Double incision at the damaged DNA strand excises the oligonucleotide that contains the lesion from the open bubble. The excised oligonucleotide is ~27-30 bases long. Incision 5' to the damage site, by ERCC1:ERCC4 endonuclease, precedes the incision 3' to the damage site by ERCC5 endonuclease (Staresincic et al. 2009).
