Hopper S, Babst M, Schlensog V, Fischer H M, Hennecke H, Böck A
Lehrstuhl für Mikrobiologie der Universität München, Germany.
J Biol Chem. 1994 Jul 29;269(30):19597-604.
Purified FHLA, the transcriptional activator of the formate regulon from Escherichia coli, is able to efficiently stimulate transcription from the sigma 54-dependent promoters of the fdhF, hyp, and hyc transcriptional units. Expression was dependent on the presence of sigma 54, of the upstream activatory sequence (UAS), and of formate. Hypophosphite, a formate analogue, could substitute for formate in vitro suggesting that formate per se was active in regulation. The integration host factor (IHF) had a direct effect on the expression (in vivo and in vitro) of the hyp and hyc genes but not of the fdhF gene. Binding of IHF within the region between the hyp and the hyc operon could be shown. A model is proposed for the transcriptional regulation of the inversely oriented hyp and hyc operons. It involves two upstream regulatory sequences, one between the hyp and the hyc operon (IR1), and the other between hycA and hycB (IR2). The UAS situated within IR1 is responsible for activation of the hyc operon, that within IR2 for activation of the hyp operon. A supramolecular transcription complex is proposed which involves the binding of IHF to a site located between the UAS and the promoter responsible for transcription of the hyc operon.
纯化的FHLA是来自大肠杆菌甲酸操纵子的转录激活因子，能够有效刺激fdhF、hyp和hyc转录单元中依赖σ⁵⁴的启动子的转录。表达依赖于σ⁵⁴、上游激活序列（UAS）和甲酸的存在。次磷酸盐是一种甲酸类似物，在体外可替代甲酸，这表明甲酸本身在调控中具有活性。整合宿主因子（IHF）对hyp和hyc基因的表达（体内和体外）有直接影响，但对fdhF基因没有影响。可以证明IHF在hyp和hyc操纵子之间的区域内结合。提出了一个关于反向排列的hyp和hyc操纵子转录调控的模型。它涉及两个上游调控序列，一个在hyp和hyc操纵子之间（IR1），另一个在hycA和hycB之间（IR2）。位于IR1内的UAS负责激活hyc操纵子，位于IR2内的UAS负责激活hyp操纵子。提出了一种超分子转录复合体，它涉及IHF与位于UAS和负责hyc操纵子转录的启动子之间的一个位点的结合。
