The histone chaperone FACT coordinates H2A.X-dependent signaling and repair of DNA damage

SUMMARY Safeguarding cell function and identity following a genotoxic stress challenge entails a tight coordination of DNA damage signaling and repair with chromatin maintenance. How this coordination is achieved and with what impact on chromatin integrity remains elusive. Here, by investigating the mechanisms governing the distribution of H2A.X in mammalian chromatin, we demonstrate that this histone variant is deposited de novo at sites of DNA damage in a repair synthesis-coupled manner. Our mechanistic studies further identify the histone chaperone FACT (Facilitates Chromatin Transcription) as responsible for the deposition of newly synthesized H2A.X. Functionally, FACT potentiates H2A.X-dependent signaling of DNA damage and, together with ANP32E (Acidic Nuclear Phosphoprotein 32 Family Member E), orchestrates a H2A.Z/H2A.X exchange reaction that reshapes the chromatin landscape at repair sites. We propose that this mechanism promotes chromatin accessibility and helps tailoring DNA damage signaling to repair progression. HIGHLIGHTS H2A.X, but not H2A.Z, is deposited de novo at sites of DNA damage repair FACT promotes new H2A.X deposition coupled to repair synthesis FACT and ANP32E chaperones orchestrate H2A.Z/H2A.X exchange in damaged chromatin FACT stimulates H2A.X-dependent signaling of DNA damage