title: The Werner syndrome helicase/exonuclease (WRN) disrupts and degrades D-loops in vitro.
abstract: The loss of function of WRN, a DNA helicase and exonuclease, causes the premature aging disease Werner syndrome. A hallmark feature of cells lacking WRN is genomic instability typified by elevated illegitimate recombination events and accelerated loss of telomeric sequences. In this study, the activities of WRN were examined on a displacement loop (D-loop) DNA substrate that mimics an intermediate formed during the strand invasion step of many recombinational processes. Our results indicate that this model substrate is specifically bound by WRN and efficiently disrupted by its helicase activity. In addition, the 3' end of the inserted strand of this D-loop structure is readily attacked by the 3'-->5' exonuclease function of WRN. These results indicate that D-loop structures are favored sites for WRN action. Thus, WRN may participate in DNA metabolic processes that utilize these structures, such as recombination and telomere maintenance pathways.
authors.affiliation: Graduate Center for Toxicology, University of Kentucky, Lexington, Kentucky 40536, USA. dkorre2@pop.uky.edu
authors.forename: David K
authors.initials: DK
authors.lastname: Orren
authors.forename: Shaji
authors.initials: S
authors.lastname: Theodore
authors.forename: Amrita
authors.initials: A
authors.lastname: Machwe
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D018983:DNA Footprinting; D004265:DNA Helicases / Q000235:genetics* / Q000378:metabolism*; D017931:DNA Primers; D003850:Deoxyribonuclease I / Q000378:metabolism; D019281:Dimerization; D024202:Electrophoretic Mobility Shift Assay; D005090:Exodeoxyribonucleases; D005092:Exonucleases / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D053484:RecQ Helicases; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D014898:Werner Syndrome / Q000201:enzymology*; D000071657:Werner Syndrome Helicase
chemical_list: D017931:DNA Primers; D011994:Recombinant Proteins; D004247:DNA; D005090:Exodeoxyribonucleases; D005092:Exonucleases; D003850:Deoxyribonuclease I; D004265:DNA Helicases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase