Open AccessDNA axial rotation and the merge of oppositely supercoiled DNA domains in Escherichia coli : Effects of DNA bends
Author(s) -
Vera A. Stupina,
James C. Wang
Publication year - 2004
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0402849101
Subject(s) - dna supercoil , dna , topoisomerase , transcription (linguistics) , base pair , biology , dna clamp , merge (version control) , biophysics , microbiology and biotechnology , escherichia coli , recombinase , gene , genetics , dna replication , rna , reverse transcriptase , linguistics , philosophy , information retrieval , computer science , recombination
We have examined the issue whether axial rotation of an intracellular DNA segment several thousand base pairs in length is associated with a large friction barrier against the merge of oppositely supercoiled DNA domains. The induction of a site-specific recombinase was used to form intracellular DNA rings bearing different numbers of transcription units, and it was found that DNA rings with a single tetA gene and no other transcription units does not become excessively negatively supercoiled in Escherichia coli cells lacking DNA topoisomerase I. Thus, whereas oppositely supercoiled domains are generated in a tetA-bearing DNA ring through anchoring of the tetA transcripts to cell membrane, these domains appear to readily merge by means of axial rotation of the DNA segment connecting them. The diffusional merge of these oppositely supercoiled domains is not significantly affected by the presence of bent sequences in the intervening DNA segment. Examination of the effects of adding more transcription units to the tetA-bearing ring suggests, however, that DNA bends stabilized by bound protein molecules may significantly impede this process inside E. coli, as suggested by previous in vitro studies.