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Molecular Mechanisms of Transcription Initiation at gal Promoters and their Multi-Level Regulation by GalR, CRP and DNA Loop

Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA
Author to whom correspondence should be addressed.
Academic Editors: Sivaramesh Wigneshweraraj and Deborah M. Hinton
Biomolecules 2015, 5(4), 2782-2807;
Received: 11 May 2015 / Accepted: 25 September 2015 / Published: 16 October 2015
(This article belongs to the Special Issue Bacterial RNA Polymerase)
PDF [12931 KB, uploaded 16 October 2015]


Studying the regulation of transcription of the gal operon that encodes the amphibolic pathway of d-galactose metabolism in Escherichia coli discerned a plethora of principles that operate in prokaryotic gene regulatory processes. In this chapter, we have reviewed some of the more recent findings in gal that continues to reveal unexpected but important mechanistic details. Since the operon is transcribed from two overlapping promoters, P1 and P2, regulated by common regulatory factors, each genetic or biochemical experiment allowed simultaneous discernment of two promoters. Recent studies range from genetic, biochemical through biophysical experiments providing explanations at physiological, mechanistic and single molecule levels. The salient observations highlighted here are: the axiom of determining transcription start points, discovery of a new promoter element different from the known ones that influences promoter strength, occurrence of an intrinsic DNA sequence element that overrides the transcription elongation pause created by a DNA-bound protein roadblock, first observation of a DNA loop and determination its trajectory, and piggybacking proteins and delivering to their DNA target. View Full-Text
Keywords: activation; repression; DNA looping; transcription; galactose operon activation; repression; DNA looping; transcription; galactose operon

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Lewis, D.E.; Adhya, S. Molecular Mechanisms of Transcription Initiation at gal Promoters and their Multi-Level Regulation by GalR, CRP and DNA Loop. Biomolecules 2015, 5, 2782-2807.

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