title: Identification and characterization of human Rad51 inhibitors by screening of an existing drug library.
abstract: Homologous Recombination (HR) plays an essential role in cellular proliferation and in maintaining genomic stability by repairing DNA double-stranded breaks that appear during replication. Rad51, a key protein of HR in eukaryotes, can have an elevated expression level in tumor cells, which correlates with their resistance to anticancer therapies. Therefore, targeted inhibition of Rad51 through inhibitor may improve the tumor response to these therapies. In order to identify small molecules that inhibit Rad51 activity, we screened the Prestwick Library (1120 molecules) for their effect on the strand exchange reaction catalyzed by Rad51. We found that Chicago Sky Blue (CSB) is a potent inhibitor of Rad51, showing IC₅₀ values in the low nanomolar range (400 nM). Biochemical analysis demonstrated that the inhibitory mechanism probably occurs by disrupting the Rad51 association with the single-stranded DNA, which prevents the nucleoprotein filament formation, the first step of the protein activity. Structure Activity Relationship analysis with a number of compounds that shared structure homology with CSB was also performed. The sensitivity of Rad51 inhibition to CSB modifications suggests specific interactions between the molecule and Rad51 nucleofilament. CSB and some of its analogs open up new perspectives in the search for agents capable of potentiating chemo- and radio-therapy treatments for cancer. Moreover, these compounds may be excellent tools to analyze Rad51 cellular functions. Our study also highlights how CSB and its analogs, which are frequently used in colorants, stains and markers, could be responsible of unwanted side effects by perturbing the DNA repair process.
authors.affiliation: Research Unit UFIP UMR 6286, Centre National de la Recherche Scientifique & University of Nantes, F-44322 Nantes cedex 3, France.
authors.forename: Anaïs
authors.initials: A
authors.lastname: Normand
authors.affiliation: Research Unit UFIP UMR 6286, Centre National de la Recherche Scientifique & University of Nantes, F-44322 Nantes cedex 3, France.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Rivière
authors.affiliation: Research Unit UFIP UMR 6286, Centre National de la Recherche Scientifique & University of Nantes, F-44322 Nantes cedex 3, France. Electronic address: axelle.renodon-corniere@univ-nantes.fr.
authors.forename: Axelle
authors.initials: A
authors.lastname: Renodon-Cornière
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D004260:DNA Repair / Q000187:drug effects; D004277:DNA, Single-Stranded / Q000378:metabolism; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004586:Electrophoresis / Q000379:methods; D015180:Electrophoresis, Gel, Two-Dimensional; D059765:Homologous Recombination / Q000187:drug effects; D006801:Humans; D020128:Inhibitory Concentration 50; D051135:Rad51 Recombinase / Q000037:antagonists & inhibitors*; D054852:Small Molecule Libraries / Q000737:chemistry / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D014343:Trypan Blue / Q000494:pharmacology
chemical_list: D004277:DNA, Single-Stranded; D054852:Small Molecule Libraries; C009000:pontamine sky blue; D000255:Adenosine Triphosphate; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; D014343:Trypan Blue
keywords: Anticancer agent; Homologous recombination; Inhibitor; Multidrug resistance; Rad51