Multiple E3s promote the degradation of histone H3 variant Cse4.

The histone H3-like protein Cse4/CENP-A acts as a key molecular marker that differentiates the special centromeric chromatin structures from bulk nucleosomes. As altered Cse4/CENP-A activity leads to genome instability, it is pivotal to understand the mechanism underlying Cse4 regulation. Here, we demonstrate that four ubiquitin ligases (i.e., Ubr1, Slx5, Psh1, and Rcy1) work in parallel to promote Cse4 turnover in yeast. Interestingly, Cse4 overexpression leads to cellular toxicity and cell cycle delay in yeast cells lacking PSH1, but not in cells lacking UBR1, suggesting different roles of these two degradation pathways. Our findings suggest that various ubiquitin ligases collaborate to keep the Cse4 level in check, providing a basis for further delineating the intricate network involved in Cse4 regulation.