A short G1 phase imposes constitutive replication stress and fork remodelling in mouse embryonic stem cells.

摘要: Embryonic stem cells (ESCs) represent a transient biological state, where pluripotency is coupled with fast proliferation. ESCs display constitutively active DNA damage response (DDR), but its molecular determinants have remained elusive. Here we show in cultured and mouse embryos that H2AX phosphorylation dependent on Ataxia telangiectasia Rad3 related (ATR) associated chromatin loading of the ssDNA-binding proteins RPA RAD51. Single-molecule analysis replication intermediates reveals massive ssDNA gap accumulation, reduced fork speed frequent reversal. All these marks stress do not impair mitotic process are rapidly lost at differentiation onset. Delaying G1/S transition allows formation 53BP1 nuclear bodies suppresses slowing reversal following S-phase. Genetic inactivation leads to chromosomal breakage unperturbed ESCs. We propose rapid cell cycle progression makes effective replication-coupled mechanisms protect genome integrity.