RRC ID 29804
著者 Dorman CJ, Lynch AS, Ni Bhriain N, Higgins CF.
タイトル DNA supercoiling in Escherichia coli: topA mutations can be suppressed by DNA amplifications involving the tolC locus.
ジャーナル Mol Microbiol
Abstract The level of DNA supercoiling is crucial for many cellular processes, including gene expression, and is determined, primarily, by the opposing actions of two enzymes: topoisomerase I and DNA gyrase. Escherichia coli strains lacking topoisomerase I (topA mutants) normally fail to grow in the absence of compensatory mutations which are presumed to relax DNA. We have found that, in media of low osmolarity, topA mutants are viable in the absence of any compensatory mutation, consistent with the view that decreased extracellular osmolarity causes a relaxation of cellular DNA. At higher osmolarity most compensatory mutations, as expected, are in the gyrA and gyrB genes. The only other locus at which compensatory mutations arise, designated toc, is shown to involve the amplification of a region of chromosomal DNA which includes the tolC gene. However, amplification of tolC alone is insufficient to explain the phenotypes of toc mutants. tolC insertion mutations alter the distribution of plasmid topoisomers in vivo. This effect is probably indirect, possibly a result of altered membrane structure and an alteration in the cell's osmotic barrier. As tolC is a highly pleiotropic locus, affecting the expression of many genes, it is possible that some of the TolC phenotypes are a direct result of this topological change. The possible relationship between toc and tolC mutations, and the means by which tolC mutations might affect DNA supercoiling, are discussed.
巻・号 3(4)
ページ 531-40
公開日 1989-4-1
DOI 10.1111/j.1365-2958.1989.tb00199.x
PMID 2548062
MeSH Blotting, Southern DNA Topoisomerases, Type I / genetics* DNA Topoisomerases, Type I / physiology* DNA Topoisomerases, Type II / genetics DNA Topoisomerases, Type II / physiology DNA, Bacterial / genetics DNA, Superhelical / genetics* DNA, Superhelical / physiology Escherichia coli / enzymology Escherichia coli / genetics* Gene Amplification* Gene Rearrangement Genes, Bacterial* Genes, Regulator* Osmolar Concentration Oxygen / pharmacology Phenotype Plasmids Species Specificity Suppression, Genetic*
IF 3.418
引用数 49
WOS 分野 MICROBIOLOGY BIOCHEMISTRY & MOLECULAR BIOLOGY
リソース情報
原核生物(大腸菌) ME8780