Histone H2A is required for normal centromere function in Saccharomyces cerevisiae

Histones are structural and functional components of the eukaryotic chromos ome, and their function is essential for normal cell cycle progression. In this work, we describe the characterization of two Saccharomyces cerevisiae cold-sensitive histone H2A mutants. Both mutants contain single amino acid replacements of residues predicted to be on the surface of the nucleosome and in close contact with DNA, We show that these H2A mutations cause an in crease-in-ploidy phenotype, an increased rate of chromosome loss, and a def ect in traversing the G(2)-M phase of the cell cycle. Moreover, these H2A m utations show genetic interactions with mutations in genes encoding kinetoc hore components. Finally, chromatin analysis of these H2A mutants has revea led an altered centromeric chromatin structure. Taken together, these resul ts strongly suggest that histone H2A is required for proper centromere-kine tochore function during chromosome segregation.