KAT6 and KAT7 actively maintain mitotic chromatin composition and acetylation to preserve developmental competence

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Abstract
Mitotic bookmarking enables transmission of regulatory information across cell division, yet how active chromatin states are molecularly preserved during mitosis and how they contribute to postmitotic cell fate decisions remain unresolved. Here, we demonstrate that the acetyltransferases KAT6 and KAT7 remain chromatin-bound and catalytically active throughout mitosis in mouse and human pluripotent stem cells. Acute KAT6/7 depletion disrupts mitotic histone acetylation and the retention of multiple chromatin regulators with minimal effects on chromatin accessibility. Mechanistically, KAT6/7 bookmark both self renewal and developmental gene loci, where they are required for post-mitotic transcriptional reactivation and priming of lineage-specific programs. Consistently, genes impaired during postmitotic reactivation also fail to activate during neuronal differentiation upon continuous KAT6/7 perturbation, compromising the establishment of the neuronal program and identity. Altogether, our findings identify KAT6 and KAT7 as a cooperative mitotic chromatin maintenance system that couples active histone acetylation to preservation of chromatin composition, transcriptional memory, and developmental competence across cell division, extending the bookmarking function beyond transcriptional memory. These findings also provide a new framework for understanding KAT6/7 function in neurodevelopmental disorders and cancer.