Ayra-Plasencia, JesselJorge, InmaculadaVázquez, JesúsFreire, RaimundoSmits, Veronique A J2026-07-162026-07-162026-04-16Cell Rep. 2026 Apr 16;45(4):117279.https://hdl.handle.net/20.500.12105/27595DNA double-strand breaks generated during mitosis are thought to be inefficiently repaired, yet cellular responses to damage incurred specifically in late mitosis remain poorly understood. Here, we report that irradiation of cells synchronized in anaphase/telophase triggers partial DNA damage signaling, marked by H2AX phosphorylation and MDC1 accumulation. Consequently, cells enter G1 and S phases with unrepaired lesions. Proteomic analysis identified the E3 ubiquitin ligases RNF126 and BRAP as key regulators of this response, based on their selective ATM-dependent accumulation in irradiated late mitotic cells. Functional assays reveal that both proteins are required for damage-induced 53BP1 and RPA2 focus formation, resolution of DNA lesions, and survival after damage in late mitosis. Supporting their clinical relevance, both E3 ligases are overexpressed in selected tumors and associated with chromosomal instability. These findings suggest that RNF126 and BRAP help cells tolerate late mitotic damage and may represent potential vulnerabilities for improving genotoxic therapies in cancer.We thank all members of V.A.J.S.’s and R.F.’s laboratories for helpful discussions throughout this study. We are especially grateful to Irene Izquierdo La Serna for her assistance in obtaining raw data for CIN70 score analysis. This work was supported by grants PID2022-139691OB-I00 to V.A.J.S. and R.F., and PID2021-122348NB-I00 to J.V., funded by MICIU/AEI/10.13039/501100011033 and ERDF/EU; grant PIFIISC23/26, funded by Fundación Canaria Instituto de Investigación Sanitaria de Canarias, to V.A.J.S.; grants PLEC2022-009298, PLEC2022-009235, and EQC2021-007053-P, funded by MICIU/AEI/10.13039/501100011033 and European Union NextGenerationEU/PRTR, and S2022/BMD-7333-CM, funded by Comunidad de Madrid, to J.V. The project leading to these results has received funding from the "La Caixa" Foundation under the project code LCF/PR/HR22/52420019 to J.V. J.A.-P. was supported by Juan de la Cierva Formación fellowship FJC2021-046566-I, funded by MICIU/AEI/10.13039/501100011033 and European Union NextGenerationEU/PRTR. The CNIC is supported by the Instituto de Salud Carlos III, the Ministerio de Ciencia, Innovación y Universidades, and the Pro CNIC Foundation and is a Severo Ochoa Center of Excellence (grant CEX2020-001041-S, funded by MICIU/AEI/10.13039/501100011033).engVoRhttp://creativecommons.org/licenses/by-nc-nd/4.0/BRAPCP: genomicsDNA damage responseRNF126cell cycle checkpointchromosomal instabilitydouble-strand breakionizing radiationlate mitosisreplication stressubiquitin ligaseAttribution-NonCommercial-NoDerivatives 4.0 International41996237CELL REPORTSopen access