title: "Parallel" and "antiparallel tail-clamps" increase the efficiency of triplex formation with structured DNA and RNA targets.
abstract: Sequence-specific triple-helix structures can be formed by parallel and antiparallel DNA clamps interacting with single-stranded DNA or RNA targets. Single-stranded nucleic acid molecules are known to adopt secondary structures that might interfere with intermolecular interactions. We demonstrate the correlation between a secondary structure involving the target--a stable stem predicted by in silico folding and experimentally confirmed by thermal stability and competition analyses--and an inhibitory effect on triplex formation. We overcame structural impediments by designing a new type of clamp: "tail-clamps". A combination of gel-shift, kinetic analysis, UV thermal melting and thermodynamic techniques was used to demonstrate that tail-clamps efficiently form triple helices with a structured target sequence. The performance of parallel and antiparallel tail-clamps was compared: antiparallel tail-clamps had higher binding efficiencies than parallel tail-clamps both with structured DNA and RNA targets. In addition, the reported triplex-stabilizing property of 8-aminopurine residues was confirmed for tail-clamps. Finally, we discuss the possible use of this improved triplex technology as a new tool for applications in molecular biology.
authors.affiliation: Departament de Genètica Molecular, Institut de Biologia Molecular de Barcelona, Consejo Superior de Investigaciones Científicas, Jordi Girona 18-26, 08034 Barcelona, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Nadal
authors.forename: Ramon
authors.initials: R
authors.lastname: Eritja
authors.forename: Teresa
authors.initials: T
authors.lastname: Esteve
authors.forename: Maria
authors.initials: M
authors.lastname: Pla
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000737:chemistry*; D004277:DNA, Single-Stranded / Q000737:chemistry; D024202:Electrophoretic Mobility Shift Assay; D005821:Genetic Techniques; D007700:Kinetics; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry; D011687:Purines / Q000737:chemistry; D012313:RNA / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D004277:DNA, Single-Stranded; D009841:Oligonucleotides; D011687:Purines; C051802:triplex DNA; D012313:RNA; D004247:DNA