DNA supercoiling changes the spacing requirement of two lac operators for DNA loop formation with lac repressor.

H. Krämer, M. Amouyal, A. Nordheim, B. Müller-Hill

Research output: Contribution to journalArticle

101 Citations (Scopus)

Abstract

We have used a gel retardation assay to investigate the influence of DNA supercoiling on loop formation between lac repressor and two lac operators. A series of 15 DNA minicircles of identical size (452 bp) was constructed carrying two lac operators at distances ranging from 153 to 168 bp. Low positive or negative supercoiling (sigma = +/- 0.023) changed the spacing between the two lac operators required for the formation of the most stable loops. This reveals the presence of altered double helical repeats (ranging from 10.3 to 10.7 bp) in supercoiled DNA minicircles. At elevated negative supercoiling (sigma = -0.046) extremely stable loops were formed at all operator distances tested, with a slight spacing periodicity remaining. After relaxation of minicircle-repressor complexes with topoisomerase I one superhelical turn was found to be constrained in those minicircles which carry operators at distances corresponding to a non-integral number of helical turns. This indicates that DNA loop formation can define local DNA domains with altered topological properties of the DNA helix.

Original languageEnglish (US)
Pages (from-to)547-556
Number of pages10
JournalEMBO Journal
Volume7
Issue number2
StatePublished - Feb 1988

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Lac Repressors
DNA
Superhelical DNA
Type I DNA Topoisomerase
Electrophoretic Mobility Shift Assay
Periodicity
Assays
Gels

ASJC Scopus subject areas

  • Cell Biology
  • Genetics

Cite this

DNA supercoiling changes the spacing requirement of two lac operators for DNA loop formation with lac repressor. / Krämer, H.; Amouyal, M.; Nordheim, A.; Müller-Hill, B.

In: EMBO Journal, Vol. 7, No. 2, 02.1988, p. 547-556.

Research output: Contribution to journalArticle

Krämer, H. ; Amouyal, M. ; Nordheim, A. ; Müller-Hill, B. / DNA supercoiling changes the spacing requirement of two lac operators for DNA loop formation with lac repressor. In: EMBO Journal. 1988 ; Vol. 7, No. 2. pp. 547-556.
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