Asai T, Chen C P, Nagata T, Takanami M, Imai M
Institute for Virus Research, Kyoto University, Japan.
Mol Gen Genet. 1992 Jan;231(2):169-78. doi: 10.1007/BF00279788.
Within the replication origin, oriC, of the Escherichia coli chromosome, novel in vivo transcripts were detected which proceeded rightward and whose production was activated by DnaA protein. In contrast, DnaA protein repressed the previously described ori-L leftward transcription. The former should introduce negative supercoiling, and the latter positive supercoiling, into the 13-mers. The effects of transcription on the initiation of replication were also investigated by making constructs with promoters placed near oriC. Transcription was found to enhance the origin activity only when it was oriented in such a way as to introduce negative supercoiling into the 13-mers. From these results, we propose that transcription within oriC regulates replication initiation by altering the topology of the 13-mer region.
在大肠杆菌染色体的复制起点oriC内，检测到了新的体内转录本，这些转录本向右进行，其产生由DnaA蛋白激活。相比之下，DnaA蛋白抑制了先前描述的ori-L向左转录。前者会在13聚体中引入负超螺旋，而后者会引入正超螺旋。还通过构建靠近oriC放置启动子的结构来研究转录对复制起始的影响。发现只有当转录以向13聚体中引入负超螺旋的方式定向时，转录才会增强起点活性。根据这些结果，我们提出oriC内的转录通过改变13聚体区域的拓扑结构来调节复制起始。
