During cell division, segregation of sister chromatids to daughter cells is 
achieved by the poleward pulling force of microtubules, which attach to the 
chromatids by means of a multiprotein complex, the kinetochore. Kinetochores 
assemble at the centromeric DNA organized by specialized centromeric 
nucleosomes. In contrast to other eukaryotes, which typically have large 
repetitive centromeric regions, budding yeast CEN DNA is defined by a 125 bp 
sequence and assembles a single centromeric nucleosome. In budding yeast, as 
well as in other eukaryotes, the Cse4 histone variant (known in vertebrates as 
CENP-A) is believed to substitute for histone H3 at the centromeric nucleosome. 
However, the exact composition of the CEN nucleosome remains a subject of 
debate. We report the use of a novel ChIP approach to reveal the composition of 
the centromeric nucleosome and its localization on CEN DNA in budding yeast. 
Surprisingly, we observed a strong interaction of H3, as well as Cse4, H4, H2A, 
and H2B, but not histone chaperone Scm3 (HJURP in human) with the centromeric 
DNA. H3 localizes to centromeric DNA at all stages of the cell cycle. Using a 
sequential ChIP approach, we could demonstrate the co-occupancy of H3 and Cse4 
at the CEN DNA. Our results favor a H3-Cse4 heterotypic octamer at the budding 
yeast centromere. Whether or not our model is correct, any future model will 
have to account for the stable association of histone H3 with the centromeric 
DNA.