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Strong inhibition of fimbrial 3 subunit gene transcription by a novel downstream repressive element in B ordetella pertussis
Author(s) -
Chen Qing,
Boulanger Alice,
Hinton Deborah M.,
Stibitz Scott
Publication year - 2014
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/mmi.12690
Subject(s) - promoter , biology , transcription (linguistics) , response element , microbiology and biotechnology , gene , transcription factor , genetics , gene expression , linguistics , philosophy
Summary The Bvg ‐regulated promoters for the fimbrial subunit genes fim2 and fim3 of B ordetella pertussis behave differently from each other both in vivo and in vitro . In vivo P fim2 is significantly stronger than P fim3 , even though predictions based on the DNA sequences of BvgA ‐binding motifs and core promoter elements would indicate the opposite. In vitro P fim3 demonstrated robust BvgA ∼ P ‐dependent transcriptional activation, while none was seen with P fim2 . This apparent contradiction was investigated further. By swapping sequence elements we created a number of hybrid promoters and assayed their strength in vivo . We found that, while P fim3 promoter elements upstream of the +1 transcriptional start site do indeed direct Bvg ‐activated transcription more efficiently than those of P fim2 , the overall promoter strength of P fim3 in vivo is reduced due to sequences downstream of +1 that inhibit transcription more than 250‐fold. This element, the DRE ( d ownstream r epressive e lement), was mapped to the 15 bp immediately downstream of the P fim3 +1. Placing the DRE in different promoter contexts indicated that its activity was not specific to fim promoters, or even to Bvg ‐regulated promoters. However it does appear to be specific to B ordetella species in that it did not function in E scherichia coli .