title: Characterization of DNA G-quadruplex species forming from C9ORF72 G4C2-expanded repeats associated with amyotrophic lateral sclerosis and frontotemporal lobar degeneration.
abstract: The G4C2 hexanucleotide repeat expansion, located in the first intron of the C9ORF72 gene, represents a major genetic hallmark of amyotrophic lateral sclerosis and frontotemporal lobar degeneration. Several hypotheses have been proposed on how the transcribed repeat RNA leads to the development of amyotrophic lateral sclerosis and frontotemporal lobar degeneration. However, despite their importance, factors affecting the transcription of expanded-repeat RNA are not well known. As transcription is dependent on the DNA containing the expanded repeats, it is crucial to understand its structure. G-quadruplexes are known to affect expression on the level of DNA, therefore whether they form on the expanded-repeat DNA constitutes an important biological question. Using nuclear magnetic resonance and circular dichroism spectroscopy we show that DNA G4C2 with varying number of repeats d(G4C2)n form planar guanine quartets characteristic of G-quadruplexes. Additionally, we show DNA G-quadruplexes can form inter- and intra-molecularly in either parallel or anti-parallel orientation, based on d(G4C2) sequence length. This potential structural heterogeneity of longer disease-relevant repeats should therefore be taken into account when studying their role in disease pathogenesis.
authors.affiliation: Slovenian NMR Centre, National Institute of Chemistry, Ljubljana, Slovenia; EN-FIST Center of Excellence, Ljubljana, Slovenia.
authors.forename: Primož
authors.initials: P
authors.lastname: Šket
authors.affiliation: Department of Biotechnology, Jozef Stefan Institute, Ljubljana, Slovenia.
authors.forename: Jure
authors.initials: J
authors.lastname: Pohleven
authors.affiliation: Department of Biotechnology, Jozef Stefan Institute, Ljubljana, Slovenia; Biomedical Research Institute BRIS, Ljubljana, Slovenia.
authors.forename: Anja
authors.initials: A
authors.lastname: Kovanda
authors.affiliation: Department of Biotechnology, Jozef Stefan Institute, Ljubljana, Slovenia.
authors.forename: Maja
authors.initials: M
authors.lastname: Štalekar
authors.affiliation: Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia.
authors.forename: Vera
authors.initials: V
authors.lastname: Župunski
authors.affiliation: Slovenian NMR Centre, National Institute of Chemistry, Ljubljana, Slovenia.
authors.forename: Matja
authors.initials: M
authors.lastname: Zalar
authors.affiliation: Slovenian NMR Centre, National Institute of Chemistry, Ljubljana, Slovenia; EN-FIST Center of Excellence, Ljubljana, Slovenia; Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia. Electronic address: janez.plavec@ki.si.
authors.forename: Janez
authors.initials: J
authors.lastname: Plavec
authors.affiliation: Department of Biotechnology, Jozef Stefan Institute, Ljubljana, Slovenia; Biomedical Research Institute BRIS, Ljubljana, Slovenia. Electronic address: boris.rogelj@ijs.si.
authors.forename: Boris
authors.initials: B
authors.lastname: Rogelj
mesh_terms: D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics*; D000073885:C9orf72 Protein; D002942:Circular Dichroism; D004247:DNA / Q000235:genetics; D042622:DNA Repeat Expansion / Q000235:genetics*; D057174:Frontotemporal Lobar Degeneration / Q000235:genetics*; D054856:G-Quadruplexes; D006801:Humans; D007438:Introns / Q000235:genetics; D009682:Magnetic Resonance Spectroscopy; D011506:Proteins / Q000235:genetics*; D012313:RNA / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D000073885:C9orf72 Protein; C568651:C9orf72 protein, human; D011506:Proteins; D012313:RNA; D004247:DNA
keywords: Amyotrophic lateral sclerosis; Chromosome 9 open reading frame 72; Expanded hexanucleotide repeats; Frontotemporal lobar degeneration; G-quadruplex