Evidence of centromeric histone 3 chaperone involved in DNA damage repair pathway in budding yeast.

The centromeric protein-A (CENP-A) is an evolutionarily conserved histone H3 variant that marks the identity of the centromeres. Several mechanisms regulate the centromeric deposition of CENP-A as its mislocalization causes erroneous chromosome segregation, leading to aneuploidy-based diseases, including cancers. The most crucial deposition factor is a CENP-A specific chaperone, HJURP (Scm3 in budding yeast), which specifically binds to CENP-A. However, the discovery of HJURP as a DDR (DNA damage repair) protein and evidence of its binding to Holliday junctions in vitro indicate a CENP-A-deposition-independent role of these chaperones. In this study, using budding yeast, we demonstrate that Scm3 is crucial for the DDR pathway as Scm3-depleted cells are sensitive to DNA damage. We further observe that Scm3 depletion genetically interacts with the rad52 DDR mutant and is compromised in activating DDR-mediated arrest. We demonstrate that Scm3 associates with DNA damage sites and undergoes posttranslational modifications upon DNA damage. Overall, from this report and earlier studies on HJURP, we conclude that DDR functions of CENP-A chaperones are conserved across eukaryotes. The revelation that these chaperones promote genome stability in more than one pathway has clinical significance.