Fig. 3: Recruitment of CIP2A–TOPBP1 to ruptured micronuclei poises acentric fragments for clustering upon mitotic entry.
From: Mitotic clustering of pulverized chromosomes from micronuclei
a, Intensity measurements of distinct CIP2A localization patterns in micronuclei compared with to the cytoplasmic pool. The box plots show the median (centre line) and the interquartile range (box limits) with the minimum–maximum values (whiskers). n = 392 (none), n = 99 (diffuse), n = 23 (puncta) micronuclei from 3 independent experiments. Example images are provided in Extended Data Fig. 6. b, The frequency of TOPBP1-positive micronuclei with the indicated patterns of CIP2A across a panel of human cell lines containing micronuclei induced by various methods. Data are mean. From left to right, n = 165, 33, 182, 27, 290, 85, 208, 40, 247 and 25 micronuclei pooled from 2 (DLD-1 and HeLa) or 3 (RPTEC and RPE-1) independent experiments. c, Co-localization of CIP2A and TOPBP1 puncta in micronuclei of DLD-1 cells with Y-chromosome micronuclei (top) and HeLa cells with micronuclei containing random chromosomes (bottom). Scale bar, 10 μm. d, Time-lapse example of interphase CIP2A–HaloTag signal in a ruptured micronucleus (lacking sfGFP–NLS) through mitotic entry and the completion of mitosis. The yellow asterisks denote the two newly formed daughter cells. NEBD, nuclear envelope breakdown. Scale bar, 5 μm. e, Examples of mitotic chromosomes showing a highly specific association between CIP2A and clusters of γH2AX-positive Y-chromosome fragments (+DOX/IAA) but not γH2AX-negative Y chromosomes (−DOX/IAA). Scale bar, 10 μm. f, Quantification of CIP2A localization on Y chromosomes with and without γH2AX from e. Data are mean ± s.e.m. n = 3 independent experiments; 611 (γH2AX−) and 200 (γH2AX+) mitotic cells. g, Schematic of the stepwise series of events resulting in the premature engagement of CIP2A–TOPBP1 with DNA lesions following micronuclear envelope rupture during interphase.
