Coleman T R, Carpenter P B, Dunphy W G
Division of Biology, Howard Hughes Medical Institute, California Institute of Technology, Pasadena 91125, USA.
Cell. 1996 Oct 4;87(1):53-63. doi: 10.1016/s0092-8674(00)81322-7.
We have cloned a Xenopus Cdc6 homolog (Xcdc6) and characterized its role in DNA replication with Xenopus egg extracts. Immunodepletion of Xcdc6 abolishes chromosomal replication but not elongation on single-stranded DNA templates. Xcdc6 binds to chromatin at the beginning of interphase but disappears from chromatin upon initiation of replication. Immunodepletion studies indicate that binding of Xcdc6 to chromatin requires Xorc2, a component of the origin recognition complex. Moreover, Xmcm3 cannot bind to chromatin lacking Xcdc6, suggesting that Xorc2, Xcdc6, and Xmcm3 associate with the DNA sequentially. In postreplicative nuclei, Xcdc6 is associated with the nuclear envelope. These studies indicate that Xcdc6, is essential for initiation of replication in vertebrates and that interaction with the nuclear envelope may regulate its function.
我们克隆了非洲爪蟾Cdc6同源物（Xcdc6），并利用非洲爪蟾卵提取物对其在DNA复制中的作用进行了表征。Xcdc6的免疫耗竭消除了染色体复制，但不影响单链DNA模板上的延伸。Xcdc6在间期开始时与染色质结合，但在复制起始时从染色质上消失。免疫耗竭研究表明，Xcdc6与染色质的结合需要Xorc2，即起始识别复合物的一个组分。此外，Xmcm3不能与缺乏Xcdc6的染色质结合，这表明Xorc2、Xcdc6和Xmcm3依次与DNA结合。在复制后细胞核中，Xcdc6与核膜相关。这些研究表明，Xcdc6对脊椎动物的复制起始至关重要，并且与核膜的相互作用可能调节其功能。
