Taschner Natalia Pasternak, Yagil Ezra, Spira Beny
Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Av. Prof. Lineu Prestes 1374, CEP 05508-900, São Paulo, Brazil.
Arch Microbiol. 2006 Apr;185(3):234-7. doi: 10.1007/s00203-005-0082-4. Epub 2006 Jan 11.
The pst operon, a member of the PHO regulon of Escherichia coli, encodes a high-affinity phosphate transport system whose expression is induced when the cells enter a phase of phosphate starvation. The expression of pst is stimulated by the integration host factor (IHF). Transcription of the PHO regulon genes is initiated by the RNA polymerase complexed with sigma (D) (Esigma (D)). Owing to a cytosine residue at position -13 of the pst promoter its transcription can also be initiated by Esigma (S). Here, we show that inactivation of IHF in vivo abolishes the sigma (S)-dependent transcription initiation of the pst operon, indicating that both -13C residue and IHF are required to confer on pst the ability to be transcribed by Esigma (S). Introduction of a -13C residue in the promoter region of phoA, another PHO regulon gene that is not directly affected by IHF, did not affect its exclusive transcription initiation by Esigma (D).
pst操纵子是大肠杆菌PHO调节子的成员，编码一种高亲和力的磷酸盐转运系统，当细胞进入磷酸盐饥饿阶段时其表达被诱导。pst的表达受整合宿主因子（IHF）刺激。PHO调节子基因的转录由与σ（D）复合的RNA聚合酶（Esigma（D））起始。由于pst启动子-13位的胞嘧啶残基，其转录也可由Esigma（S）起始。在此，我们表明体内IHF失活消除了pst操纵子的σ（S）依赖性转录起始，这表明-13C残基和IHF都是赋予pst被Esigma（S）转录能力所必需的。在phoA（另一个不受IHF直接影响的PHO调节子基因）的启动子区域引入-13C残基，并不影响其由Esigma（D）进行的唯一转录起始。
