UNLEASHING CENTROMERIC EPIGENETICS IN BUDDING YEAST SACCHAROMYCES CEREVISIAE

Centromeric histone variant human CENP-A is frequently overexpressed and mislocalized in cancer cells, resulting in neocentromere formation, chromosome instability, and aneuploidy. In budding yeast, deletion of the E3 ubiquitin ligase, Psh1, reduces the turn-over rate of centromeric histone variant Cse4, the budding yeast homolog of CENP-A, and results in ectopic Cse4 loading. Little is known about the biophysical nature of the excess Cse4 and its effect on the spatiotemporal dynamics of kinetochore proteins. This study aims to further our knowledge of the phenotypical change of psh1Δ cells via super-resolution imaging. We discovered at least two of the kinetochore components in our study have transient and stable interactions at the centromere loci, with the majority of the population (~70%) being transient. Deletion of psh1 does not change the population distribution but results in an increase of detection levels of some kinetochore proteins at the centromere loci, such as Cse4, Mif2, Okp1, and Slk19. However, levels of Ndc10 and Cep3 are unchanged. The correlation between excess Cse4 around the centromere and the increase in some but not all kinetochore proteins demonstrates that kinetochore architecture is tightly regulated by both genetic and epigenetic mechanisms to control normal centromere function. The increase in some kinetochore proteins near endogenous centromere loci under these conditions also suggests a potential for ‘regional’ centromere assembly in Saccharomyces Cerevisiae