Trabectedin derails transcription-coupled nucleotide excision repair to induce DNA breaks in highly transcribed genes

ABSTRACT Most genotoxic anticancer agents fail in tumors with intact DNA repair. Therefore, trabectedin, a unique agent more toxic to cells with active DNA repair, specifically transcription-coupled nucleotide excision repair (TC-NER), provides new therapeutic opportunities. To unlock the potential of trabectedin and inform its application in precision oncology, a full mechanistic understanding of the drug’s TC-NER-dependent toxicity is needed. Here, we determined that abortive TC-NER of trabectedin-DNA adducts forms persistent single-strand breaks (SSBs) as the adducts block the second of the two sequential NER incisions. We mapped the 3’-hydroxyl groups of SSBs originating from the first NER incision at trabectedin lesions, recording TC-NER on a genome-wide scale. We showed that trabectedin-induced SSBs primarily occur in transcribed strands of active genes and peak near transcription start sites. Frequent SSBs were also found outside gene bodies, connecting TC-NER to divergent transcription from promoters. This work advances the use trabectedin for precision oncology and for studying TC-NER and transcription.