SRA

Aneuploidy, a condition characterized by whole chromosome gains and losses, is often associated with significant cellular stress and decreased fitness. However, whether and how cells respond to the aneuploid state has remained controversial. In aneuploid budding yeast, two opposing gene expression patterns have been reported: an environmental stress response (ESR) and a “common aneuploidy gene-expression” (CAGE) signature, in which many ESR genes are oppositely regulated. Here, we investigate and bring clarity to this controversy. We show that the CAGE signature is not an aneuploidy-specific gene expression signature but is the result of euploid control cells, but not aneuploid cells, having grown into stationary phase. Because growth into stationary phase is amongst the strongest inducers of the ESR, the ESR in aneuploid cells was masked when stationary phase euploid cells were used for normalization in transcriptomic studies. When exponentially growing euploid cells are used in gene expression comparisons with aneuploid cells, the CAGE signature is no longer evident in aneuploid cells. Instead, aneuploid cells are found to exhibit the ESR. We further show that the ESR causes a selective loss of ribosomes in aneuploid cells, providing an explanation for the decreased cellular density in aneuploid cells. We conclude that aneuploid budding yeast cells mount the ESR, rather than a CAGE signature, in response to aneuploidy-induced cellular stresses that results in selective ribosome loss. Overall design: Examination of gene expression signatures in euploid and aneuploid yeast strains under different growth conditions.