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Gyrase and Topo IV modulate chromosome domain size in vivo
Author(s) -
Staczek Pawel,
Higgins N. Patrick
Publication year - 1998
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1998.01025.x
Subject(s) - dna gyrase , dna supercoil , biology , mutant , circular bacterial chromosome , topoisomerase , dna , topoisomerase iv , chromosome , genetics , wild type , microbiology and biotechnology , chromosome segregation , dna replication , escherichia coli , gene
In bacteria, DNA supercoil movement is restricted to subchromosomal regions or ‘domains.’ To elucidate the nature of domain boundaries, we analysed reaction kinetics for γδ site‐specific resolution in six chromosomal intervals ranging in size from 14 to 90 kb. In stationary cultures of Salmonella typhimurium , resolution kinetics were rapid for both short and long intervals, suggesting that random stationary barriers occur with a 30% probability at approximately 80 kb intervals along DNA. To test the biochemical nature of domain barriers, a genetic screen was used to look for mutants with small domains. Rare temperature‐sensitive alleles of DNA gyrase and Topo IV (the two essential type II topoisomerases) had more supercoil barriers than wild‐type strains in all growth states. The most severe gyrase mutants were found to have twice as many barriers in growing cells as wild type throughout a 90 kb interval of the chromosome. We propose that knots and tangles in duplex DNA restrain supercoil diffusion in living bacteria.