Replication stress alters CENP-A nucleosome stability during S phase

1.The maintenance of centromere identity is essential for the proper segregation of chromosomes during cell division. Centromere identity is epigenetically specified by centromeric histone H3 variant CENP-A, and its retention during DNA replication is facilitated by HJURP chaperone. Replication stress disrupts replication fork progression and can negatively influence the interactions between histone chaperone network necessary for retention and deposition of parental and new histones, respectively. In this study we investigate the role of replication stress response on centromere inheritance. We define changes in centromere-associated proteins that govern stability of centromeric and canonical nucleosomes through proximity labeling coupled with affinity purification mass spectrometry. We identified that under replication stress, CENP-A-containing chromatin strongly enriches for SWI/SNF chromatin remodeling proteins ATRX. We show that depletion of ATRX and its associated histone H3.3 chaperone DAXX results in the loss CENP-A retention in S-phase and loss persists into the subsequent cell cycle. Altogether our findings provide insight into how replication stress negatively influences centromeric chromatin instability and delineates a function of DAXX-ATRX complex in maintaining centromere inheritance during DNA replication.