title: Stability of telomeric G-quadruplexes.
abstract: In most eukaryotes, telomeric DNA consists of repeats of a short motif that includes consecutive guanines and may hence fold into G-quadruplexes. Budding yeasts have telomeres composed of longer repeats and show variation in the degree of repeat homogeneity. Although telomeric sequences from several organisms have been shown to fold into G-quadruplexes in vitro, surprisingly, no study has been dedicated to the comparison of G-quadruplex folding and stability of known telomeric sequences. Furthermore, to our knowledge, folding of yeast telomeric sequences into intramolecular G-quadruplexes has never been investigated. Using biophysical and biochemical methods, we studied sequences mimicking about four repetitions of telomeric motifs from a variety of organisms, including yeasts, with the aim of comparing the G-quadruplex folding potential of telomeric sequences among eukaryotes. G-quadruplex folding did not appear to be a conserved feature among yeast telomeric sequences. By contrast, all known telomeric sequences from eukaryotes other than yeasts folded into G-quadruplexes. Nevertheless, while G(3)T(1-4)A repeats (found in a variety of organisms) and G(4)T(2,4) repeats (found in ciliates) folded into stable G-quadruplexes, G-quadruplexes formed by repetitions of G(2)T(2)A and G(2)CT(2)A motifs (found in many insects and in nematodes, respectively) appeared to be in equilibrium with non-G-quadruplex structures (likely hairpin-duplexes).
authors.affiliation: INSERM, U565, Acides Nucléiques: Dynamique, Ciblage et Fonctions Biologiques, Muséum National d'Histoire Naturelle, CNRS, UMR7196, Département de Régulations, Développement et Diversité Moléculaire, 43 rue Cuvier, CP26, Paris Cedex 5 -75231, France.
authors.forename: Phong Lan Thao
authors.initials: PL
authors.lastname: Tran
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Mergny
authors.forename: Patrizia
authors.initials: P
authors.lastname: Alberti
mesh_terms: D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D031541:Fluorescence Resonance Energy Transfer; D054856:G-Quadruplexes; D009691:Nucleic Acid Denaturation; D016615:Telomere / Q000737:chemistry*; D013696:Temperature