Substrate-recognition component of the CSA complex, a DCX (DDB1-CUL4-X-box) E3 ubiquitin-protein ligase complex, involved in transcription-coupled nucleotide excision repair (TC-NER), a process during which RNA polymerase II-blocking lesions are rapidly removed from the transcribed strand of active genes (PubMed:12732143, PubMed:16751180, PubMed:16964240, PubMed:32142649, PubMed:34526721, PubMed:38316879, PubMed:38600235, PubMed:38600236). Following recruitment to lesion-stalled RNA polymerase II (Pol II), the CSA complex mediates ubiquitination of Pol II subunit POLR2A/RPB1 at 'Lys- 1268', a critical TC-NER checkpoint, governing RNA Pol II stability and initiating DNA damage excision by TFIIH recruitment (PubMed:12732143, PubMed:16751180, PubMed:16964240, PubMed:32142649, PubMed:32355176, PubMed:34526721, PubMed:38316879, PubMed:38600235, PubMed:38600236). The CSA complex also promotes the ubiquitination and subsequent proteasomal degradation of ERCC6/CSB in a UV-dependent manner; ERCC6 degradation is essential for the recovery of RNA synthesis after transcription-coupled repair (PubMed:16751180). Also plays a role in DNA double-strand breaks (DSSBs) repair by non-homologous end joining (NHEJ) (PubMed:29545921). {ECO:0000269|PubMed:12732143, ECO:0000269|PubMed:16751180, ECO:0000269|PubMed:16964240, ECO:0000269|PubMed:29545921, ECO:0000269|PubMed:32142649, ECO:0000269|PubMed:32355176, ECO:0000269|PubMed:34526721, ECO:0000269|PubMed:38316879, ECO:0000269|PubMed:38600235, ECO:0000269|PubMed:38600236}. This is the function of ERCC8 (ERCC excision repair 8, CSA ubiquitin ligase complex subunit, Ensembl gene identifier ENSG00000049167).