Journal of Bacteriology, August 1999, p. 4704-4707, Vol. 181, No. 15
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
-Subunit
C-Terminal Domain in LuxR-Dependent Activation of the Vibrio
fischeri Luminescence Genes
Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 240611; Department of Molecular Genetics, National Institute of Genetics, Mishima, Shizuoka, 411-8540 Japan2; and Department of Microbiology, University of Iowa, Iowa City, Iowa 522423
Received 19 February 1999/Accepted 24 May 1999
LuxR is a
70 RNA polymerase (RNAP)-dependent
transcriptional activator that controls expression of the Vibrio
fischeri lux operon in response to an acylhomoserine lactone-cell
density signal. We have investigated whether the
-subunit C-terminal
domain (
CTD) of RNAP is required for LuxR activity. A purified
signal-independent, LuxR C-terminal domain-containing polypeptide
(LuxR
N) was used to study the activation of transcription from the
luxI promoter in vitro. Initiation of lux
operon transcription was observed in the presence of LuxR
N and
wild-type RNAP but not in the presence of LuxR
N and RNAPs with
truncated
CTDs. We also studied the in vivo role of the RNAP
CTD
in activation of lux transcription in Escherichia
coli. This enabled a comparison of results obtained with
full-length LuxR to those obtained with LuxR
N. These in vivo studies
indicated that both LuxR and LuxR
N require the RNAP
CTD for
activity. The results of DNase I protection studies showed that
LuxR
N-RNAP complexes can bind and protect the luxI
promoter, but with less efficacy when the
CTD is truncated in
comparison to the wild type. Thus, both in vitro and in vivo
experiments demonstrated that LuxR-dependent transcriptional activation
of the lux operon involves the RNAP
CTD and suggest that
CTD-LuxR interactions may play a role in recruitment of RNAP to the
luxI promoter.
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