Quantification of histone H3 and H4 modifications by mass spectrometry in wildtype and MCM2-2A mutants of mice ESCs

During DNA replication modified parental histones H3-H4 are segregated almost symmetrically to the two daughter DNA strands enabling mitotic inheritance of histone PTMs. Whether heritable histone modifications confer epigenetic regulation by maintaining chromatin states and gene expression is unclear. Using MCM2 histone-binding mutant embryonic stem cells (ESCs) and mass spectrometry, we show that asymmetric segregation of parental histones to the leading strand causes imbalanced inheritance of histone H3K27 methylations to daughter cells.