Distribution of condensins and chromosome architecture

真核细胞具有两种不同的凝缩蛋白复合物，称为凝缩蛋白I和凝缩蛋白II。两者在有丝分裂染色体的组装和分离过程中都起着重要而不同的作用。有趣的是，凝缩蛋白II倾向于在g波段区域富集。人们早就知道g带区域在S期复制较晚，在前期凝结较早。这组信息允许我们提出一个工作假设，即凝聚素II可能在连接S期DNA复制和M期染色体凝聚中发挥作用。定量细胞成像分析结合免疫染色显示凝缩蛋白II在S期开始与染色体结合。有趣的是，在存在复制胁迫的情况下，凝缩蛋白II的耗竭而不是凝缩蛋白I的耗竭导致了染色体在M期的关键异常。这些结果表明，凝聚素II可能在S期复制染色体的结构转化中起关键作用，从而促进染色体在M期的凝聚。

Eukaryotic cells possess two different condensin complexes, known as condensin I and II. Both play essential yet distinct functions in the processes of mitotic chromosome assembly and segregation. Interestingly, condensin II tends to be enriched in G-band regions. It has long been known that G-band regions are replicated later in S phase and condense earlier in prophase. This set of information allows us to propose the working hypothesis that condensin II may play a role in linking DNA replication in S phase to chromosome condensation in M phase. Quantitative cell imaging analyses combined with immunostaining show that condensin II start to associate with chromosomes during S phase. Interestingly, in the presence of replication stress, the depletion of condensin II, but not of condensin I, induced a critical abnormality in chromosome in M phase. These results suggest that condensin II may play a crucial role in structural conversion of replicated chromosomes during S phase to facilitate chromosome condensation in M phase.