Coumarin‐Induced DNA Ligation, Rearrangement to DNA Interstrand Crosslinks, and Photorelease of Coumarin Moiety

Abstract

Coumarin moieties react with thymine and cytosine in DNA by photoinduced [2+2] cycloaddition, which allows quantitative DNA interstrand crosslink (ICL) formation. Here, we report the application of coumarin analogues for DNA photoligation and the rearrangement of coumarin-induced ligation to ICL products. Both DNA sequences and the linker units at position 4 of the coumarin moieties affected coumarin-induced DNA photoligation. A flexible linker unit favored DNA ICL formation but led to inefficient photoligation, whereas coumarins without linker units greatly increased DNA photoligation efficiency. DNA photoligation induced by the coumarin moiety was photoswitchable. Ligation products were formed between coumarin and dT or dC upon 350 nm irradiation but reverted to the original single-stranded oligodeoxyribonucleotides (ODNs) upon 254 nm irradiation. Rearrangement of ligated ODNs into ICL products occurred during the switchable (350 nm/254 nm) processes. Additionally, photoinduced cleavage of coumarin 3 occurred with dC-3 cycloadducts upon 254 nm irradiation, which was confirmed by mass spectrometry analysis.

Elucidation of the Dexter‐Type Energy Transfer in DNA by Thymine–Thymine Dimer Formation Using Photosensitizers as Artificial Nucleosides

“…The crosslinks may arise from Paterno–Büchi reactions as shown by Saito et al . or more recently by Peng et al . Careful MS analysis of irradiated DNA1‐0 revealed not only the T T dimerization oligonucleotide product P1, but also the crosslinks of the sensitizer with the fluorescein‐containing oligonucleotides, and of the sensitizer with the fluorescein‐modified and the connecting oligonucleotides (see the Supporting Information).…”

“…They show asmall but suitable absorption in the UV-A range,such that these sensitizers can be excited at 369 nm, independent of DNAexcitation. Thec rosslinks may arise from Paterno-Büchi reactions as shown by Saito et al [18] or more recently by Peng et al [19] Careful MS analysis of irradiated DNA1-0 revealed not only the T<>Tdimerization oligonucleotide product P1, but also the crosslinks of the sensitizer with the fluoresceincontaining oligonucleotides,a nd of the sensitizer with the fluorescein-modified and the connecting oligonucleotides (see the Supporting Information). In order to observe and quantify the T<>Td imer formation process by ac hange of electrophoretic mobility,t he counterstrands to DNA1-n, DNA2-n,a nd DNA3-n lacked the phosphodiester bond between the two adjacent thymidines that are supposed to react with each other.…”

“…In an additional control experiment using aD NA identical to DNA1-0 in which benzophenone was replaced by anormal T, no products with slower mobility than S1 were detected after irradiation. Thec rosslinks may arise from Paterno-Büchi reactions as shown by Saito et al [18] or more recently by Peng et al [19] Careful MS analysis of irradiated DNA1-0 revealed not only the T<>Tdimerization oligonucleotide product P1, but also the crosslinks of the sensitizer with the fluoresceincontaining oligonucleotides,a nd of the sensitizer with the fluorescein-modified and the connecting oligonucleotides (see the Supporting Information). Taken together, there is enough experimental support that P1 is the T<>Td imer product and P2 corresponds to interstrand crosslinking products.…”

DNA photo-cross-linking using a pyranocarbazole-modified oligodeoxynucleotide with a d-threoninol linker

“…Many photo-cross-linkers such as bromouracil 8 and benzophenone 9 have also been reported. Among these, DNA photo-cross-linking via [2 + 2] photocycloaddition by psoralens 5 and coumarins 10 is useful for detection, manipulation, and regulation of nucleic acids because photoreversible manipulation is possible. Compared to the enzymatic method, photo-cross-linking can be used under a wide range of conditions without the addition of reagents.…”

Cancer Hazard Identification Integrating Human Variability: The Case of Coumarin

“…As shown in Table 27, 7-HC was weakly positive in the absence of exogenous metabolic activation in an assay for the induction of CA in CHO cells (Microbiological Associates, 1993, as reviewed by Lake 4 ). Sun et al 219 found that incubation of 7-HC with oligodeoxyribonucleotides and photoirradiation at 350 nm results in the formation of 7-HC-DNA cycloadducts with thymine and cytosine, and DNA interstrand crosslinks. Cycloadduct formation was reversible with photoirradiation at 254 nm, however.…”