Natarajan S, Kelley W L, Bastia D
Department of Microbiology and Immunology, Duke University Medical Center, Durham, NC 27710.
Proc Natl Acad Sci U S A. 1991 May 1;88(9):3867-71. doi: 10.1073/pnas.88.9.3867.
We have investigated the regulation of synthesis of the replication terminator protein (Ter) of Escherichia coli and have discovered that the protein is a repressor of its own synthesis at the transcriptional step. Since the synthesis of Ter protein was observed to be down-regulated in vivo, these results are consistent with autoregulation as one control mechanism of Ter protein within the cell. Analysis of the tus gene that encodes the Ter protein revealed that transcription was initiated from a single promoter located within the upstream nontranscribed sequence. In vitro footprinting experiments have revealed that Ter protein prevented binding of RNA polymerase to the promoter sequence when both proteins were incubated with promoter DNA. However, once bound to the promoter, RNA polymerase could not be displaced by Ter protein. Conversely, prebound Ter protein could not be dislodged from its binding site at the promoter when challenged with RNA polymerase. Therefore, Ter protein can serve as a transcriptional repressor of its own synthesis by preventing RNA polymerase from binding to the tus promoter when both proteins are present in the cell milieu.
我们研究了大肠杆菌复制终止蛋白（Ter）合成的调控机制，发现该蛋白在转录水平上是其自身合成的阻遏物。由于在体内观察到Ter蛋白的合成受到下调，这些结果与自动调节作为细胞内Ter蛋白的一种控制机制是一致的。对编码Ter蛋白的tus基因的分析表明，转录起始于位于上游非转录序列内的单个启动子。体外足迹实验表明，当Ter蛋白与启动子DNA一起孵育时，它会阻止RNA聚合酶与启动子序列结合。然而，一旦RNA聚合酶与启动子结合，Ter蛋白就无法将其取代。相反，当受到RNA聚合酶的挑战时，预先结合在启动子上的Ter蛋白无法从其结合位点上被移除。因此，当细胞环境中同时存在这两种蛋白时，Ter蛋白可以通过阻止RNA聚合酶与tus启动子结合，作为其自身合成的转录阻遏物。
