RPA activates the XPF-ERCC1 endonuclease to initiate processing of DNA interstrand crosslinks

Ummi B Abdullah, Joanna F McGouran, Sanja Brolih, Denis Ptchelkine, Afaf H El‐Sagheer, Tom Brown, Peter J McHugh

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During replication-coupled DNA interstrand crosslink (ICL) repair, the XPF-ERCC1 endonuclease is required for the incisions that release, or “unhook”, ICLs, but the mechanism of ICL unhooking remains largely unknown. Incisions are triggered when the nascent leading strand of a replication fork strikes the ICL. Here, we report that while purified XPF-ERCC1 incises simple ICL-containing model replication fork structures, the presence of a nascent leading strand, modelling the effects of replication arrest, inhibits this activity. Strikingly, the addition of the single-stranded DNA (ssDNA)-binding replication protein A (RPA) selectively restores XPF-ERCC1 endonuclease activity on this structure. The 5′–3′ exonuclease SNM1A can load from the XPF-ERCC1-RPA-induced incisions and digest past the crosslink to quantitatively complete the unhooking reaction. We postulate that these collaborative activities of XPF-ERCC1, RPA and SNM1A might explain how ICL unhooking is achieved in vivo.
Original languageEnglish (US)
Pages (from-to)2047-2060
Number of pages14
JournalThe EMBO Journal
Issue number14
StatePublished - Jun 12 2017
Externally publishedYes

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