Mitotic chromosome condensation resets chromatin to maintain post-anaphase transcriptional homeostasis (RNA-Seq III)

Mitotic entry correlates with remodeling of histone modifications, chromatin condensation, exclusion of transcription factors from the DNA and broad downregulation of transcription. However, whether mitotic condensation also influences interphase transcription is a question that has not been addressed yet. In this study, we reveal that loss of mitotic chromatin condensation results in a dramatic and spontaneous recruitment of the transcription machinery and unscheduled initiation of gene expression. This includes activation of inducible transcriptional programs, which occurs even in absence of relevant stimuli, such as the GAL system. Strikingly, such an erratic gene expression goes on after exit from mitosis. Thus, we reveal a novel function of mitotic chromosome condensation, i.e. resetting the transcriptome to prevent gene expression from drifting and maintain transcriptional homeostasis during interphase.细胞进入有丝分裂（Mitotic entry）时，会伴随组蛋白修饰（histone modifications）重塑、染色质凝聚（chromatin condensation）、转录因子（transcription factors）被排除出DNA，以及转录水平的广泛下调。然而，有丝分裂凝聚是否也会影响间期转录（interphase transcription），这一科学问题迄今尚未得到解答。本研究表明，有丝分裂染色质凝聚（mitotic chromatin condensation）的缺失会导致转录机器（transcription machinery）发生显著且自发性的募集，并引发异常的基因表达起始（unscheduled initiation of gene expression）。这一过程包括可诱导转录程序（inducible transcriptional programs）的激活，即便在缺乏相关刺激（如GAL系统（GAL system））的情况下也会发生。值得注意的是，这种异常的基因表达会在有丝分裂退出后持续存在。综上，我们揭示了有丝分裂染色体凝聚（mitotic chromosome condensation）的一项全新功能：重置转录组（transcriptome），以防止基因表达出现异常漂移，并在间期维持转录稳态（transcriptional homeostasis）。