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J Mol Biol. 1995 Feb 10;246(1):35-42.

A sequence-induced superhelical DNA segment serves as transcriptional enhancer.

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Department of Biology Massachusetts Institute of Technology, Cambridge 02139.


The initiation of transcription at the sigma 54-dependent promoter glnAp2 of Escherichia coli is activated by the protein NR1(NTRC)-phosphate, which binds to two sites located upstream of the promoter that together constitute an enhancer. The cooperative binding facilitates the oligomerization of NR1-phosphate endowing it with the ATPase activity required for its ability to serve as transcriptional activator. We show here that these sites can be replaced by sequence-dependent superhelical inserts, lacking any homology to the nucleotide sequence of the enhancers. These superhelical inserts, irrespective of their chirality, are as effective as the paired sites in binding NR1-phosphate and in stimulating its oligomerization. We conclude that a specific sequence of nucleotides and the three-dimensional structure of DNA can determine its affinity for the NR1 activator protein capable of binding to DNA.

[Indexed for MEDLINE]

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