ERCC8 encodes the CSA protein, which functions as a substrate-recognition component of the CSA complex, a DCX E3 ubiquitin ligase involved in transcription-coupled nucleotide excision repair (TC-NER) 1. The primary function involves recruiting to lesion-stalled RNA polymerase II and mediating ubiquitination of the POLR2A subunit at lysine 1268, a critical checkpoint that governs RNA polymerase II stability and initiates DNA damage excision 1. ERCC8 also promotes ubiquitination and proteasomal degradation of ERCC6/CSB in a UV-dependent manner, essential for recovery of RNA synthesis after transcription-coupled repair 1. Recent findings demonstrate ERCC8's role in transcription-coupled DNA-protein crosslink repair, functioning independently of SPRTN but requiring the CRL4CSA ubiquitin ligase and proteasome 1. Disease relevance includes Cockayne syndrome A, caused by ERCC8 mutations leading to neurological impairment, dwarfism, and photosensitivity 2. Clinical significance extends beyond rare diseases, with genetic variants associated with increased breast cancer susceptibility, particularly through interactions with ERCC6 3, and potential roles in gastric cancer risk when combined with H. pylori infection 4. ERCC8 represents a master regulator coordinating DNA repair with transcription and cell division through ubiquitination mechanisms 5.