Single-stranded structure-specific DNA endonuclease involved in DNA excision repair (PubMed:8206890, PubMed:8090225, PubMed:8078765, PubMed:7651464, PubMed:32821917, PubMed:32522879). Makes the 3'incision in DNA nucleotide excision repair (NER) (PubMed:8090225, PubMed:8078765, PubMed:32821917, PubMed:32522879). Binds and bends DNA repair bubble substrate and breaks base stacking at the single-strand/double-strand DNA junction of the DNA bubble (PubMed:32522879). Plays a role in base excision repair (BER) by promoting the binding of DNA glycosylase NTHL1 to its substrate and increasing NTHL1 catalytic activity that removes oxidized pyrimidines from DNA (PubMed:9927729). Involved in transcription-coupled nucleotide excision repair (TCR) which allows RNA polymerase II-blocking lesions to be rapidly removed from the transcribed strand of active genes (PubMed:16246722). Functions during the initial step of TCR in cooperation with ERCC6/CSB to recognized stalled RNA polymerase II (PubMed:16246722). Also, stimulates ERCC6/CSB binding to the DNA repair bubble and ERCC6/CSB ATPase activity (PubMed:16246722). Required for DNA replication fork maintenance and preservation of genomic stability (PubMed:26833090, PubMed:32522879). Involved in homologous recombination repair (HRR) induced by DNA replication stress by recruiting RAD51, BRCA2, and PALB2 to the damaged DNA site (PubMed:26833090). During HRR, binds to the replication fork with high specificity and stabilizes it (PubMed:32522879). Also, acts upstream of HRR, to promote the release of BRCA1 from DNA (PubMed:26833090). Binds 2 magnesium ions per subunit. They probably participate in the reaction catalyzed by the enzyme. May bind an additional third magnesium ion after substrate binding. Optimum pH is 6.5-7. Monomer (PubMed:32522879). Homodimer (PubMed:32522879). Component of the homologous recombination repair (HR) complex composed of ERCC5/XPG, BRCA2, PALB2, DSS1 and RAD51 (PubMed:26833090). Within the complex, interacts with BRCA2 and PALB2 (PubMed:26833090). Interacts with RNA polymerase II (PubMed:16246722). Interacts (via C-terminus) with ERCC6/CSB; the interaction stimulates ERCC6/CSB binding to the DNA repair bubble and ERCC6/CSB ATPase activity (PubMed:16246722). May form a complex composed of RNA polymerase II, ERCC6/CSB and ERCC5/XPG which associates with the DNA repair bubble during transcription-coupled nucleotide excision repair (PubMed:16246722). Interacts with BRCA1; the interaction promotes the release of BRCA1 from DNA (PubMed:26833090). Interacts with PCNA (PubMed:9305916). Interacts with NTHL1; the interaction stimulates NTHL1 activity and NTHL1 binding to its DNA substrate (PubMed:9927729). Colocalizes with RAD51 to nuclear foci in S phase (PubMed:26833090). Localizes to DNA double-strand breaks (DBS) during replication stress (PubMed:26833090). Colocalizes with BRCA2 to nuclear foci following DNA replication stress (PubMed:26833090). Induced by replication stress caused by DNA double-strand breaks (DBS). Both nuclear localization signals 1 and 2 act as a monopartite signal which binds to the high affinity site on KPNA2/importin-alpha. Both the spacer region (also known as the recognition (R) domain) and C-terminal domain are required for stable binding to the DNA repair bubble (PubMed:16246722). However, both domains are dispensable for incision of DNA bubble structures (PubMed:16246722, PubMed:32821917, PubMed:32522879). The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Includes a cryptic exon found in intron 6. Belongs to the XPG/RAD2 endonuclease family. XPG subfamily. A paper describing an additional role for this protein in a base excision repair pathway that is not coupled to transcription has been retracted, because some of the experimental data were incorrect.