Centromere-Like Regions in the Budding Yeast Genome

Accurate chromosome segregation requires centromeres ( CEN s), the DNA sequences where kinetochores form, to attach chromosomes to microtubules. In contrast to most eukaryotes, which have broad centromeres, Saccharomyces cerevisiae possesses sequence-defined point CEN s. Chromatin immunoprecipitation followed by sequencing (ChIP–Seq) reveals colocalization of four kinetochore proteins at novel, discrete, non-centromeric regions, especially when levels of the centromeric histone H3 variant, Cse4 (a.k.a. CENP-A or CenH3), are elevated. These regions of overlapping protein binding enhance the segregation of plasmids and chromosomes and have thus been termed Centromere-Like Regions ( CLR s). CLR s form in close proximity to S. cerevisiae CEN s and share characteristics typical of both point and regional CEN s. CLR sequences are conserved among related budding yeasts. Many genomic features characteristic of CLR s are also associated with these conserved homologous sequences from closely related budding yeasts. These studies provide general and important insights into the origin and evolution of centromeres.