title: Sequence-specific DNA breaks produced by triplex-directed decay of iodine-125.
abstract: Triplex forming oligonucleotides (TFO) labeled with Auger emitters could be ideal vehicles to deliver radioactive-decay energy to specific DNA sequences, causing DNA breaks and, subsequently, inactivation of these sequences. To demonstrate this approach we labeled with 125I (two 125I per molecule on average) a purine-rich 38-mer which forms a stable triplex with a polypurine x polypyrimidine stretch in the human HPRT gene. Decay of 125I in the bound TFO was shown to cause sequence-specific double strand breaks (DSB) in the target HPRT sequence cloned into plasmid DNA. No sequence-specific breaks were observed if 125I-labeled TFO were not bound to the plasmid DNA. After 60 days of decay accumulation (one 125I half-life) approximately a quarter of all plasmid molecules contained sequence-specific DSB, corresponding to 0.3 site-specific DSB per decay. Sequencing gel analysis shows that the DNA breaks are distributed within a few bases of the maxima at those bases opposite to the positions of 125I in the TFO.
authors.affiliation: Department of Nuclear Medicine, Clinical Center, National Institutes of Health, Bethesda, MD 20892-1180, USA.
authors.forename: I G
authors.initials: IG
authors.lastname: Panyutin
authors.forename: R D
authors.initials: RD
authors.lastname: Neumann
mesh_terms: D001483:Base Sequence / Q000528:radiation effects; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D004277:DNA, Single-Stranded / Q000528:radiation effects; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics* / Q000378:metabolism; D007457:Iodine Radioisotopes / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015345:Oligonucleotide Probes / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics / Q000528:radiation effects
chemical_list: D004277:DNA, Single-Stranded; D007457:Iodine Radioisotopes; D015345:Oligonucleotide Probes; D004247:DNA; D007041:Hypoxanthine Phosphoribosyltransferase