Hypernegative supercoiling of the DNA template during transcription elongation in vitro

Marc Drolet, Xin Bi, Leroy-Fong Liu

Research output: Contribution to journalArticle

95 Citations (Scopus)

Abstract

Supercoiled plasmid DNAs with negative superhelicity several times higher than normal have been isolated from Escherichia coli topA mutants. The formation of these hypernegatively supercoiled plasmid DNAs is apparently induced by transcription. We show that hypernegatively supercoiled plasmid DNAs isolated from topA mutants contain R-loop(s). To study the mechanism of formation of hypernegatively supercoiled plasmid DNA, we have been able to reproduce hypernegatively supercoiled DNA in vitro using purified DNA polymerase and DNA gyrase. The formation of hypernegatively supercoiled plasmid DNA template in vitro is shown to require transcription elongation and is tightly linked to R-loop formation. We propose that one of the roles of topoisomerase I is to suppress R-loop formation during transcription elongation.

Original languageEnglish
Pages (from-to)2068-2074
Number of pages7
JournalJournal of Biological Chemistry
Volume269
Issue number3
Publication statusPublished - Jan 21 1994
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry

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