Transcriptional regulation at two divergent gene promoters in Escherichia Coli K-12
Transcriptional regulation at two divergent gene promoters in Escherichia Coli K-12
The guaBA operon is located at 56 minutes on the Escherichia coli chromosome and encodes two enzymes involved in the final stages of purine biosynthesis, these are IMP dehydrogenase (guaB) and GMP synthetase (guaA).
The guaBA promoter has previously been reported to be subject to multivalent regulation via the stringent response, the DnaA protein and the purine repressor protein, PurR. The guaBA operon lies back to back with the xseA gene, which encodes the large subunit of exonuclease VII, an enzyme involved in methyl-directed mismatch repair and the degradation of single stranded DNA. The -35 promoter recognition elements of these back to back promoters lie just 20 base pairs apart, with the xseA gene transcribed in a clockwise direction, and the guaBA operon transcribed in a counter-clockwise direction, on the E.coli chromosome. The close proximity of these two genes has raised the question of interference, as each promoter competes for RNA polymerase (RNAP) binding. Studies in vitro have shown that RNAP can bind to both promoters independently but not simultaneously, which suggests that an RNAP molecule bound at one promoter will prevent a second RNAP molecule from binding to the other promoter through steric hindrance. Studies in vitro and in vivo have also shown that the promoters of both the guaBA operon and the xseA gene are subject to regulation by the cyclic AMP receptor protein (CRP) which appears to channel RNA polymerase from one promoter (xseP) to the other (guaP) during growth in the absence of glucose. The guaBA promoter is also activated by the growth phase-dependent transcriptional activator protein, Fis (factor for inversion stimulation).
The results reported here have allowed us to build up a picture of how these two genes are activated or repressed during the exponential and stationary phases of bacterial growth. There is also evidence, reported here, of a specific gua repressor to regulate the flow of purine bases into GMP.
University of Southampton
1997
Hutchings, Matthew Ian
(1997)
Transcriptional regulation at two divergent gene promoters in Escherichia Coli K-12.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The guaBA operon is located at 56 minutes on the Escherichia coli chromosome and encodes two enzymes involved in the final stages of purine biosynthesis, these are IMP dehydrogenase (guaB) and GMP synthetase (guaA).
The guaBA promoter has previously been reported to be subject to multivalent regulation via the stringent response, the DnaA protein and the purine repressor protein, PurR. The guaBA operon lies back to back with the xseA gene, which encodes the large subunit of exonuclease VII, an enzyme involved in methyl-directed mismatch repair and the degradation of single stranded DNA. The -35 promoter recognition elements of these back to back promoters lie just 20 base pairs apart, with the xseA gene transcribed in a clockwise direction, and the guaBA operon transcribed in a counter-clockwise direction, on the E.coli chromosome. The close proximity of these two genes has raised the question of interference, as each promoter competes for RNA polymerase (RNAP) binding. Studies in vitro have shown that RNAP can bind to both promoters independently but not simultaneously, which suggests that an RNAP molecule bound at one promoter will prevent a second RNAP molecule from binding to the other promoter through steric hindrance. Studies in vitro and in vivo have also shown that the promoters of both the guaBA operon and the xseA gene are subject to regulation by the cyclic AMP receptor protein (CRP) which appears to channel RNA polymerase from one promoter (xseP) to the other (guaP) during growth in the absence of glucose. The guaBA promoter is also activated by the growth phase-dependent transcriptional activator protein, Fis (factor for inversion stimulation).
The results reported here have allowed us to build up a picture of how these two genes are activated or repressed during the exponential and stationary phases of bacterial growth. There is also evidence, reported here, of a specific gua repressor to regulate the flow of purine bases into GMP.
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Published date: 1997
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Local EPrints ID: 463192
URI: http://eprints.soton.ac.uk/id/eprint/463192
PURE UUID: ed88b440-bc6c-4fd8-b462-fd5d49e2ce5a
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Date deposited: 04 Jul 2022 20:47
Last modified: 04 Jul 2022 20:47
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Author:
Matthew Ian Hutchings
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