在有丝分裂期间,凝缩素活性被认为会干扰相间染色质结构。为了研究在没有染色质环挤出的情况下的基因组折叠原理,我们编码了凝析素I和凝析素II,以类似于间期的方式触发有丝分裂染色体区隔。然而,两个不同的常色隔室,在相间无法区分,凝析素损失时出现,具有不同的相互作用偏好和对H3K27ac的依赖性。组成性异染色质逐渐自聚集并与兼性异染色质共同分隔,与它们在相间的分离形成对比。值得注意的是,即使没有CTCF/粘附素介导的结构,一些顺式调控元件接触也变得明显.异染色质蛋白1(HP1)蛋白,它们被认为是划分组成性异染色质的,从有丝分裂染色体中缺失,暗示,令人惊讶的是,组成型异染色质可以在没有HP1的情况下自我聚集。的确,在合并不存在HP1α的情况下,从M到G1期的细胞中,HP1β和HP1γ,组成性异染色质区室通常会重新建立。总之,凝缩素缺陷的有丝分裂染色体阐明了在间期细胞中未发现的基因组区室化的力量。
During mitosis, condensin activity is thought to interfere with interphase chromatin structures. To investigate genome folding principles in the absence of chromatin loop extrusion, we codepleted condensin I and condensin II, which triggered mitotic chromosome compartmentalization in ways similar to that in interphase. However, two distinct euchromatic compartments, indistinguishable in interphase, emerged upon condensin loss with different interaction preferences and dependencies on H3K27ac. Constitutive
heterochromatin gradually self-aggregated and cocompartmentalized with facultative
heterochromatin, contrasting with their separation during interphase. Notably, some cis-regulatory element contacts became apparent even in the absence of CTCF/cohesin-mediated structures.
Heterochromatin protein 1 (HP1) proteins, which are thought to partition constitutive
heterochromatin, were absent from mitotic chromosomes, suggesting, surprisingly, that constitutive
heterochromatin can self-aggregate without HP1. Indeed, in cells traversing from M to G1 phase in the combined absence of HP1α, HP1β and HP1γ, constitutive
heterochromatin compartments are normally re-established. In sum, condensin-deficient mitotic chromosomes illuminate forces of genome compartmentalization not identified in interphase cells.