Repair of a DNA-Protein Crosslink by Replication-Coupled Proteolysis

• Cell-free repair of a DNA-protein crosslink (DPC)
• DPC repair is coupled to DNA replication
• Replication triggers DPC proteolysis, yielding a DNA-peptide adduct
• Bypass of the peptide adduct requires DNA pol ζ

SummaryDNA-protein crosslinks (DPCs) are caused by environmental, endogenous, and chemotherapeutic agents and pose a severe threat to genome stability. We use Xenopus egg extracts to recapitulate DPC repair in vitro and show that this process is coupled to DNA replication. A DPC on the leading strand template arrests the replisome by stalling the CMG helicase. The DPC is then degraded on DNA, yielding a peptide-DNA adduct that is bypassed by CMG. The leading strand subsequently resumes synthesis, stalls again at the adduct, and then progresses past the adduct using DNA polymerase ζ. A DPC on the lagging strand template only transiently stalls the replisome, but it too is degraded, allowing Okazaki fragment bypass. Our experiments describe a versatile, proteolysis-based mechanism of S phase DPC repair that avoids replication fork collapse.

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