Spatially localized generation of nucleotide sequence-specific DNA damage

Area of Science:

• Photochemistry
• Molecular Biology
• Biophysics

Background:

• Psoralen-DNA photoadducts are formed using psoralen and UV A radiation.
• Two-photon excitation (TPE) offers a lower-energy excitation method for photochemistry.

Purpose of the Study:

• To demonstrate TPE's ability to induce psoralen-DNA photoadducts.
• To achieve spatial localization of DNA damage using TPE.
• To assess the safety and efficacy of psoralen-TPE treatment in cells.

Main Methods:

• Incubating DNA with psoralen-linked triplex-forming oligonucleotides (psoTFOs).
• Irradiating psoTFO-DNA complexes with pulsed 765-nm laser light for TPE.
• Localizing DNA damage in polyacrylamide gels and cultured human fibroblasts.
• Assessing DNA damage via tritium labeling and cell viability assays.

Main Results:

• TPE induced strand-specific psoralen monoadducts in a light dose-dependent manner.
• DNA damage was spatially localized to the rear of a polyacrylamide gel.
• TPE treatment of human fibroblasts with psoralen showed increased DNA adducts without significant toxicity.
• Functional survival assays confirmed no cellular toxicity from psoralen-TPE.

Conclusions:

• TPE can initiate photochemistry to create psoralen-DNA photoadducts with spatial control.
• This technique allows for precise, three-dimensional manipulation of DNA damage.
• Psoralen-TPE holds promise for photochemotherapeutic applications in optically accessible tissues.