title: Multifaceted role of the Topo IIIα-RMI1-RMI2 complex and DNA2 in the BLM-dependent pathway of DNA break end resection.
abstract: BLM, a RecQ family DNA helicase mutated in Bloom's Syndrome, participates in homologous recombination at two stages: 5' DNA end resection and double Holliday junction dissolution. BLM exists in a complex with Topo IIIα, RMI1 and RMI2. Herein, we address the role of Topo IIIα and RMI1-RMI2 in resection using a reconstituted system with purified human proteins. We show that Topo IIIα stimulates DNA unwinding by BLM in a manner that is potentiated by RMI1-RMI2, and that the processivity of resection is reliant on the Topo IIIα-RMI1-RMI2 complex. Topo IIIα localizes to the ends of double-strand breaks, thus implicating it in the recruitment of resection factors. While the single-stranded DNA binding protein RPA plays a major role in imposing the 5' to 3' polarity of resection, Topo IIIα also makes a contribution in this regard. Moreover, we show that DNA2 stimulates the helicase activity of BLM. Our results thus uncover a multifaceted role of the Topo IIIα-RMI1-RMI2 ensemble and of DNA2 in the DNA resection reaction.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Daley
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520, USA.
authors.forename: Tamara
authors.initials: T
authors.lastname: Chiba
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520, USA.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Xue
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520, USA.
authors.forename: Hengyao
authors.initials: H
authors.lastname: Niu
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06520, USA patrick.sung@yale.edu.
authors.forename: Patrick
authors.initials: P
authors.lastname: Sung
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism* / Q000502:physiology; D004247:DNA / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D004265:DNA Helicases / Q000378:metabolism* / Q000502:physiology; D004260:DNA Repair; D004264:DNA Topoisomerases, Type I / Q000378:metabolism* / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology; D004706:Endodeoxyribonucleases / Q000378:metabolism; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism* / Q000502:physiology; D053484:RecQ Helicases / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C501527:RMI1 protein, human; C533196:RMI2 protein, human; D004247:DNA; D004706:Endodeoxyribonucleases; C097151:Bloom syndrome protein; D004265:DNA Helicases; C509908:DNA2 protein, human; D053484:RecQ Helicases; D004264:DNA Topoisomerases, Type I