Figure 4.

Late NER stages: dual incision, resynthesis, and ligation. The first incision is carried out by XPF–ERCC1 from the 5′ side to the lesion site. Then, replication machinery is loaded, and repair synthesis can be initiated. Possible sets of replication machines: DNA polymerase δ, PCNA, and RFC; DNA polymerase ε, PCNA, and a modified form of RFC; or DNA polymerase κ, ubiquitinated PCNA, and XRCC1. Halfway gap resynthesis is followed by a second incision by XPG. After repair synthesis is completed, nick sealing is performed by DNA ligase I or by the DNA ligase IIIα–XRCC1 complex.