Figure 3.

Crosstalk between NER and ATR pathways. The NER activity excises a ~30 nucleotide oligomer containing the damage. The resulting excision gap is filled in by DNA polymerases, however, if this process is delayed or defective, the gap can be processed by EXO1 nuclease. Subsequently, a single-strand binding protein RPA covers the extended gap to limit DNA double-strand break. This intermediate structure is favored by the ATR-ATRIP complex and followed by XPA phosphorylation and NER activation, making a positive feedback loop between the two pathways.