title: A triple helix obtained by specific recognition of all 4 bases in duplex DNA can adopt a collapsed or an extended form.
abstract: It has been proposed that during homologous recombination promoted by RecA DNA triple helices can be formed between a Watson Crick duplex and a homologous third strand without any sequence constraint. A triple helix, obtained by targeting the d(AGTTAGCATG) sequence containing all 4 bases, in which both homologous strands are oriented in a parallel direction with respect to each other, stabilized by addition of Mn2+ ions has been studied by UV and FTIR spectroscopies. We have characterized the sugar conformations of this triplex. All strands are found to contain S type sugars (C2'endo, B family form). Progressive addition of propidium iodide induces a complete reorientation of the sugar geometry to a N type conformation (C3'endo, A family form). This sugar repuckering is consistent with a conformational transition from a collapsed to an extended DNA triple helical structure.
authors.affiliation: URA CNRS 1430, UFR de médecine, Université Paris-XIII, Bobigny, France.
authors.forename: C
authors.initials: C
authors.lastname: Dagneaux
authors.forename: A K
authors.initials: AK
authors.lastname: Shchyolkina
authors.forename: J
authors.initials: J
authors.lastname: Liquier
authors.forename: V L
authors.initials: VL
authors.lastname: Florentiev
authors.forename: E
authors.initials: E
authors.lastname: Taillandier
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D006801:Humans; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: D004247:DNA