STK19 is a transcription-coupled repair factor that participates in UVSSA ubiquitination and TFIIH loading.

Transcription-coupled repair (TCR) is the major pathway to remove transcription-blocking lesions. Although discovered for nearly 40 years, the mechanism and critical players of mammalian TCR remain unclear. STK19 is a factor affecting cell survival and recovery of RNA synthesis in response to DNA damage, however, whether it is a necessary component for TCR is unknown. Here, we demonstrated that STK19 is essential for human TCR. Mechanistically, STK19 is recruited to damage sites through direct interaction with CSA. It can also interact with RNA polymerase II in vitro. Once recruited, STK19 plays an important role in UVSSA ubiquitination which is needed for TCR. STK19 also promotes TCR independent of UVSSA ubiquitination by stimulating TFIIH recruitment through its direct interaction with TFIIH. In summary, our results suggest that STK19 is a key factor of human TCR that links CSA, UVSSA ubiquitination and TFIIH loading, shedding light on the molecular mechanisms of TCR.