The world's first wiki where authorship really matters (Nature Genetics, 2008). Due credit and reputation for authors. Imagine a global collaborative knowledge base for original thoughts. Search thousands of articles and collaborate with scientists around the globe.

wikigene or wiki gene protein drug chemical gene disease author authorship tracking collaborative publishing evolutionary knowledge reputation system wiki2.0 global collaboration genes proteins drugs chemicals diseases compound
Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 

Editor

Share

Personal info

View

Links

Table of contents

About

Terms

 

Gene Review: 

topA  -  DNA topoisomerase I

Salmonella enterica subsp. enterica serovar Typhimurium str. LT2

 
 
Welcome! If you are familiar with the subject of this article, you can contribute to this open access knowledge base by deleting incorrect information, restructuring or completely rewriting any text. Read more.
 

Disease relevance of topA

  • The leu-500 promoter is inactivated by a mutation in the -10 region but can be activated in topA Escherichia coli and Salmonella strains [1].
  • The leu-500 promoter of Salmonella typhimurium is a mutant and inactive variant of the leucine operon promoter that regains activity if negative DNA supercoiling rises above normal levels, typically as a result of mutations affecting DNA topoisomerase I (topA mutants) [2].
 

High impact information on topA

  • Furthermore, when cloned onto a multicopy plasmid, the leu-500 promoter failed to function, even in a topA background [3].
  • Activation of the leu-500 promoter was analysed in topA mutant cells harbouring transcriptionally inducible tet or cat gene cassettes inserted in the region upstream from the leu operon [2].
  • Mutations affecting DNA topoisomerase I (topA) in Salmonella typhimurium were isolated and graded on the basis of their ability to reverse the effects of gyrB mutations on his operon expression [4].
  • Nevertheless, invA was poorly expressed in topA mutants of S. typhimurium, which have increased DNA superhelicity [5].
  • This position-dependent supercoiling effect on gene activation is best illustrated in the study of the suppression of the leu-500 mutation of the leuABCD operon in a Salmonella typhimurium topA mutant [6].
 

Biological context of topA

  • Expression of the lacZ gene from the supercoiling-sensitive leu-500 promoter on a plasmid in topA mutant cells was stimulated by activating a divergently oriented Tac promoter, 400 bp upstream from leu-500 [7].
  • Using the suppression of the leu-500 mutation in Salmonella typhimurium topA mutants as a model system, we put forward our view of the effects of transcription-driven DNA supercoiling on gene expression control [8].
 

Associations of topA with chemical compounds

  • S. typhimurium strains carrying either point or deletion mutations in topA had previously been shown to lose their mutability by UV or methyl methanesulfonate (K. Overbye and P. Margolin, J. Bacteriol. 146:170-178, 1981; K. Overbye, S. M. Basu, and P. Margolin, Cold Spring Harbor Symp. Quant. Biol. 47:785-791, 1983) [9].

References

  1. Activation of the leu-500 promoter by a reversed polarity tetA gene. Response to global plasmid supercoiling. Chen, D., Bachellier, S., Lilley, D.M. J. Biol. Chem. (1998) [Pubmed]
  2. Activation and silencing of leu-500 promoter by transcription-induced DNA supercoiling in the Salmonella chromosome. El Hanafi, D., Bossi, L. Mol. Microbiol. (2000) [Pubmed]
  3. DNA supercoiling and the leu-500 promoter mutation of Salmonella typhimurium. Richardson, S.M., Higgins, C.F., Lilley, D.M. EMBO J. (1988) [Pubmed]
  4. The relative contributions of transcription and translation to plasmid DNA supercoiling in Salmonella typhimurium. Spirito, F., Figueroa-Bossi, N., Bossi, L. Mol. Microbiol. (1994) [Pubmed]
  5. Expression of Salmonella typhimurium genes required for invasion is regulated by changes in DNA supercoiling. Galán, J.E., Curtiss, R. Infect. Immun. (1990) [Pubmed]
  6. A promoter relay mechanism for sequential gene activation. Fang, M., Wu, H.Y. J. Bacteriol. (1998) [Pubmed]
  7. Long-distance effect of downstream transcription on activity of the supercoiling-sensitive leu-500 promoter in a topA mutant of Salmonella typhimurium. Spirito, F., Bossi, L. J. Bacteriol. (1996) [Pubmed]
  8. Transcription-driven DNA supercoiling and gene expression control. Chen, C.C., Wu, H.Y. Front. Biosci. (2003) [Pubmed]
  9. An inducible pathway is required for mutagenesis in Salmonella typhimurium LT2. Orrego, C., Eisenstadt, E. J. Bacteriol. (1987) [Pubmed]
Contributions to this collaborative article are from individual authors of WikiGenes or mined by the WikiGenes Data Mining Engine from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.About WikiGenesOpen Access LicencePrivacy PolicyTerms of Useapsburg
 
WikiGenes - Universities