title: Structural and biochemical characterization of an RNA/DNA binding motif in the N-terminal domain of RecQ4 helicases.
abstract: The RecQ4 helicase belongs to the ubiquitous RecQ family but its exact role in the cell is not completely understood. In addition to the helicase domain, RecQ4 has a unique N-terminal part that is essential for viability and is constituted by a region homologous to the yeast Sld2 replication initiation factor, followed by a cysteine-rich region, predicted to fold as a Zn knuckle. We carried out a structural and biochemical analysis of both the human and Xenopus laevis RecQ4 cysteine-rich regions, and showed by NMR spectroscopy that the Xenopus fragment indeed assumes the canonical Zn knuckle fold, whereas the human sequence remains unstructured, consistent with the mutation of one of the Zn ligands. Both the human and Xenopus Zn knuckles bind to a variety of nucleic acid substrates, with a mild preference for RNA. We also investigated the effect of a segment located upstream the Zn knuckle that is highly conserved and rich in positively charged and aromatic residues, partially overlapping with the C-terminus of the Sld2-like domain. In both the human and Xenopus proteins, the presence of this region strongly enhances binding to nucleic acids. These results reveal novel possible roles of RecQ4 in DNA replication and genome stability.
authors.affiliation: Structural Biology Laboratory, Elettra-Sincrotrone Trieste S.C.p.A., Trieste, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Marino
authors.affiliation: Structural Biology Laboratory, Elettra-Sincrotrone Trieste S.C.p.A., Trieste, Italy.|Dipartimento di Scienze della Vita, Università degli Studi di Trieste, Italy.
authors.forename: Aditya
authors.initials: A
authors.lastname: Mojumdar
authors.affiliation: Biomolecular NMR Unit, Division of Genetics and Cell Biology, S. Raffaele Scientific Institute, Milano, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Zucchelli
authors.affiliation: International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy.
authors.forename: Amit
authors.initials: A
authors.lastname: Bhardwaj
authors.affiliation: International Centre for Genetic Engineering and Biotechnology (ICGEB), Trieste, Italy.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Buratti
authors.affiliation: Structural Biology Laboratory, Elettra-Sincrotrone Trieste S.C.p.A., Trieste, Italy.|Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Vindigni
authors.affiliation: Biomolecular NMR Unit, Division of Genetics and Cell Biology, S. Raffaele Scientific Institute, Milano, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Musco
authors.affiliation: Structural Biology Laboratory, Elettra-Sincrotrone Trieste S.C.p.A., Trieste, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Onesti
mesh_terms: D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D000818:Animals; D006801:Humans; D020125:Mutation, Missense; D019906:Nuclear Magnetic Resonance, Biomolecular; D000072417:Protein Domains; D053484:RecQ Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis
chemical_list: D029867:Xenopus Proteins; C506731:RECQL4 protein, human; D053484:RecQ Helicases