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  • Mitotic tethering enables inheritance of shattered micronuclear chromosomes.

Mitotic tethering enables inheritance of shattered micronuclear chromosomes.

Nature (2023-06-15)
Prasad Trivedi, Christopher D Steele, Franco K C Au, Ludmil B Alexandrov, Don W Cleveland
ABSTRACT

Chromothripsis, the shattering and imperfect reassembly of one (or a few) chromosome(s)1, is an ubiquitous2 mutational process generating localized and complex chromosomal rearrangements that drive genome evolution in cancer. Chromothripsis can be initiated by mis-segregation errors in mitosis3,4 or DNA metabolism5-7 that lead to entrapment of chromosomes within micronuclei and their subsequent fragmentation in the next interphase or following mitotic entry6,8-10. Here we use inducible degrons to demonstrate that chromothriptically produced pieces of a micronucleated chromosome are tethered together in mitosis by a protein complex consisting of mediator of DNA damage checkpoint 1 (MDC1), DNA topoisomerase II-binding protein 1 (TOPBP1) and cellular inhibitor of PP2A (CIP2A), thereby enabling en masse segregation to the same daughter cell. Such tethering is shown to be crucial for the viability of cells undergoing chromosome mis-segregation and shattering after transient inactivation of the spindle assembly checkpoint. Transient, degron-induced reduction in CIP2A following chromosome micronucleation-dependent chromosome shattering is shown to drive acquisition of segmental deletions and inversions. Analyses of pancancer tumour genomes showed that expression of CIP2A and TOPBP1 was increased overall in cancers with genomic rearrangements, including copy number-neutral chromothripsis with minimal deletions, but comparatively reduced in cancers with canonical chromothripsis in which deletions were frequent. Thus, chromatin-bound tethers maintain the proximity of fragments of a shattered chromosome enabling their re-encapsulation into, and religation within, a daughter cell nucleus to form heritable, chromothriptically rearranged chromosomes found in the majority of human cancers.

MATERIALS
Product Number
Brand
Product Description

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Anti-phospho-Histone H2A.X (Ser139) Antibody, clone JBW301, clone JBW301, Upstate®, from mouse
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dTAG-13, ≥98% (HPLC)
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MPS1 Inhibitor, NMS-P715, The MPS1 Inhibitor, NMS-P715 controls the biological activity of MPS1. This small molecule/inhibitor is primarily used for Phosphorylation & Dephosphorylation applications.
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RO-3306, ≥98% (HPLC)