Models of how H3 and Cse4 can co-occupy the centromeric DNA.

<p>A heterotetramer of H3, H2A, H2B and H4 is colored in green and a heterotetramer containing Cse4 instead of H3 is blue.1) A heterotypic octamer containing both Cse4 and H3. 2) A heterotypic octamer with additional Cse4 bound to it. 3) A Cse4 hemisome incorporated in the loop of a conventional nucleosome. A DNA fragment of 207 bp is sufficient to accommodate this arrangement (without spacer DNA). 4) Two conventional nucleosomes flanking a Cse4 hemisome. The scissors indicate the BglII sites flanking the 214 bp fragment excised in our experiment. In case of model 4 this fragment would be tethered to non-centromeric DNA. The tethering was not observed in our experiments (<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1002739#pgen-1002739-g001" target="_blank">Figure 1C</a>). See text for discussion and additional details.