A dedicated translation factor controls the synthesis of the global regulator Fis

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Description/Abstract

BipA is a highly conserved protein with global regulatory
properties in Escherichia coli. We show here that it functions
as a translation factor that is required specifically for
the expression of the transcriptional modulator Fis. BipA
binds to ribosomes at a site that coincides with that of
elongation factor G and has a GTPase activity that is
sensitive to high GDP:GTP ratios and stimulated by 70S
ribosomes programmed with mRNA and aminoacylated
tRNAs. The growth rate-dependent induction of BipA
allows the efficient expression of Fis, thereby modulating
a range of downstream processes, including DNA metabolism
and type III secretion. We propose a model in which
BipA destabilizes unusually strong interactions between
the 50 untranslated region of fis mRNA and the ribosome.
Since BipA spans phylogenetic domains, transcript-selective
translational control for the ‘fast-track’ expression of
specific mRNAs may have wider significance.