The proteomic landscape of genotoxic stress-induced micronuclei

SUMMARY Micronuclei (MN) are induced by various genotoxic stressors and amass nuclear- and cytoplasmic-resident proteins, priming the cell for MN-driven signalling cascades. Here, we measure the proteome of micronuclear, cytoplasmic, and nuclear fractions from human cells exposed to a panel of six genotoxins, comprehensively profiling their MN protein landscape. We find that MN assemble a proteome distinct from both surrounding cytoplasm and parental nuclei, with a core composition that is independent of the specific inciting stressor. Across stress conditions, MN are significantly depleted for spliceosome machinery and replication stress response proteins, but are enriched for a subset of the replisome. We find that the loss of splicing machinery within transcriptionally active MN contributes to intra-MN DNA damage, a known precursor to chromothripsis. This dataset represents a unique resource detailing the proteomic landscape of MN, guiding mechanistic studies of MN generation and MN-associated outcomes of genotoxic stress.