ELOF1 (elongation factor 1) is a critical component of transcription-coupled nucleotide excision repair (TC-NER) that serves as a key adapter protein anchoring repair factors to RNA polymerase II (RNAPII) 123. The protein facilitates the recruitment of TC-NER factors UVSSA and the CRL4CSA ubiquitin ligase complex to lesion-stalled RNAPII, leading to site-specific ubiquitylation of RNAPII at lysine K1268 23. This ubiquitylation event is essential for RNAPII inactivation and the assembly of downstream repair factors required to remove transcription-blocking DNA lesions 3. ELOF1 constitutively interacts with RNAPII and positions CRL4CSA for optimal ubiquitylation specificity 2. Beyond DNA repair, ELOF1 stabilizes paused RNAPII at transcription barriers and prevents transcription-mediated replication stress, thereby maintaining genome stability 14. The protein is also required for activation-induced cytidine deaminase (AID) targeting during antibody diversification, facilitating somatic hypermutation and class switch recombination in B cells 45. ELOF1 deficiency results in increased sensitivity to DNA-damaging agents and compromised immune responses 65.