Krevolin M D, Inman R B, Roof D, Kahn M, Calendar R
J Mol Biol. 1985 Apr 20;182(4):519-27. doi: 10.1016/0022-2836(85)90238-4.
An electron microscopic examination of replicating bacteriophage P4 DNA molecules has revealed theta-type structures that replicate bidirectionally from a single origin. Many replicating P4 DNA molecules also contain long (2000 bases) single-strand DNA regions at the growing fork that are deployed in a trans configuration, which supports the concept of continuous leading strand and discontinuous lagging strand syntheses. The position of the P4 origin was localized by the use of a plasmid complementation test for replication in vivo, as well as by labeling of DNA replicating in vitro in the presence of a chain-terminating inhibitor. During this study we discovered a second site on the P4 genome which is essential for replication, and we have named it crr (cis region required for replication). The site is located at least 3300 bases from the origin but appears to be required for the initiation of DNA replication in vivo as well as in vitro.
对正在复制的噬菌体P4 DNA分子进行的电子显微镜检查揭示了theta型结构，其从单一原点双向复制。许多正在复制的P4 DNA分子在生长叉处还含有长（2000个碱基）的单链DNA区域，这些区域以反式构型分布，这支持了连续前导链和不连续滞后链合成的概念。通过使用质粒互补试验在体内进行复制定位P4原点的位置，并通过在链终止抑制剂存在的情况下标记体外复制的DNA来定位。在这项研究中，我们在P4基因组上发现了第二个对复制至关重要的位点，我们将其命名为crr（复制所需的顺式区域）。该位点距离原点至少3300个碱基，但似乎是体内和体外DNA复制起始所必需的。
