STK19 accelerates the clearance of lesion-stalled RNAPII to facilitate transcription-coupled DNA repair

Transcription-coupled DNA repair (TCR) removes bulky DNA lesions impeding RNA polymerase II (RNAPII) transcription. Recent studies have outlined the stepwise assembly of TCR factors CSB, CSA, UVSSA, and TFIIH around lesion-stalled RNAPII. However, the mechanism and factors required for the transition to downstream repair steps, including RNAPII removal to provide repair proteins access to the DNA lesion, remain unclear. Here, we identify STK19 as a new TCR factor facilitating this transition. Loss of STK19 does not impact initial TCR complex assembly or RNAPII ubiquitylation but delays lesion-stalled RNAPII clearance, thereby interfering with the downstream repair reaction. Cryo-EM and mutational analysis reveal that STK19 associates with the TCR complex, positioning itself between RNAPII, UVSSA, and CSA. The structural insights and molecular modelling suggest that STK19 positions the ATPase subunits of TFIIH onto DNA in front of RNAPII. Together, these findings provide new insights into the factors and mechanisms required for TCR. HEK293 FlpIn TRex cells wild type, STK19 KO or CSB KO were used in order to assess transcription recovery after UVC irradiation. Cells were either left untreated or treated with 15J/m2 UVC and left to grow for the speficied time (2h, 5h, 12h, 24h or 36h). Cells were then harvested and submited to the TTchem-seq (Gregersen et al., 2020) to look at the effects in nascent transcription of STK19 knock out in HEK293 FlpIn TREx cells with CSB KO as control cell line .