Dual roles of the 11S regulatory subcomplex in condensin functions
Dual roles of the 11S regulatory subcomplex in condensin functions
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DOI：
10.1073/pnas.220326097
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发表时间：
2000-10-24
影响因子：
11.1
通讯作者：
Hirano, T
中科院分区：
文献类型：
--
作者：
Kimura, K;Hirano, T
凝缩蛋白是一种多亚基蛋白质复合物，它在体外以依赖ATP的方式重构DNA结构，并在非洲爪蟾无细胞卵提取物的有丝分裂染色体凝缩中起核心作用。非洲爪蟾13S凝缩蛋白复合物（13SC）由两个亚复合物组成：一个8S核心亚复合物（8SC），由两个染色体结构维持（SMC）亚基（XCAP - C和 - E）组成；一个11S调节亚复合物（11SR），包含三个非SMC亚基（XCAP - D2、 - G和 - H）。我们在此报告这种染色体凝缩机制的生化和功能解析。尽管8SC和13SC在体外都能与DNA结合且都包含SMC ATP酶亚基，但只有13SC作为一种DNA刺激的ATP酶具有活性，并支持依赖ATP的超螺旋活性。在无细胞提取物中，13SC是与染色体结合并诱导其凝缩的活性形式。11SR或8SC单独都不能与染色质结合。我们的结果表明，非SMC亚基在凝缩蛋白功能的调节中具有双重作用：一个是激活SMC ATP酶，另一个是以一种有丝分裂特异性的方式使全复合物与染色质结合。
Condensin is a multisubunit protein complex that reconfigures DNA structure in an ATP-dependent manner in vitro and plays a central role in mitotic chromosome condensation in Xenopus egg cell-free extracts. The Xenopus 13S condensin complex (13SC) is composed of two subcomplexes: an 8S core subcomplex (8SC) consisting of two structural maintenance of chromosomes (SMC) subunits (XCAP-C and -E) and an 11S regulatory subcomplex (11SR) containing three non-SMC subunits (XCAP-D2, -G, and -H). We report here the biochemical and functional dissection of this chromosome condensation machinery. Although both 8SC and 13SC can bind to DNA in vitro and contain the SMC ATPase subunits,only 13SC is active as a DNA-stimulated ATPase and supports ATP-dependent supercoiling activity. In the cell-free extracts, 13SC is the active form that binds to chromosomes and induces their condensation. Neither 11SR nor 8SC alone is able to bind to chromatin. Our results suggest that the non-SMC subunits have dual roles in the regulation of condensin functions: one is to activate SMC ATPases and the other is to allow the holocomplex to associate with chromatin in a mitosis-specific manner.