title: RecA-dependent mutants in Escherichia coli reveal strategies to avoid chromosomal fragmentation.
abstract: RecA- and RecBC-catalyzed repair in eubacteria assembles chromosomes fragmented by double-strand breaks. We propose that recA mutants, being unable to repair fragmented chromosomes, depend on various strategies designed to avoid chromosomal fragmentation. To identify chromosomal fragmentation-avoidance strategies, we screened for Escherichia coli mutants synthetically inhibited in combination with recA inactivation by identifying clones unable to lose a plasmid carrying the recA(+) gene. Using this screen, we have isolated several RecA-dependent mutants and assigned them to three distinct areas of metabolism. The tdk and rdgB mutants affect synthesis of DNA precursors. The fur, ubiE, and ubiH mutants are likely to have increased levels of reactive oxygen species. The seqA, topA mutants and an insertion in smtA perturbing the downstream mukFEB genes affect nucleoid administration. All isolated mutants show varying degree of SOS induction, indicating elevated levels of chromosomal lesions. As predicted, mutants in rdgB, seqA, smtA, topA, and fur show increased levels of chromosomal fragmentation in recBC mutant conditions. Future characterization of these RecA-dependent mutants will define mechanisms of chromosomal fragmentation avoidance.
authors.affiliation: Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801-3709, USA. kuzminov@life.uiuc.edu
authors.forename: Elena A
authors.initials: EA
authors.lastname: Kouzminova
authors.forename: Ella
authors.initials: E
authors.lastname: Rotman
authors.forename: Lee
authors.initials: L
authors.lastname: Macomber
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Andrei
authors.initials: A
authors.lastname: Kuzminov
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D002876:Chromosomes, Bacterial / Q000235:genetics; D053938:DNA Fragmentation; D004265:DNA Helicases / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics; D005798:Genes, Bacterial; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D013014:SOS Response, Genetics
chemical_list: D001425:Bacterial Outer Membrane Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C089746:SeqA protein, E coli; D000251:Adenosine Triphosphatases; D004265:DNA Helicases