Elongation factor ELOF1 drives transcription-coupled repairand prevents genome instability [DRB-TTchem-seq]

Correct transcription is crucial for life. However, DNA damage severely impedes elongating RNA Polymerase II (Pol II), causing transcription inhibition and transcription-replication conflicts. Cells have evolved intricate mechanisms to counteract the severe consequence of these transcription-blocking lesions, however the exact mechanism and factors involved remain largely unknown. Here, using a genome-wide CRISPR/cas9 screen, we identified elongation factor ELOF1 as an important new factor in the damage-induced transcription stress response. ELOF1 has an evolutionary-conserved role in TC-NER where it promotes the recruitment of the TC-NER factors UVSSA and TFIIH and facilitates Pol II ubiquitylation to efficiently repair TBLs. Importantly, ELOF1 has an additional role in protecting cells from transcription-mediated replication hindrance, thereby preserving genome stability. Thus, ELOF1 protects the transcription machinery from DNA damage by two distinct mechanisms. Determining the elongation rates in HCT116 wt, ELOF1 KO, CSB KO or ELOF1 KO+ ELOF1-GFP cells using DRB-TTchem-seq. transient transcriptome sequencing (TT-seq); 3.5 hrs pre-treatment with 100uM DRB (5,6-dichloro-1-β-D-ribofuranosylbenzimidazole), followed by release from DRB inhibition for 10, 20, 30 or 40 min (including 10 min 1mM 4-thiouridine pulse)