Visualization of early chromosome condensation: a hierarchical folding, axial glue model of chromosome structure
Visualization of early chromosome condensation: a hierarchical folding, axial glue model of chromosome structure
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DOI：
10.1083/jcb.200406049
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发表时间：
2004-09-13
影响因子：
7.8
通讯作者：
Belmont, AS
中科院分区：
文献类型：
--
作者：
Kireeva, N;Lakonishok, M;Belmont, AS
当前的有丝分裂染色体结构模型主要基于对最大浓缩中期染色体的检查。在这里，我们通过将两个支架成分的分布与前期染色体折叠中间体的出现相关联来测试这些模型。我们确认了未提取的中期染色体中拓扑异构酶 IIα 和凝缩蛋白亚基的轴向分布，即 2 号染色体 (SMC2) 的结构维持，其中 SMC2 定位于直径 150-200 nm 的中央核心。与径向环/支架模型的预测相反，这种轴向分布直到前期后期、均匀压缩的中期前期染色体形成后才出现。相反，SMC2 与整个早期和中期前期染色单体结合，经常在染色体外部形成焦点。早期前期凝聚是通过将大规模染色质纤维折叠成凝聚团而发生的。它们分解成线性的、直径为 200-300 nm 的中期前期染色单体，到后期其直径加倍。我们提出了一个统一的染色体结构模型，其中染色质折叠的层次水平在有丝分裂后期通过轴向“胶水”得以稳定。
Current models of mitotic chromosome structure are based largely on the examination of maximally condensed metaphase chromosomes. Here, we test these models by correlating the distribution of two scaffold components with the appearance of prophase chromosome folding intermediates. We confirm an axial distribution of topoisomerase IIalpha and the condensin subunit, structural maintenance of chromosomes 2 (SMC2), in unextracted metaphase chromosomes, with SMC2 localizing to a 150-200-nm-diameter central core. In contrast to predictions of radial loop/scaffold models, this axial distribution does not appear until late prophase, after formation of uniformly condensed middle prophase chromosomes. Instead, SMC2 associates throughout early and middle prophase chromatids, frequently forming foci over the chromosome exterior. Early prophase condensation occurs through folding of large-scale chromatin fibers into condensed masses. These resolve into linear, 200-300-nm-diameter middle prophase chromatids that double in diameter by late prophase. We propose a unified model of chromosome structure in which hierarchical levels of chromatin folding are stabilized late in mitosis by an axial "glue".