Regulation of the Rev1-pol ζ complex during bypass of a DNA interstrand cross-link

DNA interstrand cross-links (ICLs) are repaired in S phase by a complex, multistep mechanism involving translesion DNA polymerases. After replication forks collide with an ICL, the leading strand approaches to within one nucleotide of the ICL ("approach"), a nucleotide is inserted across from the unhooked lesion ("insertion"), and the leading strand is extended beyond the lesion ("extension"). How DNA polymerases bypass the ICL is incompletely understood. Here, we use repair of a site-specific ICL in Xenopus egg extracts to study the mechanism of lesion bypass. Deep sequencing of ICL repair products showed that the approach and extension steps are largely error-free. However, a short mutagenic tract is introduced in the vicinity of the lesion, with a maximum mutation frequency of ~1%. Our data further suggest that approach is performed by a replicative polymerase, while extension involves a complex of Rev1 and DNA polymerase ζ. Rev1-pol ζ recruitment requires the Fanconi anemia core complex but not FancI-FancD2. Our results begin to illuminate how lesion bypass is integrated with chromosomal DNA replication to limit ICL repair-associated mutagenesis. Synopsis Chromosomal DNA replication integrates with translesion DNA synthesis during DNA interstrand cross-link repair to limit mutagenesis. Approach of the leading strand to a DNA interstrand cross-link (ICL) involves a replicative DNA polymerase. A Rev1-pol ζ complex promotes the extension step during ICL repair. Binding of Rev1 to the ICL locus is dependent on the Fanconi anemia core complex. Mutagenesis is limited to a narrow region surrounding the ICL. Chromosomal DNA replication integrates with translesion DNA synthesis during DNA interstrand cross-link repair to limit mutagenesis.