R-loop disruption triggers irreversible topoisomerase 1–DNA cleavage complex formation during AID-dependent IgH gene diversification

Proceedings of the National Academy of Sciences, Volume 123, Issue 14, April 2026. <br/>SignificanceClass switch recombination (CSR) and somatic hypermutation are essential for antibody diversity, dependent on activation-induced cytidine deaminase (AID). Cytidine-to-uridine (C-to-U) editing by AID creates an irreversible topoisomerase 1 (…