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Sequence-specific DNA breaks produced by triplex-directed decay of iodine-125
1Department of Nuclear Medicine, Clinical Center, National Institutes of Health, Bethesda, MD 20892-1180, USA.
Acta Oncologica (Stockholm, Sweden)
|January 1, 1996
Summary
Triplex forming oligonucleotides (TFOs) labeled with iodine-125 (125I) can specifically target DNA sequences. Radioactive decay from bound TFOs induces targeted DNA double-strand breaks, inactivating specific genes.
Area of Science:
- Molecular Biology
- Radiochemistry
- Genetics
Background:
- Triplex forming oligonucleotides (TFOs) offer sequence-specific DNA binding.
- Auger emitters can deliver localized radioactive decay energy.
- Targeted DNA damage is a strategy for gene inactivation.
Purpose of the Study:
- To demonstrate the feasibility of using Auger-emitting TFOs for sequence-specific DNA damage.
- To investigate the induction of DNA double-strand breaks (DSB) by radiolabeled TFOs.
Main Methods:
- A purine-rich 38-mer TFO was labeled with iodine-125 (125I).
- The 125I-labeled TFO was incubated with plasmid DNA containing the human HPRT gene target sequence.
- DNA breaks were analyzed using sequencing gel electrophoresis after 60 days of 125I decay.
Main Results:
- 125I-labeled TFOs induced sequence-specific DSBs in the target HPRT sequence when bound to plasmid DNA.
- No sequence-specific breaks were observed with unbound 125I-labeled TFOs.
- Approximately 25% of plasmid molecules showed DSBs, with 0.3 DSB per decay, localized near the 125I positions.
Conclusions:
- Radiolabeled TFOs can effectively deliver localized DNA damage to specific sequences.
- This approach demonstrates potential for targeted gene inactivation through sequence-specific DNA breaks.