title: Interaction of hnRNP A1 with telomere DNA G-quadruplex structures studied at the single molecule level.
abstract: G-rich telomeric DNA sequences can form G-quadruplex structures. The heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) and a shortened derivative (UP1) are active in telomere length regulation, and it has been reported that UP1 can unwind G-quadruplex structures. Here, we investigate the interaction of hnRNP A1 with G-quadruplex DNA structures containing the human telomere repeat (TTAGGG) by gel retardation assays, ensemble fluorescence energy transfer (FRET) spectroscopy, and single molecule FRET microscopy. Our biochemical experiments show that hnRNP A1 binds well to the G-quadruplex telomeric DNA. Ensemble and single molecule FRET measurements provide further insight into molecular conformation: the telomeric DNA overhang is found to be in a folded state in the absence of hnRNP A1 and to remain predominantly in a compact state when complexed with hnRNP A1. This finding is in contrast to the previously reported crystal structures of UP1-telomere DNA complexes where the DNA oligo within the protein-DNA complex is in a fully open conformation.
authors.affiliation: Interdisciplinary Nanoscience Center, Aarhus University, Denmark.
authors.forename: A C
authors.initials: AC
authors.lastname: Krüger
authors.forename: M K
authors.initials: MK
authors.lastname: Raarup
authors.forename: M M
authors.initials: MM
authors.lastname: Nielsen
authors.forename: M
authors.initials: M
authors.lastname: Kristensen
authors.forename: F
authors.initials: F
authors.lastname: Besenbacher
authors.forename: J
authors.initials: J
authors.lastname: Kjems
authors.forename: V
authors.initials: V
authors.lastname: Birkedal
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D031541:Fluorescence Resonance Energy Transfer; D054856:G-Quadruplexes / Q000187:drug effects; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding; D016615:Telomere / Q000737:chemistry*
chemical_list: D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; C000619656:hnRNPA1 protein, human; D004247:DNA