An E3 Ubiquitin Ligase Prevents Ectopic Localization of the Centromeric Histone H3 Variant via the Centromere Targeting Domain

Proper centromere function is critical to maintain genomic stability and to prevent aneuploidy, a hallmark of tumors and birth defects. A conserved feature of all eukaryotic centromeres is an essential histone H3 variant called CENP-A that requires a centromere targeting domain (CATD) for its localization. Although proteolysis prevents CENP-A from mislocalizing to euchromatin, regulatory factors have not been identified. Here, we identify an E3 ubiquitin ligase called Psh1 that leads to the degradation of Cse4, the budding yeast CENP-A homolog. Cse4 overexpression is toxic to psh1Δ cells and results in euchromatic localization. Strikingly, the Cse4 CATD is a key regulator of its stability and helps Psh1 discriminate Cse4 from histone H3. Taken together, we propose that the CATD has a previously unknown role in maintaining the exclusive localization of Cse4 by preventing its mislocalization to euchromatin via Psh1-mediated degradation. ► Psh1 is an E3 ubiquitin ligase that recognizes the Cse4 centromeric histone variant ► Psh1-mediated degradation prevents the ectopic localization of Cse4 ► Psh1 recognizes Cse4 via the centromere targeting domain