The centromeric histone H3 variant CENP-A is overexpressed in many cancers. The mislocalization of CENP-A to noncentromeric regions contributes to chromosomal instability (CIN), a hallmark of cancer. However, pathways that promote or prevent CENP-A mislocalization remain poorly defined. Here, we performed a genome-wide RNAi screen for regulators of CENP-A localization which identified DNAJC9, a J-domain protein implicated in histone H3–H4 protein folding, as a factor restricting CENP-A mislocalization. Cells lacking DNAJC9 exhibit mislocalization of CENP-A throughout the genome, and CIN phenotypes. Global interactome analysis showed that DNAJC9 depletion promotes the interaction of CENP-A with the DNA-replication-associated histone chaperone MCM2. CENP-A mislocalization upon DNAJC9 depletion was dependent on MCM2, defining MCM2 as a driver of CENP-A deposition at ectopic sites when H3–H4 supply chains are disrupted. Cells depleted for histone H3.3, also exhibit CENP-A mislocalization. In summary, we have defined novel factors that prevent mislocalization of CENP-A, and demonstrated that the integrity of H3–H4 supply chains regulated by histone chaperones such as DNAJC9 restrict CENP-A mislocalization and CIN.
Synopsis: Centromeric localization of the histone H3 variant CENP-A is critical for faithful chromosome segregation. This study reveals that the histone H3 chaperone DNAJC9 restricts mislocalization of CENP-A to non-centromeric regions, and thereby prevents chromosome instability (CIN).Loss of DNAJC9 leads to enrichment of CENP-A at the non-centromeric regions genome-wide.Mislocalization of CENP-A enhances the CIN phenotypes of DNAJC9-depleted cells.DNA replication-associated H3 chaperone MCM2 contributes to CENP-A mislocalization upon DNAJC9 depletion.
Genome-wide RNAi screens reveal the importance of proper histone H3-H4 folding/supply for restricting CENP-A localization to centromeres.