Coué M, Amariglio F, Maiorano D, Bocquet S, Méchali M
Institut Jacques Monod, CNRS, Université Paris 7, 2 place Jussieu, Paris Cedex 05, 75251, France.
Exp Cell Res. 1998 Dec 15;245(2):282-9. doi: 10.1006/excr.1998.4271.
MCM proteins are molecular components of the DNA replication licensing system in Xenopus. These proteins comprise a conserved family made up of six distinct members which have been found to associate in large protein complexes. We have used a combination of biochemical and cytological methods to study the association of soluble and chromatin-bound Xenopus MCM proteins during the cell cycle. In interphase, soluble MCM proteins are found organized in a core salt-resistant subcomplex that includes MCM subunits which are known to have high affinity for histones. The interphasic complex is modified at mitosis and the subunit composition of the resulting mitotic subcomplexes is distinct, indicating that the stability of the MCM complex is under cell cycle control. Moreover, we provide evidence that the binding of MCM proteins to chromatin may occur in sequential steps involving the loading of distinct MCM subunits. Comparative analysis of the chromatin distribution of MCM2, 3, and 4 shows that the binding of MCM4 is distinct from that of MCM2 and 3. Altogether, these data suggest that licensing of chromatin by MCMs occurs in an ordered fashion involving discrete subcomplexes.
MCM蛋白是非洲爪蟾DNA复制许可系统的分子组成部分。这些蛋白构成了一个保守家族，由六个不同成员组成，已发现它们能结合形成大型蛋白质复合物。我们结合生化和细胞学方法，研究了非洲爪蟾MCM蛋白在细胞周期中可溶性形式与染色质结合形式的关联。在间期，可溶性MCM蛋白以一种核心抗盐亚复合物的形式存在，该亚复合物包含已知对组蛋白具有高亲和力的MCM亚基。间期复合物在有丝分裂时发生修饰，产生的有丝分裂亚复合物的亚基组成不同，这表明MCM复合物的稳定性受细胞周期调控。此外，我们提供证据表明，MCM蛋白与染色质的结合可能按顺序步骤发生，涉及不同MCM亚基的加载。对MCM2、3和4染色质分布的比较分析表明，MCM4的结合与MCM2和3不同。总之，这些数据表明，MCM对染色质的许可以有序方式发生，涉及离散的亚复合物。
