title: Triple-helix formation by oligonucleotides containing the three bases thymine, cytosine, and guanine.
abstract: A homopurine-homopyrimidine sequence of human immunodeficiency virus (HIV) proviral DNA was chosen as a target for triple-helix-forming oligonucleotides. An oligonucleotide containing three bases (thymine, cytosine, and guanine) was shown to bind to its target sequence under physiological conditions. This oligonucleotide is bound in a parallel orientation with respect to the homopurine sequence. Thymines recognize A.T base pairs to form T.A.T base triplets and guanines recognize a run of G.C base pairs to form G.G.C base triplets. A single 5-methylcytosine was shown to stabilize the triple helix when incorporated in a stretch of thymines; it recognizes a single G.C base pair in a run of A.T base pairs. These results provide some of the rules required for choosing the more appropriate oligonucleotide sequence to form a triple helix at a homopurine-homopyrimidine sequence of duplex DNA. A psoralen derivative attached to the oligonucleotide containing thymine, 5-methylcytosine, and guanine was shown to photoinduce cross-linking of the two DNA strands at the target sequence in a plasmid containing part of the HIV proviral DNA sequence. Triplex formation and cross-linking were monitored by inhibition of Dra I restriction enzyme cleavage. The present results provide a rational basis for the development of triplex-forming oligonucleotides targeted to specific sequences of the HIV provirus integrated in its host genome.
authors.affiliation: Laboratoire de Biophysique, Institut National de la Santé et de la Recherche Médicale U. 201, Centre National de la Recherche Scientifique, Paris, France.
authors.forename: C
authors.initials: C
authors.lastname: Giovannangéli
authors.forename: M
authors.initials: M
authors.lastname: Rougée
authors.forename: T
authors.initials: T
authors.lastname: Garestier
authors.forename: N T
authors.initials: NT
authors.lastname: Thuong
authors.forename: C
authors.initials: C
authors.lastname: Hélène
mesh_terms: D001483:Base Sequence; D003432:Cross-Linking Reagents; D003596:Cytosine / Q000737:chemistry; D004279:DNA, Viral / Q000737:chemistry; D011564:Furocoumarins / Q000737:chemistry; D006147:Guanine / Q000737:chemistry; D006678:HIV / Q000235:genetics; D006860:Hydrogen Bonding; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D013329:Structure-Activity Relationship; D013941:Thymine / Q000737:chemistry
chemical_list: D003432:Cross-Linking Reagents; D004279:DNA, Viral; D011564:Furocoumarins; D009838:Oligodeoxyribonucleotides; D006147:Guanine; D003596:Cytosine; D013941:Thymine