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Journal of Bacteriology, December 1999, p. 7558-7565, Vol. 181, No. 24
Department of Chemistry and Biochemistry and
Molecular Biology Institute, University of California, Los Angeles,
California 90095
Received 29 July 1999/Accepted 29 September 1999
The tetranucleotide core recognition sequence (TTGC) of the sigma
54 promoter
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Regulation of Sigma 54-Dependent Transcription by
Core Promoter Sequences: Role of
12 Region Nucleotides
12 recognition element was altered by random substitution. The resulting promoter mutants were characterized in vivo
and in vitro. Deregulated promoters were identified, implying that this
core element can mediate the response to enhancer-binding proteins.
These promoters had in common a substitution at position
12
(consensus C), indicating its importance for keeping basal transcription in check. In another screen, nonfunctional promoters were
identified. Their analysis indicated that positions
13 (consensus G)
and
15 (consensus T) are important to maintain minimal promoter function. In vitro studies showed that the
13 and
15 positions contribute to closed-complex formation, whereas the
12 position has a
stronger effect on recognition of the fork junction intermediate created during open-complex formation. Overall the data indicate that
the
12 region core contains specific subsequences that direct the
diverse RNA polymerase interactions required both to produce RNA and to
restrict this RNA synthesis in the absence of activation.
*
Corresponding author. Mailing address: Department of
Chemistry and Biochemistry and Molecular Biology Institute, University of California, Los Angeles, CA 90095. Phone: (310) 825-1620. Fax: (310) 267-2302. E-mail: gralla{at}mbi.ucla.edu.
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