Accurate recycling of parental histones reproduces the histone modification landscape during DNA replication

Chromatin organisation is disrupted genome wide during DNA replication. On newly synthesized DNA, nucleosomes are assembled from new naïve histones and old modified histones. It remains unknown whether the landscape of histone post-translational modifications (PTMs) is copied during DNA replication or the epigenomeis perturbed. Here we develop Chromatin Occupancy after Replication, ChOR-seq, a technology that combines chromatin immunopreciptation of histone marks and purification of newly replicated DNA by streptavidin pull-down followed by next generation sequencing. We use this technology to address propagation of epigenetic states across cell division and reveal that accurate recycling of modified parental histones ensures that positional information of histone marks is faithfully reproduced on daughter strands and inherited to daughter cells. Analysis of H3K27me3 and total H3 distribution and abundance after replication and across the cell cycle by ChOR-seq in HeLa S3 cells. All experiments were done in duplicates. Replicated chromatin was labelled in mid S. Chromatin of Drosophila melanogater S2 cells were used as spike-in for normalization purpose.