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Cell. 1992 Aug 7;70(3):501-12.

Polypeptides containing highly conserved regions of transcription initiation factor sigma 70 exhibit specificity of binding to promoter DNA.

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Department of Bacteriology, University of Wisconsin, Madison 53706.


The sigma 70 subunit of E. coli RNA polymerase is required for sequence-specific recognition of promoter DNA. Genetic studies and sequence analysis have indicated that sigma 70 contains two specific DNA-binding domains that recognize the two conserved portions of the prokaryotic promoter. However, intact sigma 70 does not bind to DNA. Using C-terminal and internal polypeptides of sigma 70, carrying one or both putative DNA-binding domains, we demonstrate that sigma 70 does contain two DNA-binding domains, but that N-terminal sequences inhibit the ability of intact sigma 70 to bind to DNA. Thus, we propose that sigma 70 is a sequence-specific DNA-binding protein that normally functions through an allosteric interaction with the core subunits of RNA polymerase.

[Indexed for MEDLINE]

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