Göransson M, Forsman P, Nilsson P, Uhlin B E
Department of Microbiology, University of Umeå, Sweden.
Mol Microbiol. 1989 Nov;3(11):1557-65. doi: 10.1111/j.1365-2958.1989.tb00141.x.
Transcription of the genes encoding pilus-adhesin of serotype F13 in digalactoside-binding Escherichia coli required activation by the cAMP-CRP complex. Analysis of protein-DNA interaction in vitro showed that CRP bound in a cAMP-dependent manner to a sequence located 0.2 kb upstream of the point of transcription initiation of the pilus subunit operon. The cAMP-CRP activation included, in addition to the main pilus operon, the oppositely oriented operon encoding the Papl regulatory protein. Furthermore, the auto-regulatory product of the promoter-proximal gene (papB) in the pilus subunit operon was found to stimulate the papl transcriptional unit. Thus the cAMP-CRP complex and PapB might act in concert and indirectly promote pili synthesis by stimulating expression of the Papl positive regulator. The results of trans-complementation experiments and analyses using lacZ operon fusion derivatives showed that the cAMP-CRP activation also operated directly in cis on the pilus subunit operon. The region containing the CRP binding site appeared to function as an upstream activating sequence since deletion abolished expression even when the pap regulatory proteins Papl and PapB were supplied in trans. The implications for possible mechanisms of transcriptional activation by the cAMP-CRP complex at this novel location between the two oppositely oriented operons are discussed.
在半乳糖苷结合型大肠杆菌中，血清型F13菌毛黏附素编码基因的转录需要cAMP - CRP复合物的激活。体外蛋白质 - DNA相互作用分析表明，CRP以cAMP依赖的方式结合到菌毛亚基操纵子转录起始点上游0.2 kb处的一个序列上。cAMP - CRP的激活作用除了作用于主要的菌毛操纵子外，还包括作用于编码Papl调节蛋白的反向操纵子。此外，发现菌毛亚基操纵子中启动子近端基因（papB）的自调控产物能刺激papl转录单元。因此，cAMP - CRP复合物和PapB可能协同作用，通过刺激Papl正调控因子的表达间接促进菌毛合成。反式互补实验结果以及使用lacZ操纵子融合衍生物的分析表明，cAMP - CRP的激活作用也直接顺式作用于菌毛亚基操纵子。包含CRP结合位点的区域似乎起到上游激活序列的作用，因为即使反式提供菌毛调节蛋白Papl和PapB，缺失该区域也会导致表达缺失。本文讨论了cAMP - CRP复合物在这两个反向操纵子之间的新位置上进行转录激活的可能机制。
