DNA polymerase ε harmonizes topological states and R-loops formation to maintain genome integrity in Arabidopsis

Genome topology is tied to R-loop formation and genome stability. However, the regulatory mechanism remains to be elucidated. By establishing a system to sense the connections between R-loops and genome topology states, we show that inhibiting DNA topoisomerase 1 (TOP1i) triggers the global increase of R-loops (called topoR-loops) and DNA damages, which are exacerbated in the DNA damage repair-compromised mutant atm. Further suppressor screen identifies a mutation in POL2A, the catalytic subunit of DNA polymerase ?, liberating the TOP1i-induced topoR-loop accumulation and genome instability in atm. Additionally, we find a highly conserved junction domain between the exonuclease and polymerase domains in POL2A that is required for modulating topoR-loops near DNA replication origins and facilitating faithful DNA replication. Our results suggest that DNA replication is in concert with genome topological states to fine-tune R-loops and thereby maintain genome integrity, revealing a presumably conserved regulatory mechanism of TOP1i resistance in chemotherapy for ATM-deficient cancers. ssDRIP performed using S9.6 antibody of root with TOP1i or DMSO (control) treatment in Col-0 (WT), atm, asr20 and pol2a mutants