Photosensitized DNA damage in human cells is localized in chromatin sensitive to DNAse I digestion.
Human NHIK 3025 cells were sensitized to light by incubation with Photofrin II (PII) and aluminum phthalocyanine tetrasulphonate (AlPCS4). Light exposure of sensitized cells at 1 degree C induced DNA strand breaks causing unwinding of DNA in alkali. Subsequent to light exposure, cells were treated with deoxyribonuclease I (DNAse I) which produces DNA strand breaks in active chromatin. The combination of photo-damage, killing > 95% of the cells, and treatment with DNAse I caused the same degree of DNA unwinding as DNAse I treatment alone. This was not the case for X-irradiation. Thus, the photosensitized DNA strand breaks were selectively induced in or close to DNAse I-sensitive sites.
Kvam
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Department of Biophysics, Norwegian Radium Hospital, Montebello, Oslo.
D002478:Cells, Cultured; D002843:Chromatin / Q000201:enzymology / Q000378:metabolism* / Q000528:radiation effects*; D004247:DNA / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects*; D004249:DNA Damage; D003850:Deoxyribonuclease I / Q000378:metabolism*; D017323:Dihematoporphyrin Ether / Q000494:pharmacology*; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D007700:Kinetics; D009942:Organometallic Compounds / Q000494:pharmacology*; D010777:Photochemistry; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*
D002843:Chromatin; D007211:Indoles; D009942:Organometallic Compounds; D011838:Radiation-Sensitizing Agents; C048577:aluminum tetrasulfophthalocyanine; D004247:DNA; D017323:Dihematoporphyrin Ether; D003850:Deoxyribonuclease I