title: Ciprofloxacin is an inhibitor of the Mcm2-7 replicative helicase.
abstract: Most currently available small molecule inhibitors of DNA replication lack enzymatic specificity, resulting in deleterious side effects during use in cancer chemotherapy and limited experimental usefulness as mechanistic tools to study DNA replication. Towards development of targeted replication inhibitors, we have focused on Mcm2-7 (minichromosome maintenance protein 2-7), a highly conserved helicase and key regulatory component of eukaryotic DNA replication. Unexpectedly we found that the fluoroquinolone antibiotic ciprofloxacin preferentially inhibits Mcm2-7. Ciprofloxacin blocks the DNA helicase activity of Mcm2-7 at concentrations that have little effect on other tested helicases and prevents the proliferation of both yeast and human cells at concentrations similar to those that inhibit DNA unwinding. Moreover, a previously characterized mcm mutant (mcm4chaos3) exhibits increased ciprofloxacin resistance. To identify more potent Mcm2-7 inhibitors, we screened molecules that are structurally related to ciprofloxacin and identified several that compromise the Mcm2-7 helicase activity at lower concentrations. Our results indicate that ciprofloxacin targets Mcm2-7 in vitro, and support the feasibility of developing specific quinolone-based inhibitors of Mcm2-7 for therapeutic and experimental applications.
authors.affiliation: *Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, U.S.A.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Simon
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Bochman
authors.affiliation: *Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, U.S.A.
authors.forename: Sandlin
authors.initials: S
authors.lastname: Seguin
authors.affiliation: *Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, U.S.A.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Brodsky
authors.affiliation: †Drug Discovery Center, University of Cincinnati, Cincinnati, OH 45237, U.S.A.
authors.forename: William L
authors.initials: WL
authors.lastname: Seibel
authors.affiliation: *Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, U.S.A.
authors.forename: Anthony
authors.initials: A
authors.lastname: Schwacha
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D002460:Cell Line; D002939:Ciprofloxacin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D020128:Inhibitory Concentration 50; D064110:Minichromosome Maintenance Proteins / Q000037:antagonists & inhibitors*; D015242:Ofloxacin / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000037:antagonists & inhibitors*
chemical_list: D000903:Antibiotics, Antineoplastic; D029701:Saccharomyces cerevisiae Proteins; D002939:Ciprofloxacin; D015242:Ofloxacin; D064110:Minichromosome Maintenance Proteins