title: P1 Ref Endonuclease: A Molecular Mechanism for Phage-Enhanced Antibiotic Lethality.
abstract: Ref is an HNH superfamily endonuclease that only cleaves DNA to which RecA protein is bound. The enigmatic physiological function of this unusual enzyme is defined here. Lysogenization by bacteriophage P1 renders E. coli more sensitive to the DNA-damaging antibiotic ciprofloxacin, an example of a phenomenon termed phage-antibiotic synergy (PAS). The complementary effect of phage P1 is uniquely traced to the P1-encoded gene ref. Ref is a P1 function that amplifies the lytic cycle under conditions when the bacterial SOS response is induced due to DNA damage. The effect of Ref is multifaceted. DNA binding by Ref interferes with normal DNA metabolism, and the nuclease activity of Ref enhances genome degradation. Ref also inhibits cell division independently of the SOS response. Ref gene expression is toxic to E. coli in the absence of other P1 functions, both alone and in combination with antibiotics. The RecA proteins of human pathogens Neisseria gonorrhoeae and Staphylococcus aureus serve as cofactors for Ref-mediated DNA cleavage. Ref is especially toxic during the bacterial SOS response and the limited growth of stationary phase cultures, targeting aspects of bacterial physiology that are closely associated with the development of bacterial pathogen persistence.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Erin A
authors.initials: EA
authors.lastname: Ronayne
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Y C Serena
authors.initials: YC
authors.lastname: Wan
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Beth A
authors.initials: BA
authors.lastname: Boudreau
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.|Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Robert
authors.initials: R
authors.lastname: Landick
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Cox
mesh_terms: D017101:Bacteriophage P1 / Q000235:genetics; D002939:Ciprofloxacin / Q000494:pharmacology*; D004249:DNA Damage / Q000187:drug effects / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004720:Endonucleases / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D006801:Humans; D008242:Lysogeny / Q000235:genetics; D009344:Neisseria gonorrhoeae / Q000187:drug effects; D011938:Rec A Recombinases / Q000235:genetics*; D013014:SOS Response, Genetics; D013211:Staphylococcus aureus / Q000187:drug effects; D014764:Viral Proteins / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; D014764:Viral Proteins; D002939:Ciprofloxacin; D011938:Rec A Recombinases; D004720:Endonucleases