A Genome-Wide Screen Reveals a Role for the HIR Histone Chaperone Complex in Preventing Mislocalization of Budding Yeast CENP-A.
Genetics. 2018 Jul 16;:
Authors: Ciftci-Yilmaz S, Au WC, Mishra PK, Eisenstatt JR, Chang J, Dawson AR, Zhu I, Rahman M, Bilke S, Costanzo M, Baryshnikova A, Myers CL, Meltzer PS, Landsman D, Baker RE, Boone C, Basrai MA
Centromeric localization of the evolutionarily conserved centromere-specific histone H3 variant CENP-A (Cse4 in yeast) is essential for faithful chromosome segregation. Overexpression and mislocalization of CENP-A leads to chromosome segregation defects in yeast, flies, and human cells. Overexpression of CENP-A has been observed in human cancers; however, the molecular mechanisms preventing CENP-A mislocalization are not fully understood. Here, we used a genome-wide Synthetic Genetic Array (SGA) to identify gene deletions that exhibit synthetic dosage lethality (SDL) when Cse4 is overexpressed. Deletion for genes encoding the replication-independent histone chaperone HIR complex (HIR1, HIR2, HIR3, HPC2) and a Cse4-specific E3 ubiquitin ligase, PSH1, showed highest SDL. We defined a role for Hir2 in proteolysis of Cse4 that prevents mislocalization of Cse4 to non-centromeric regions for genome stability. Hir2 interacts with Cse4 invivo and hir2Δ strains exhibit defects in Cse4 proteolysis, and stabilization of chromatin-bound Cse4. Mislocalization of Cse4 to non-centromeric regions with a preferential enrichment at promoter regions was observed in hir2Δ strains. We determined that Hir2 facilitates the interaction of Cse4 with Psh1 and that defects in Psh1-mediated proteolysis contribute to increased Cse4 stability and mislocalization of Cse4 in the hir2Δ strain. In summary, our genome-wide screen provides insights into pathways that regulate proteolysis of Cse4 and defines a novel role for the HIR complex in preventing mislocalization of Cse4 by facilitating proteolysis of Cse4 thereby promoting genome stability.
PMID: 30012561 [PubMed - as supplied by publisher]