title: DNA Metabolism in Balance: Rapid Loss of a RecA-Based Hyperrec Phenotype.
abstract: The RecA recombinase of Escherichia coli has not evolved to optimally promote DNA pairing and strand exchange, the key processes of recombinational DNA repair. Instead, the recombinase function of RecA protein represents an evolutionary compromise between necessary levels of recombinational DNA repair and the potentially deleterious consequences of RecA functionality. A RecA variant, RecA D112R, promotes conjugational recombination at substantially enhanced levels. However, expression of the D112R RecA protein in E. coli results in a reduction in cell growth rates. This report documents the consequences of the substantial selective pressure associated with the RecA-mediated hyperrec phenotype. With continuous growth, the deleterious effects of RecA D112R, along with the observed enhancements in conjugational recombination, are lost over the course of 70 cell generations. The suppression reflects a decline in RecA D112R expression, associated primarily with a deletion in the gene promoter or chromosomal mutations that decrease plasmid copy number. The deleterious effects of RecA D112R on cell growth can also be negated by over-expression of the RecX protein from Neisseria gonorrhoeae. The effects of the RecX proteins in vivo parallel the effects of the same proteins on RecA D112R filaments in vitro. The results indicate that the toxicity of RecA D112R is due to its persistent binding to duplex genomic DNA, creating barriers for other processes in DNA metabolism. A substantial selective pressure is generated to suppress the resulting barrier to growth.
authors.affiliation: Petersburg Nuclear Physics Institute, NRC Kurchatov Institute, Gatchina, 188300, Russia.|Peter the Great St. Petersburg Polytechnic University, Saint-Petersburg, 195251, Russia.
authors.forename: Irina V
authors.initials: IV
authors.lastname: Bakhlanova
authors.affiliation: Petersburg Nuclear Physics Institute, NRC Kurchatov Institute, Gatchina, 188300, Russia.
authors.forename: Alexandra V
authors.initials: AV
authors.lastname: Dudkina
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706-1544, United States of America.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Wood
authors.affiliation: Petersburg Nuclear Physics Institute, NRC Kurchatov Institute, Gatchina, 188300, Russia.
authors.forename: Vladislav A
authors.initials: VA
authors.lastname: Lanzov
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706-1544, United States of America.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Cox
authors.affiliation: Petersburg Nuclear Physics Institute, NRC Kurchatov Institute, Gatchina, 188300, Russia.|Peter the Great St. Petersburg Polytechnic University, Saint-Petersburg, 195251, Russia.
authors.forename: Dmitry M
authors.initials: DM
authors.lastname: Baitin
mesh_terms: D019943:Amino Acid Substitution; D001120:Arginine / Q000378:metabolism; D001224:Aspartic Acid / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D005838:Genotype; D009154:Mutation; D009344:Neisseria gonorrhoeae / Q000737:chemistry; D010641:Phenotype; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011938:Rec A Recombinases / Q000235:genetics* / Q000378:metabolism; D059767:Recombinational DNA Repair
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C430523:RecX protein, Xanthomonas campestris; D001224:Aspartic Acid; D001120:Arginine; D011938:Rec A Recombinases