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

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.细胞进入有丝分裂的过程，伴随组蛋白修饰重塑、染色质浓缩、转录因子从DNA上被排除，以及转录的广泛下调。然而，有丝分裂浓缩是否同样会影响间期转录，这一问题至今尚未得到解答。本研究发现，有丝分裂染色质浓缩的缺失，会导致转录机器被显著且自发性地招募，并引发基因表达的异常起始。这其中包括可诱导转录程序的激活——即使在缺乏相关刺激（如GAL系统）的条件下，该激活过程仍可发生。值得注意的是，这种异常的基因表达会在细胞退出有丝分裂后仍持续存在。据此，本研究揭示了有丝分裂染色体浓缩的一项全新功能：重置转录组，以防止间期内基因表达发生紊乱，并维持转录稳态。