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, which plays a central role in damage signaling, is deposited de novo at damage sites 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 and orchestrating, together with ANP32E (Acidic Nuclear Phosphoprotein 32 Family Member E), a H2A.Z/H2A.X exchange reaction, which reshapes the chromatin landscape at repair sites. We propose that this mechanism promotes chromatin accessibility to repair machineries and helps tailoring damage signaling to repair progression.
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-mediated H2A.X deposition is dispensable for DNA damage repair
FACT and ANP32E chaperones orchestrate H2A.Z/H2A.X exchange in UV-damaged chromatin