title: The intrinsically disordered amino-terminal region of human RecQL4: multiple DNA-binding domains confer annealing, strand exchange and G4 DNA binding.
abstract: Human RecQL4 belongs to the ubiquitous RecQ helicase family. Its N-terminal region represents the only homologue of the essential DNA replication initiation factor Sld2 of Saccharomyces cerevisiae, and also participates in the vertebrate initiation of DNA replication. Here, we utilized a random screen to identify N-terminal fragments of human RecQL4 that could be stably expressed in and purified from Escherichia coli. Biophysical characterization of these fragments revealed that the Sld2 homologous RecQL4 N-terminal domain carries large intrinsically disordered regions. The N-terminal fragments were sufficient for the strong annealing activity of RecQL4. Moreover, this activity appeared to be the basis for an ATP-independent strand exchange activity. Both activities relied on multiple DNA-binding sites with affinities to single-stranded, double-stranded and Y-structured DNA. Finally, we found a remarkable affinity of the N-terminus for guanine quadruplex (G4) DNA, exceeding the affinities for other DNA structures by at least 60-fold. Together, these findings suggest that the DNA interactions mediated by the N-terminal region of human RecQL4 represent a central function at the replication fork. The presented data may also provide a mechanistic explanation for the role of elements with a G4-forming propensity identified in the vicinity of vertebrate origins of DNA replication.
authors.affiliation: Research Group Biochemistry, Leibniz Institute for Age Research-Fritz Lipmann Institute, Beutenbergstrasse 11, D-07745 Jena, Germany.
authors.forename: Heidi
authors.initials: H
authors.lastname: Keller
authors.affiliation: Research Group Biochemistry, Leibniz Institute for Age Research-Fritz Lipmann Institute, Beutenbergstrasse 11, D-07745 Jena, Germany.
authors.forename: Kristin
authors.initials: K
authors.lastname: Kiosze
authors.affiliation: Research Group Biochemistry, Leibniz Institute for Age Research-Fritz Lipmann Institute, Beutenbergstrasse 11, D-07745 Jena, Germany.
authors.forename: Juliane
authors.initials: J
authors.lastname: Sachsenweger
authors.affiliation: Research Group Biomolecular NMR Spectroscopy, Leibniz Institute for Age Research-Fritz Lipmann Institute, Beutenbergstrasse 11, D-07745 Jena, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Haumann
authors.affiliation: Research Group Biomolecular NMR Spectroscopy, Leibniz Institute for Age Research-Fritz Lipmann Institute, Beutenbergstrasse 11, D-07745 Jena, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Ohlenschläger
authors.affiliation: Department of Biology, University of Eastern Finland, PO Box 111, FI-80101 Joensuu, Finland.
authors.forename: Tarmo
authors.initials: T
authors.lastname: Nuutinen
authors.affiliation: Institute of Biomedicine, University of Eastern Finland, PO Box 1627, FI-70211 Kuopio, Finland.
authors.forename: Juhani E
authors.initials: JE
authors.lastname: Syväoja
authors.affiliation: Research Group Biomolecular NMR Spectroscopy, Leibniz Institute for Age Research-Fritz Lipmann Institute, Beutenbergstrasse 11, D-07745 Jena, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Görlach
authors.affiliation: Research Group Biochemistry, Leibniz Institute for Age Research-Fritz Lipmann Institute, Beutenbergstrasse 11, D-07745 Jena, Germany Center for Molecular Biomedicine, Friedrich-Schiller University, Jena, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Grosse
authors.affiliation: Research Group Biochemistry, Leibniz Institute for Age Research-Fritz Lipmann Institute, Beutenbergstrasse 11, D-07745 Jena, Germany Faculty of Biochemistry and Molecular Medicine, PO Box 5000, FI-90014 University of Oulu, Finland pospiech@fli-leibniz.de.
authors.forename: Helmut
authors.initials: H
authors.lastname: Pospiech
mesh_terms: D001665:Binding Sites; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry; D054856:G-Quadruplexes; D006801:Humans; D064267:Intrinsically Disordered Proteins / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D053484:RecQ Helicases / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D064267:Intrinsically Disordered Proteins; D004247:DNA; C506731:RECQL4 protein, human; D053484:RecQ Helicases