Guggenheimer R A, Nagata K, Kenny M, Hurwitz J
J Biol Chem. 1984 Jun 25;259(12):7815-25.
A host protein, which is required for the replication of a plasmid DNA (pLA1), has been purified from extracts of uninfected HeLa nuclei. This plasmid DNA contains the origin of adenovirus DNA replication but lacks the 55,000-dalton terminal proteins. The purified host protein has been designated factor pL. Factor pL is essential for the initiation of DNA replication of EcoRI-digested pLA1 DNA, which proceeds via the formation of a covalent complex between the 80,000-dalton adenovirus coded preterminal protein and 5' dCMP. Factor pL has been purified approximately 120-fold to greater than 75% homogeneity. It is a heat labile and N-ethylmaleimide-sensitive protein with a native Mr = 39,000 (+/- 2,000). Initiation of DNA replication using EcoRI-digested pLA1 DNA as the template requires the 80,000-dalton preterminal protein and the 140,000-dalton adenovirus DNA polymerase, in addition to factor pL, and is stimulated as much as 10-fold by nuclear factor I ( Nagata , K., Guggenheimer , R. A., Enomoto , T., Lichy , J. H., and Hurwitz , J. (1982) Proc. Natl. Acad. Sci. U. S. A. 79, 6438-6442). Factor pL has no effect on in vitro DNA replication when adenovirus DNA covalently linked to the 55,000-dalton terminal protein is used as the template, however the replication of adenovirus DNA treated with Pronase, becomes totally dependent upon the addition of factor pL.
一种宿主蛋白已从未感染的HeLa细胞核提取物中纯化出来，该蛋白是质粒DNA（pLA1）复制所必需的。这种质粒DNA含有腺病毒DNA复制起点，但缺乏55,000道尔顿的末端蛋白。纯化的宿主蛋白被命名为因子pL。因子pL对于经EcoRI酶切的pLA1 DNA的DNA复制起始至关重要，该复制过程通过80,000道尔顿的腺病毒编码前末端蛋白与5'-dCMP之间形成共价复合物来进行。因子pL已被纯化约120倍，纯度超过75%。它是一种对热不稳定且对N-乙基马来酰亚胺敏感的蛋白，天然分子量为39,000（±2,000）。以经EcoRI酶切的pLA1 DNA为模板进行DNA复制起始，除了因子pL外，还需要80,000道尔顿的前末端蛋白和140,000道尔顿的腺病毒DNA聚合酶，并且受到核因子I的刺激可达10倍之多（永田，K.，古根海默，R.A.，榎本，T.，利奇，J.H.，和赫维茨，J.（1982年）美国国家科学院院刊79，6438 - 6442）。当以与55,000道尔顿末端蛋白共价连接的腺病毒DNA为模板时，因子pL对体外DNA复制没有影响，然而，经链霉蛋白酶处理的腺病毒DNA的复制则完全依赖于因子pL的添加。
