Triple-Helix Formation by Oligonucleotides Containing the Three Bases Thymine, Cytosine, and Guanine

• Published in: Proceedings of the National Academy of Sciences - PNAS 1992-09, Vol.89 (18), p.8631-8635
• Main Authors: Giovannangeli, Carine, Rougee, Michel, Garestier, Therese, Thuong, Nguyen T., Helene, Claude
• Format: Article
• Language: English
• Subjects: AIDS/HIV; Analytical, structural and metabolic biochemistry; Base Sequence; Biochemistry; Biological and medical sciences; Chemical bases; Cross-Linking Reagents; Cytosine - chemistry; Deoxyribonucleic acid; DNA; Dna, deoxyribonucleoproteins; DNA, Viral - chemistry; Enzymes; Fundamental and applied biological sciences. Psychology; Furocoumarins - chemistry; Genomes; Guanine - chemistry; HIV; HIV - genetics; human immunodeficiency virus; Hydrogen Bonding; Irradiation; Melting; Molecular Sequence Data; Nucleic Acid Conformation; Nucleic acids; Oligodeoxyribonucleotides - chemistry; Oligonucleotides; Plasmids; Proteins; Psoralens; Structure-Activity Relationship; Thymine - chemistry
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.89.18.8631

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.