The typical eukaryote interphase nuclei were reconstructed in vitro following incubation of chromosomes of primitive eukaryote dinoflagellate Crypthecodinium cohnii E. in extracts of S phase eggs of Xenopus laevis L. Micrococcal nuclease digestion experiments indicated that the reconstructed nuclei contained typical nucleosomes. Since the chromosomes of C. cohnii do not contain histone and nucleosomes, these data suggest that nucleosome assembly is independent of specific DNA sequences, nuclear membranes and Lamin. Moreover, it has been demonstrated that Topoisomerase Ⅱ was partially involved in the process of nucleosome assembly. Taken together, these findings suggest that nuclear assembly is independent of formation of nucleosomes and that histone and non-histone may be the decisive factors in this process.
甲藻染色体在非细胞体系核重建过程中核小体的组装
刘晓玲 陶伟 高云飞 卢智刚 翟中和*
（北京大学生命科学学院，北京100871）
摘要：利用纯化的原始真核生物寇氏隐甲藻（Crypthecodinium cohnii E.）染色体，使之与非洲爪蟾（Xenopus laevis L.）S期卵提取物温育，发现甲藻染色体经历了一系列去凝集、再凝集的形态变化，最后形成类似典型高等真核生物的间期核结构。小球菌核酸酶酶切分析表明，不具备组蛋白和核小体结构的甲藻染色体在非洲爪蟾卵提取物中进行了核小体装配，此过程与DNA序列本身、核膜以及核纤层蛋白（Lamin）是否存在无关，但部分拓扑异构酶Ⅱ（TopoⅡ）参与了这个过程，说明核小体的组装并非为核重建所必需，决定染色体高级结构的因素并不在DNA本身，而可能是非细胞体系中的组蛋白和非组蛋白。
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