DNAJC9 prevents CENP-A mislocalization and chromosomal instability by maintaining the fidelity of H3-H4 supply chains

The centromeric histone H3 variant CENP-A is overexpressed in many cancers. Mislocalization of CENP-A to non-centromeric regions contributes to chromosomal instability (CIN), a hallmark of cancer. Despite these observations, pathways that promote and prevent CENP-A mislocalization remain poorly defined. Here, we performed a genome-wide RNAi screen to identify regulators of CENP-A localization. We identified DNAJC9, a J-domain protein as a lead candidate from the screen and showed that cells depleted for DNAJC9 exhibit mislocalization of CENP-A, enrichment of CENP-A in chromatin, and CIN phenotypes. Global interactome analysis showed an enhanced interaction of CENP-A with the replication-associated H3-H4 chaperone MCM2 in DNAJC9-depleted cells and co-depletion of MCM2 and DNAJC9 suppressed CENP-A mislocalization. Furthermore, we showed that cells ablated for the ability of DNAJC9 to promote the proper folding of H3–H4, exhibit CENP-A mislocalization. CUT&RUN Sequencing analysis of genome-wide CENP-A occupancy in DNAJC9-depleted cells identified 16,603 sites of non-centromeric localization, that broadly overlapped with open chromatin regions. Our comprehensive analysis has identified factors that prevent mislocalization of CENP-A and has defined DNAJC9 as an important safeguard that prevents CENP-A mislocalization and CIN.