Zavitz K H, Marians K J
Program in Molecular Biology, Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
Mol Microbiol. 1991 Dec;5(12):2869-73. doi: 10.1111/j.1365-2958.1991.tb01846.x.
The multi-functional PriA protein of Escherichia coli (formerly replication factor Y or protein n') serves to guide the ordered assembly of the primosome, a mobile multiprotein replication priming/helicase complex. Primosome assembly is essential for bacteriophage OX174 complementary DNA strand synthesis and ColE1-type plasmid replication reconstituted in vitro with purified proteins. The biochemical activities of the primosome suggest that it can fulfill the primase/helicase requirement on the lagging-strand DNA template during cellular DNA replication. However, reconstruction in vitro of DNA replication of small plasmids containing the E. coli origin of DNA replication (oriC) does not require the complete complement of primosomal proteins. Thus, the extent to which PriA-catalysed primosome assembly participates in chromosomal replication has remained unclear. The recent isolation of the genes encoding PriA, PriB (protein n), PriC (protein n"), and DnaT (protein i) has provided the necessary tools for addressing this issue. The phenotype of mutations in these genes, and other results described in this review, suggest that assembly of the primosome catalysed by PriA does in fact contribute at some stage to normal cellular DNA replication. A model for primososme-catalysed reactivation of a dysfunctional replication fork is discussed.
大肠杆菌的多功能PriA蛋白（以前称为复制因子Y或蛋白n'）用于引导引发体的有序组装，引发体是一种移动的多蛋白复制引发/解旋酶复合物。引发体组装对于噬菌体OX174互补DNA链合成以及用纯化蛋白在体外重建的ColE1型质粒复制至关重要。引发体的生化活性表明，它可以在细胞DNA复制过程中满足滞后链DNA模板上对引发酶/解旋酶的需求。然而，体外重建含有大肠杆菌DNA复制起点（oriC）的小质粒的DNA复制并不需要引发体蛋白的完整补充。因此，PriA催化的引发体组装在染色体复制中参与的程度仍不清楚。最近分离出编码PriA、PriB（蛋白n）、PriC（蛋白n"）和DnaT（蛋白i）的基因，为解决这个问题提供了必要的工具。这些基因中的突变表型以及本综述中描述的其他结果表明，PriA催化的引发体组装实际上在某个阶段对正常细胞DNA复制有贡献。本文讨论了引发体催化功能失调的复制叉重新激活的模型。
