Murphree D, Froehlich B, Scott J R
Department of Microbiology and Immunology, Emory University, Atlanta, Georgia 30322, USA.
J Bacteriol. 1997 Sep;179(18):5736-43. doi: 10.1128/jb.179.18.5736-5743.1997.
The adherence of enterotoxigenic Escherichia coli (ETEC) to the human small intestine is an important early event in infection. Attachment is thought to be mediated by proteinaceous structures called pili. We have investigated the regulation of expression of the genes encoding CS1 pili found on human ETEC strains and find that there are at least three promoters, P1 and P2, upstream of the coo genes, and P3, downstream of the start of cooB translation. We identified a silencer of transcription which extends over several hundred bases overlapping the cooB open reading frame. This silencer is dependent on the promoter and/or upstream region for its negative effect. The DNA binding protein H-NS is a repressor of coo transcription that acts in the same region as the silencer, so it is possible that H-NS is involved in this silencing. Rns, a member of the AraC family, positively regulates transcription of the coo operon and relieves the silencing of CS1 expression.
产肠毒素大肠杆菌（ETEC）对人类小肠的黏附是感染过程中重要的早期事件。据认为，黏附是由称为菌毛的蛋白质结构介导的。我们研究了人类ETEC菌株上编码CS1菌毛的基因表达调控，发现coo基因上游至少有三个启动子，即P1和P2，以及cooB翻译起始位点下游的P3。我们鉴定出一个转录沉默子，其延伸数百个碱基，与cooB开放阅读框重叠。该沉默子的负效应依赖于启动子和/或上游区域。DNA结合蛋白H-NS是coo转录的阻遏物，作用于与沉默子相同的区域，因此H-NS有可能参与这种沉默作用。AraC家族成员Rns对coo操纵子的转录起正调控作用，并解除CS1表达的沉默。
