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bioRxiv
BIORXIV
bioRxiv
2692-8205
Cold Spring Harbor Laboratory

10.1101/2024.09.02.610809
preprint
1
Article
Aneuploidy of Specific Chromosomes is Beneficial to Cells Lacking Spindle Checkpoint Protein Bub3
Gadgil Pallavi
Ballew Olivia
Sullivan Timothy J.
Lacefield Soni http://orcid.org/0000-0002-2862-5067

03 9 2024
2024.09.02.610809https://creativecommons.org/licenses/by-nc-nd/4.0/ This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which allows reusers to copy and distribute the material in any medium or format in unadapted form only, for noncommercial purposes only, and only so long as attribution is given to the creator.
http://biorxiv.org/lookup/doi/10.1101/2024.09.02.610809
nihpp-2024.09.02.610809.pdf
ABSTRACT

Aneuploidy typically poses challenges for cell survival and growth. However, recent studies have identified exceptions where aneuploidy is beneficial for cells with mutations in certain regulatory genes. Our research reveals that cells lacking the spindle checkpoint gene BUB3 exhibit aneuploidy of select chromosomes. While the spindle checkpoint is not essential in budding yeast, the loss of BUB3 and BUB1 increases the probability of chromosome missegregation compared to wildtype cells. Contrary to the prevailing assumption that the aneuploid cells would be outcompeted due to growth defects, our findings demonstrate that bub3 Δ cells consistently maintained aneuploidy of specific chromosomes over many generations. We investigated whether the persistence of these additional chromosomes in bub3 Δ cells resulted from the beneficial elevated expression of certain genes, or mere tolerance. We identified several genes involved in chromosome segregation and cell cycle regulation that confer an advantage to Bub3-depleted cells. Overall, our results suggest that the upregulation of specific genes through aneuploidy may provide a survival and growth advantage to strains with poor chromosome segregation fidelity.

AUTHOR SUMMARY

Accurate chromosome segregation is crucial for the proper development of all living organisms. Errors in chromosome segregation can lead to aneuploidy, characterized by an abnormal number of chromosomes, which generally impairs cell survival and growth. However, under certain stress conditions, such as in various cancers, cells with specific mutations and extra copies of advantageous chromosomes exhibit improved survival and proliferation. In our study, we discovered that cells lacking the spindle checkpoint protein Bub3 became aneuploid, retaining specific chromosomes. This finding was unexpected because although bub3 Δ cells have a higher rate of chromosome mis-segregation, they were not thought to maintain an aneuploid karyotype. We investigated whether the increased copy number of specific genes on these acquired chromosomes offered a benefit to Bub3-deficient cells. Our results revealed that several genes involved in chromosome segregation and cell cycle regulation prevented the gain of chromosomes upon Bub3-depletion, suggesting that these genes confer a survival advantage. Overall, our study demonstrates that cells lacking Bub3 selectively retain specific chromosomes to increase the copy number of genes that promote proper chromosome segregation.
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