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SELECTIVE DNA THYMINE DIMERIZATION DURING UVA IRRADIATION IN THE PRESENCE OF A SATURATED PYRIDOPSORALEN
Author(s) -
Guillo LidiaAndreu,
Blais Jocelyne,
Vigny Paul,
Spassky Annick
Publication year - 1995
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1995.tb08617.x
Subject(s) - cyclobutane , pyrimidine dimer , thymine , dna , chemistry , footprinting , psoralen , stereochemistry , photosensitizer , photochemistry , dna damage , biochemistry , ring (chemistry) , organic chemistry , base sequence
Abstract— It has been recently shown that UVA (320–400 nm) irradiation of DNA in the presence of pyridopsoralens induces the formation of thymine cyclobutane dimers in addition to monoadducts. In this work, we measured the potency of a saturated pyridopsoralen to photosensitize DNA, despite its inability to covalently attach to DNA. First, from spectroscopic fluorescence measurements, we have shown that both analogs, saturated and unsaturated pyridopsoralens, namely 4′,5′‐dihydro‐7‐methyl‐pyrido[3,4‐clpsoralen (DH‐MePyPs) and 7‐methylpyrido[3,4‐c]psoralen, exhibit a similar global affinity for DNA. Secondly, we demonstrated, by footprinting experiments, that exposure of a DNA sequence to 365 nm UV radiation in the presence of DH‐MePyPs results in selective cyclobutane thymine dimerization. Thymines located in the immediate proximity of the 5′‐TA‐3′ step are exclusively affected and the frequency of this photoprocess depends on flanking sequences. We thus probe a selective thymine dimer photosensitizer. Results are discussed in terms of drug affinity and physical properties of the helix at the binding site.