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Activation of a temporally regulated Caulobacter promoter by upstream and downstream sequence elements
Author(s) -
Marques Marills V.,
Gober James W.
Publication year - 1995
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1995.tb02300.x
Subject(s) - caulobacter crescentus , biology , enhancer , transcription (linguistics) , promoter , operon , upstream activating sequence , gene , response element , transcription factor , cell cycle , trans acting , microbiology and biotechnology , gene expression , genetics , mutant , linguistics , philosophy
Summary The flagellar genes of Caulobacter crescentus are expressed under cell‐cycle control. Expression is regulated by both flagellar assembly cues and cell‐cycle events. In this paper we define the sequences required for the expression of the fIgF operon, a new class of σ 54 flagellar promoter. This promoter type is expressed in the middle portion of the cell cycle and regulates the expression of basal‐body genes. DNase I footprinting and mutagenesis demonstrates that an integration host factor (IHF)‐binding site is required for maximal levels of transcription of the fIgF promoter. In addition to containing a conventional upstream enhancer element (RE‐1), this promoter is unusual in that it also requires sequences (element RE‐2) immediately downstream of the transcriptional start site for maximal levels of gene expression. Cell‐cycle experiments indicate that RE‐1 and RE‐2 contribute equally to the regulation of temporal transcription. The presence of two intact elements in the promoter results in a fourfold increase in promoter activity compared with a promoter containing only one intact element, suggesting that these two elements may function synergistically to activate transcription.