Mitotic chromosome condensation resets chromatin to safeguard transcriptional homeostasis during interphase

Mitotic entry correlates with the condensation of the chromosomes, changes in histone modifications, exclusion of transcription factors from DNA, and the broad downregulation of transcription. However, whether mitotic condensation influences transcription in the subsequent interphase is unknown. Here, we show that preventing one chromosome to condense during mitosis causes it to fail resetting of transcription. Rather, in the following interphase, the affected chromosome contains unusually high levels of the transcription machinery, resulting in abnormally high expression levels of genes in cis, including various transcription factors. This subsequently causes the activation of inducible transcriptional programs in trans, such as the GAL genes, even in the absence of the relevant stimuli. Thus, mitotic chromosome condensation exerts stringent control on interphase gene expression to ensure the maintenance of basic cellular functions and cell identity across cell divisions. Together, our study identifies the maintenance of transcriptional homeostasis during interphase as an unexpected function of mitosis and mitotic chromosome condensation.

Automated summary

Mitotic entry is associated with a series of cellular changes in chromosomes and transcription factors, leading to downregulation of transcription. However, the influence of mitotic condensation on transcription during interphase is unknown. In this study, we found that failure to condense a specific chromosome during mitosis resulted in aberrant transcription in the subsequent interphase, leading to high expression levels of genes in cis and the activation of inducible transcriptional programs in trans. These findings reveal an unexpected role of mitosis and mitotic chromosome condensation in maintaining transcriptional homeostasis during interphase.