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Journal of Bacteriology, April 1999, p. 2017-2025, Vol. 181, No. 7
Laboratory for Molecular Biology, Department
of Biological Sciences, University of Illinois at Chicago, Chicago,
Illinois 60607
Received 27 August 1998/Accepted 14 January 1999
The PhoP-PhoR two-component regulatory system controls the
phosphate deficiency response in B. subtilis. A number of
Pho regulon genes which require PhoP~P for activation or repression
have been identified. The studies reported here were initiated to
understand the PhoP-DNA interaction necessary for Pho promoter
regulation. The regulatory region of phoD was characterized
in detail using oligo-directed mutagenesis, DNase I footprinting, and
in vivo transcription assays. These data reveal basic principles of
PhoP binding relevant to PhoP's interaction with other Pho regulon promoters. Our results show that: (i) a dimer of PhoP~P is able to
bind two consensus repeats in a stable fashion; (ii) PhoP binding is
highly cooperative within the core promoter region, which is located
from
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Mutational Analysis of the phoD Promoter
in Bacillus subtilis: Implications for PhoP Binding and
Promoter Activation of Pho Regulon Promoters
and
66 to
17 on the coding strand and contains four TT(A/T/C)ACA-like repeats; (iii) specific bases comprising the TT(A/T/C)ACA consensus are essential for transcriptional activation, but the specific base pairs of the intervening sequences separating the
consensus repeats are not important for either PhoP binding or promoter
activation; (iv) the spacing between two consensus repeats within a
putative dimer binding site in the core region is important for both
PhoP binding and promoter activation; (v) the exact spacing between two
dimer binding sites within the core region is important for promoter
activation but less so for PhoP binding affinity, as long as the
repeats are on the same face of the helix; and (vi) the 5' secondary
binding region is important for coordinated PhoP binding to the core
binding region, making it nearly essential for promoter activation.
*
Corresponding author. Mailing address: Laboratory for
Molecular Biology (M/C 567), 900 S. Ashland Ave., University of
Illinois at Chicago, Chicago, IL 60607. Phone: (312) 996-5460. Fax:
(312) 413-2691. E-mail: Hulett{at}uic.edu.
Present address: Department of Molecular Pharmacology, Stanford
University School of Medicine, Stanford, CA 94305.
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