title: Type I topoisomerase activity is required for proper chromosomal segregation in Escherichia coli.
abstract: Type I DNA topoisomerases are ubiquitous enzymes involved in many aspects of DNA metabolism. Escherichia coli possesses two type I topoisomerase activities, DNA topoisomerase I (Topo I) and III (Topo III). The gene encoding Topo III (topB) can be deleted without affecting cell viability. Cells possessing a deletion of the gene encoding Topo I (topA) are only viable in the presence of an additional compensatory mutation. In the presence of compensatory mutations, Topo I deletion strains grow normally; however, if Topo III activity is repressed in these cells, they filament extensively and possess an abnormal nucleoid structure. These defects can be suppressed by the deletion of the recA gene, suggesting that these enzymes may be involved in RecA-mediated recombination and may specifically resolve recombination intermediates before partitioning.
authors.affiliation: Molecular and Cell Biology Program, University of Maryland, Baltimore 21201, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Zhu
authors.forename: P
authors.initials: P
authors.lastname: Pongpech
authors.forename: R J
authors.initials: RJ
authors.lastname: DiGate
mesh_terms: D000705:Anaphase; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002876:Chromosomes, Bacterial / Q000502:physiology*; D004264:DNA Topoisomerases, Type I / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins; D017353:Gene Deletion; D008856:Microscopy, Fluorescence; D010641:Phenotype; D011938:Rec A Recombinases / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000502:physiology; D011995:Recombination, Genetic / Q000235:genetics; D012697:Serine Endopeptidases / Q000235:genetics; D013489:Suppression, Genetic; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D004264:DNA Topoisomerases, Type I; D029968:Escherichia coli Proteins; D011938:Rec A Recombinases; D011993:Recombinant Fusion Proteins; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein; C053139:sulA protein, E coli