Coverley D, Wilkinson H R, Madine M A, Mills A D, Laskey R A
Department of Zoology, University of Cambridge, United Kingdom.
Exp Cell Res. 1998 Jan 10;238(1):63-9. doi: 10.1006/excr.1997.3829.
Intact nuclei from G2-phase mammalian cells will replicate their DNA in Xenopus egg extract if they are preexposed to the protein kinase inhibitor 6-dimethylaminopurine in vivo (Coverley et al., Exp. Cell Res. 225, 294-300, 1996). Here, we demonstrate that this competence to rereplicate is accompanied by alterations in the subcellular distribution of the Mcm family of proteins, which are implicated in replication licensing (Hennessy et al., Genes Dev. 4, 2252-2263, 1990; Kubota et al., Cell 81, 601-609, 1995; and Chong et al., Nature 375, 418-421, 1995). All family members reassociate with chromatin in G2 cells and this correlates closely with regeneration of replication competence. Moreover, newly bound Mcm proteins are functional for replication because, unlike untreated G2 nuclei, replication of treated G2 nuclei in vitro occurs independent of the Xenopus Mcm protein complex. These observations show that the postreplicative state is actively maintained in G2 cells by a protein kinase(s) which regulates the behavior of Mcm family proteins.
如果来自G2期哺乳动物细胞的完整细胞核在体内预先暴露于蛋白激酶抑制剂6 - 二甲基氨基嘌呤，那么它们将在非洲爪蟾卵提取物中复制其DNA（Coverley等人，《实验细胞研究》225，294 - 300，1996）。在此，我们证明这种重新复制的能力伴随着Mcm蛋白家族亚细胞分布的改变，而Mcm蛋白家族与复制许可有关（Hennessy等人，《基因与发育》4，2252 - 2263，1990；Kubota等人，《细胞》81，601 - 609，1995；以及Chong等人，《自然》375，418 - 421，1995）。所有家族成员在G2期细胞中与染色质重新结合，这与复制能力的恢复密切相关。此外，新结合的Mcm蛋白对复制具有功能，因为与未处理的G2期细胞核不同，体外处理过的G2期细胞核的复制独立于非洲爪蟾Mcm蛋白复合物发生。这些观察结果表明，G2期细胞中的复制后状态通过一种调节Mcm蛋白家族行为的蛋白激酶被积极维持。
