Disabling leading and lagging strand histone transmission results in parental histones loss and reduced cell plasticity and viability [ChOR-seq]

In the process of DNA replication, the first steps in restoring the chromatin landscape involve parental histone recycling and new histone deposition. Disrupting histone recycling to either the leading or lagging strand induces asymmetric histone inheritance, impacting epigenome maintenance and cellular identity. However, the order and kinetics of these effects remain elusive. Here, we employ inducible mutants to dissect the early and late consequences of impaired histone recycling. Simultaneous disruption of both leading (POLE4) and lagging strand (MCM2-2A) recycling pathways impairs transmission of parental histones to newly synthesized DNA, with release of some parental histones to the soluble pool. Subsequently, H3K27me3 accumulates aberrantly during chromatin restoration in a manner preceding gene expression changes. Loss of histone inheritance and the ensuing chromatin restoration defects alter gene expression in embryonic stem cells, challenges differentiation programs and cell viability. Our findings demonstrate the importance of efficient transmission of histone-based information during DNA replication for maintaining chromatin landscapes, differentiation potential, and cellular viability. Overall design: ChOR-seq of POLE4-dTAG (1 clone, #555) and POLE4-dTAG/MCM2-2A (2 clones, #557 and #581) mouse embryonic stem cells (DMSO and dTAG treatment). Nascent chromatin samples were collected after 2 hours of DMSO or dTAG treatment.