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Published on: August 2, 2024
The proteomic landscape of genotoxic stress-induced micronuclei
Kate M MacDonald1, Shahbaz Khan2, Brian Lin1
1Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1L7, Canada.
Abstract:
Micronuclei (MN) are induced by various genotoxic stressors and amass nuclear- and cytoplasmic-resident proteins, priming the cell for MN-driven signaling cascades. Here, we measured 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, depleted of spliceosome and DNA damage repair components while enriched for a subset of the replisome. We show that the depletion of splicing machinery within transcriptionally active MN contributes to intra-MN DNA damage, a known precursor to chromothripsis. The presence of transcription machinery in MN is stress-dependent, causing a contextual induction of MN DNA damage through spliceosome deficiency. This dataset represents a unique resource detailing the global proteome of MN, guiding mechanistic studies of MN generation and MN-associated outcomes of genotoxic stress.
Insights
Micronuclei (MN) gather distinct proteins, differing from nuclear and cytoplasmic fractions. This protein assembly within MN can lead to DNA damage and chromothripsis under genotoxic stress.
Area of Science:
- Cell Biology
- Genomics
- Proteomics
Background:
- Micronuclei (MN) are cellular structures formed by genotoxic events.
- These structures accumulate proteins, influencing cellular signaling pathways.
- Understanding the protein composition of MN is crucial for deciphering their role in disease.
Purpose of the Study:
- To comprehensively profile the proteome of micronuclear fractions.
- To compare the MN proteome with nuclear and cytoplasmic fractions.
- To investigate the functional consequences of MN protein composition on DNA damage.
Main Methods:
- Human cells were exposed to six different genotoxins.
- Proteomic analysis was performed on isolated micronuclear, cytoplasmic, and nuclear fractions.
- Bioinformatic analysis was used to identify protein enrichment and depletion patterns.
Main Results:
- Micronuclei (MN) assemble a unique proteome distinct from nuclear and cytoplasmic fractions.
- MN proteomes are depleted of spliceosome and DNA damage repair proteins.
- MN are enriched for a subset of the replisome, and transcription machinery presence is stress-dependent.
Conclusions:
- The distinct proteome of MN, particularly the depletion of splicing machinery, contributes to intra-MN DNA damage.
- This intra-MN DNA damage is a precursor to chromothripsis.
- The findings provide a resource for understanding MN formation and genotoxic stress outcomes.
