Affiliation:
1. Department of Microbiology, University of Washington, Seattle, Washington 98195
Abstract
ABSTRACT
Salmonella enterica
has two antigenically distinct flagellin genes,
fliC
and
fljB
, that are alternatively expressed. The
fljA
gene is cotranscribed with
fljB
and encodes a protein that has been characterized as a transcriptional repressor of the unlinked
fliC
gene when FljB is expressed. In this study we report genetic evidence that FljA prevents the production of FliC protein through an interaction with the 5′-untranslated region of the
fliC
mRNA transcript. Studies with operon and gene fusions, Western analyses, and T
2
RNase protection assays were performed for strains with the
fljBA
promoter locked in either the on or the off orientation. β-Galactosidase assays of
fliC
transcriptional and translational fusions to the
lac
operon demonstrated that while FljA inhibits
fliC
transcription fivefold in the
fljBA
ON
orientation, it has a 200-fold effect on both
fliC
transcription and translation, indicating that the FljA inhibitor might act at both the transcriptional and translational level. T
2
RNase protection assays also demonstrated a fivefold decrease in
fliC
transcript levels for cells locked in the
fljBA
ON
orientation compared to those in the
fljBA
OFF
orientation, and an eightfold decrease in FliC protein levels was observed by Western analysis. This reduction in FliC protein levels is greater than the decrease observed for the transcript. These results are consistent with a new model whereby FljA inhibits FliC expression by an attenuation or translational control mechanism.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
136 articles.
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