variant, is a structural co mponent of the core centromere of S. cerevisiae. In histone H4 and Cse 4p mutants, the core centromere chromatin structure is disrupted at re strictive temperature. Overexpression of Cse4p suppresses this defect in the H4 mutant, implying that the two proteins act together in centr omere structure. We show by chromatin immunoprecipitation experiments that Cse4p is specifically cross-linked to centromeric DNA. Furthermor e, by immunofluorescence microscopy, Cse4p is found in discrete foci c onsistent with that expected for centromeres. These results suggest th e kinetochore is assembled on a specialized centromeric nucleosome con taining Cse4p.