Deposition of Centromeric Histone H3 Variant CENP-A/Cse4 into Chromatin Is Facilitated by Its C-Terminal Sumoylation

Centromeric localization of CENP-A ( in Saccharomyces cerevisiae, CID in flies, CENP-A in humans) is essential for faithful chromosome segregation. Mislocalization of overexpressed CENP-A contributes to aneuploidy in yeast, flies, and humans, and is proposed to promote tumorigenesis in human cancers. Hence, defining molecular mechanisms that promote or prevent mislocalization of CENP-A is an area of active investigation. In budding yeast, evolutionarily conserved histone chaperones and chromatin assembly factor-1 (CAF-1) promote localization of to centromeric and noncentromeric regions, respectively. Ubiquitin ligases, such as and , and histone chaperones (HIR complex) regulate proteolysis of overexpressed and prevent its mislocalization to noncentromeric regions. In this study, we have identified sumoylation sites lysine (K) 215/216 in the C terminus of , and shown that sumoylation of K215/216 facilitates its genome-wide deposition into chromatin when overexpressed. Our results showed reduced levels of sumoylation of mutant K215/216R/A [K changed to arginine (R) or alanine (A)] and reduced interaction of mutant K215/216R/A with and CAF-1 when compared to wild-type . Consistent with these results, levels of K215/216R/A in the chromatin fraction and localization to centromeric and noncentromeric regions were reduced. Furthermore, in contrast to GAL-, which exhibits Synthetic Dosage Lethality (SDL) in increment , increment , and increment strains, GAL- K215/216R does not exhibit SDL in these strains. Taken together, our results show that deposition of into chromatin is facilitated by its C-terminal sumoylation.