Atomic force microscopic demonstration of DNA looping by GalR and HU

Yuri L. Lyubchenko, Luda S. Shlyakhtenko, Tsunehiro Aki, Sankar Adhya

Research output: Contribution to journalArticlepeer-review

75 Scopus citations


Regulation of gene transcription in both prokaryotes and eukaryotes involves formation of various DNA-multiprotein complexes of higher order structure through communication between distant regions of DNA. The communication between distant DNA sites occurs by interaction between proteins bound to the sites by looping out the intervening DNA segments. The repression of transcription of two overlapping promoters of the gal operon in Escherichia coil requires Gal repressor (GalR) and the histone-like protein HU. Both in vivo and in vitro data support a proposed HU containing complex responsive to induction in which GalR molecules bound to two distant operator sites interact by looping out DNA. We successfully applied atomic force microscope (AFM) imaging to visualize gal DNA complexes with proteins. We report GalR mediated DNA looping in which HU plays an obligatory role by helping GalR tetramerization. Supercoiling of DNA, which is also critical for GalR action, may stabilize the DNA loops by providing an energetically favorable geometry of the DNA.

Original languageEnglish (US)
Pages (from-to)873-876
Number of pages4
JournalNucleic acids research
Issue number4
StatePublished - 1997

ASJC Scopus subject areas

  • Genetics

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