Mapping of TOP1cc and R-loops im MCF-7 after TOP1 KD and/or RNase H OE [CHiP_DRIP_Seq]

DNA double-stranded breaks (DSBs) pose a significant threat to genomic integrity, and their generation during essential cellular processes like transcription remains poorly understood. In this study, we employed DRIP-seq and ChIP-seq to map the change in TOP1cc and R-loops after the depletion of TOP1 and R-loops, to comprehensively investigate the interplay between transcription, DSBs, Topoisomerase 1 (TOP1), and R-loops. Our findings revealed the presence of DSBs at highly expressed genes enriched with TOP1 and R-loops, indicating their crucial involvement in transcription-associated genomic instability. Depletion of R-loops and TOP1 specifically reduced DSBs at highly expressed genes, uncovering their pivotal roles in transcriptional DSB formation. By elucidating the intricate interplay between TOP1cc trapping, R-loops, and DSBs, our study provides novel insights into the mechanisms underlying transcription-associated genomic instability. Moreover, we establish a link between transcriptional DSBs and early molecular changes driving cancer development. Notably, our study highlights the distinct etiology and molecular characteristics of driver mutations compared to passenger mutations, shedding light on the potential for targeted therapeutic strategies. Overall, these findings deepen our understanding of the regulatory mechanisms governing DSBs in hypertranscribed genes associated with carcinogenesis, opening avenues for future research and therapeutic interventions. Overall design: TOP1cc ChIP-seq and DRIP-seq for MCF-7 cells, for control cells transfected with scramble siRNA and invected with empty vector (EV), cells after TOP1 knockdown (KD), cells after RNase H overexpression (OE), cells after both manipulations (TOP1 KD + RNase H OE).