Dbf4-Dependent Kinase (DDK)-Mediated Proteolysis of CENP-A Prevents Mislocalization of CENP-A in Saccharomyces cerevisiae

The evolutionarily conserved centromeric histone H3 variant ( in budding yeast, CENP-A in humans) is essential for faithful chromosome segregation. Mislocalization of CENP-A to non-centromeric chromatin contributes to chromosomal instability (CIN) in yeast, fly, and human cells and CENP-A is highly expressed and mislocalized in cancers. Defining mechanisms that prevent mislocalization of CENP-A is an area of active investigation. Ubiquitin-mediated proteolysis of overexpressed (GALCSE4) by E3 ubiquitin ligases such as prevents mislocalization of , and Delta strains display synthetic dosage lethality (SDL) with GALCSE4. We previously performed a genome-wide screen and identified five alleles of and that encode the -dependent kinase (DDK) complex, which regulates DNA replication initiation, among the top twelve hits that displayed SDL with GALCSE4. We determined that -7 strains exhibit defects in ubiquitin-mediated proteolysis of and show mislocalization of . Mutation of (-bob1) bypasses the requirement of for replication initiation and rescues replication defects in a -7 strain. We determined that -bob1 does not rescue the SDL and defects in proteolysis of GALCSE4 in a -7 strain, suggesting a DNA replication-independent role for in proteolysis. The SDL phenotype, defects in ubiquitin-mediated proteolysis, and the mislocalization pattern of in a -7 Delta strain were similar to that of -7 and Delta strains, suggesting that regulates in a pathway that overlaps with . Our results define a DNA replication initiation-independent role of DDK as a regulator of -mediated proteolysis of to prevent mislocalization of .