Premium
The bacteriophage T4 AsiA protein: a molecular switch for sigma 70‐dependent promoters
Author(s) -
Colland Frédéric,
Orsini Gilbert,
Brody Edward N.,
Buc Henri,
Kolb Annie
Publication year - 1998
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 - 10.1046/j.1365-2958.1998.00729.x
Subject(s) - promoter , biology , sigma factor , rna polymerase , transcription (linguistics) , bacteriophage , transcription factor , microbiology and biotechnology , genetics , gene , escherichia coli , gene expression , linguistics , philosophy
The AsiA protein, encoded by bacteriophage T4, inhibits Eσ 70 ‐dependent transcription at bacterial and early‐phage promoters. We demonstrate that the inhibitory action of AsiA involves interference with the recognition of the −35 consensus promoter sequence by host RNA polymerase. In vitro experiments were performed with a C‐terminally labelled sigma factor that is competent for functional holoenzyme reconstitution. By protease and hydroxyl radical protein footprinting, we show that AsiA binds region 4.2 of σ 70 , which recognizes the −35 sequence. Direct interference with the recognition of the promoter at this locus is supported by two parallel experiments. The stationary‐phase sigma factor containing holoenzyme, which can initiate transcription at promoters devoid of a −35 region, is insensitive to AsiA inhibition. The recognition of a galP1 promoter by Eσ 70 is not affected by the presence of AsiA. Therefore, we conclude that AsiA inhibits transcription from Escherichia coli and T4 early promoters by counteracting the recognition of region 4.2 of σ 70 with the −35 hexamer.