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J Mol Biol. 1988 Aug 20;202(4):735-42.

Multiple promoters for transcription of the Escherichia coli DNA topoisomerase I gene and their regulation by DNA supercoiling.

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  • 1E. I. du Pont de Nemours and Co. Central Research and Development Department, Wilmington, DE 19898.

Abstract

There are four transcriptional promoters present in the 5' control region of the Escherichia coli DNA topoisomerase I (topA) gene. These were identified with Bal31 nuclease-generated deletions and mapping of the 5' ends of the mRNAs with avian reverse transcriptase. Recombinant plasmids with all or some of these promoters fused to the galactokinase (galK) gene-coding region have been constructed and used to study transcription from the promoters both in vitro and in vivo. The promoter (P1) closest to the starting ATG codon has a near consensus -35 sequence (GTTGATA) but unusual -10 (CATATCG) sequence. The other three promoters (P2, P3 and P4) are clustered together 60 base-pairs further upstream. Negative DNA supercoiling is required for efficient transcription from P1, P1 + P2 + P3 + P4, P2 + P3 + P4, P3 + P4 and P4 alone. The combination of all four promoters demonstrates greater supercoiling dependence than does any of the other subsets tested.

PMID:
2845101
[PubMed - indexed for MEDLINE]
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