Frappier L, O'Donnell M
Howard Hughes Medical Institute, Microbiology Department, Cornell University Medical College, New York, NY 10021.
Proc Natl Acad Sci U S A. 1991 Dec 1;88(23):10875-9. doi: 10.1073/pnas.88.23.10875.
Epstein-Barr virus-encoded nuclear antigen 1 (EBNA-1) binds and activates the viral latent origin of DNA replication, oriP. We have used electron microscopy to examine the assembly of EBNA-1 onto oriP. The oriP region consists of two essential elements separated by approximately 1 kilobase pair of DNA. One element contains 20 tandom EBNA-1 binding sites [called the family of repeats (FR)] and serves to activate initiation of replication at the dyad symmetry (DS) element, which contains 4 EBNA-1 binding sites. Titration of homogeneous EBNA-1 produced in baculovirus (bEBNA-1) onto oriP DNA showed an order to the assembly of bEBNA-1 onto oriP. At low concentrations, bEBNA-1 was located exclusively on the FR element. As the level of bEBNA-1 was raised, a loop between the FR and DS elements became the most prevalent DNA-protein complex. These data suggest protein-mediated DNA looping may play a role in activating latent-phase replication of the Epstein-Barr virus.
爱泼斯坦-巴尔病毒编码的核抗原1（EBNA-1）结合并激活病毒DNA复制的潜伏起始位点oriP。我们利用电子显微镜来研究EBNA-1在oriP上的组装情况。oriP区域由两个必需元件组成，它们被大约1千碱基对的DNA隔开。一个元件包含20个串联的EBNA-1结合位点[称为重复序列家族（FR）]，并用于激活在包含4个EBNA-1结合位点的双对称（DS）元件处的复制起始。将杆状病毒中产生的同源EBNA-1（bEBNA-1）滴定到oriP DNA上，显示出bEBNA-1在oriP上的组装顺序。在低浓度时，bEBNA-1仅位于FR元件上。随着bEBNA-1水平的升高，FR和DS元件之间的一个环成为最普遍的DNA-蛋白质复合物。这些数据表明蛋白质介导的DNA环化可能在激活爱泼斯坦-巴尔病毒的潜伏相复制中起作用。
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