biostudies-literatureUnknown222(11)Petsalaki EHellenic Foundation for Research and InnovationFondation SantéIn response to chromatin bridges, the abscission checkpoint delays completion of cytokinesis to prevent chromosome breakage or tetraploidization. Here, we show that spontaneous or replication stress-induced chromatin bridges exhibit "knots" of catenated and overtwisted DNA next to the midbody. Topoisomerase IIα (Top2α) forms abortive Top2-DNA cleavage complexes (Top2ccs) on DNA knots; furthermore, impaired Top2α-DNA cleavage activity correlates with chromatin bridge breakage in cytokinesis. Proteasomal degradation of Top2ccs is required for Rad17 localization to Top2-generated double-strand DNA ends on DNA knots; in turn, Rad17 promotes local recruitment of the MRN complex and downstream ATM-Chk2-INCENP signaling to delay abscission and prevent chromatin breakage. In contrast, dicentric chThe Journal of cell biologye202303123https://www.ebi.ac.uk/biostudies/studies/S-EPMC10461104biostudies-literatureThe abscission checkpoint senses chromatin bridges through Top2α recruitment to DNA knots.PMC10461104Zachos GBalafouti SKyriazi AAPetsalaki EfalseThe abscission checkpoint senses chromatin bridges through Top2α recruitment to DNA knots.In response to chromatin bridges, the abscission checkpoint delays completion of cytokinesis to prevent chromosome breakage or tetraploidization. Here, we show that spontaneous or replication stress-induced chromatin bridges exhibit "knots" of catenated and overtwisted DNA next to the midbody. Topoisomerase IIα (Top2α) forms abortive Top2-DNA cleavage complexes (Top2ccs) on DNA knots; furthermore, impaired Top2α-DNA cleavage activity correlates with chromatin bridge breakage in cytokinesis. Proteasomal degradation of Top2ccs is required for Rad17 localization to Top2-generated double-strand DNA ends on DNA knots; in turn, Rad17 promotes local recruitment of the MRN complex and downstream ATM-Chk2-INCENP signaling to delay abscission and prevent chromatin breakage. In contrast, dicentric ch2023-01-01T00:00:00Z2023 Nov2026-07-14T23:16:19.468Z2025-04-06T12:47:52.536ZS-EPMC104611043763888410.1083/jcb.202303123