Cell division is required for resolution of dimer chromosomes at the dif locus of Escherichia coli.
The dif locus is a RecA-independent resolvase site in the terminus region of the chromosome of Escherichia coli. The locus reduces dimer chromosomes, which result from sister chromatid exchange, to monomers. A density label assay demonstrates that recombination occurs at dif, and that it requires XerC and XerD. The frequency of this recombination is approximately 14% per site per generation, which is doubled in polA12 mutants. We have determined that recombination occurs late in the cell cycle, and that resolution is blocked if cell division is inhibited with cephalexin or by a ftsZts mutation. Fluorescence microscopy has demonstrated that abnormal nucleoids are present in cells incubated in cephalexin, and this is increased in polA12 mutants.
Steiner
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WW
Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder 80309, USA. steiner@ucsu.colorado.edu
Kuempel
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PL
D001665:Binding Sites; D002455:Cell Division; D002876:Chromosomes, Bacterial / Q000737:chemistry / Q000502:physiology; D004254:DNA Nucleotidyltransferases / Q000235:genetics; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics*; D029968:Escherichia coli Proteins; D019426:Integrases; D016296:Mutagenesis; D045522:Recombinases; D011995:Recombination, Genetic; D012854:Sister Chromatid Exchange
D029968:Escherichia coli Proteins; D045522:Recombinases; C473360:XerC protein, E coli; D004254:DNA Nucleotidyltransferases; D019426:Integrases; C473361:XerD protein, E coli; C115006:integron integrase IntI1