ELOF1 is a transcription-coupled DNA repair factor that directs RNA polymerase II ubiquitylation

Removal of transcription-blocking DNA lesions requires the binding of transcription-coupled repair (TCR) factors to DNA damage-stalled RNA polymerase II (RNAPII). The full repertoire of factors required for TCR remains to be elucidated. Through genome-wide CRISPR screens and strand-specific ChIP-seq, we identify the RNAPII-associated factor ELOF1 as a new core TCR component. Mechanistically, ELOF1 does not affect the association of TCR components CSB and the CRL4CSA ubiquitin ligase, but instead regulates RNAPII ubiquitylation, and subsequent ubiquitin-dependent recruitment of repair factors. This function requires its constitutive interaction with RNAPII close to the K1268 site, revealing ELOF1 as a specificity factor that positions CRL4CSA for optimal RNAPII ubiquitylation to orchestrate transcription-coupled repair. Finally, ELOF1 operates in a second transcription stress-response pathway, regulated by the deubiquitylating enzyme OTUD5.