Ultra-violet-light-induced DNA-to-protein Cross-linking in HeLa Cells

Abstract

The extractability of DNA from u.v.-irradiated HeLa cells following lysis is an inverse function of the u.v.-dose. The effect was examined immediately after exposures ranging from 500 ergs/mm 2 to 3000 ergs/mm 2 , and the cells were irradiated either at room temperature (22c) or in cold (4°c). The unextracted DNA was recovered from the protein fraction with 0.5 per cent trypsin solution. Dose-response curves show that the magnitude of the effect increased linearly with dose, and the amount of DNA recovered from irradiated cells decreased for about 1 per cent for every 100 ergs/mm 2 of u.v. light for cells exposed at room temperature. The effect is twice as large, when the cells are irradiated in cold. The amount of DNA cross-linked to proteins remained unchanged from 0 up to 10 hours after exposure, i.e. for as long as the experiments were carried out.

Experimental Ultraviolet Light-Carcinogenesis

“…It has been proposed that the lethal effect of UV radiation may depend on the formation of cross-links between DNA and protein (Smith, 1964a(Smith, , 1967(Smith, , 1968Smith, Hodgkins and OLeary, 1966;Smith and OLeary, 1967;Habazin and Han, 1970;Smets and Cornelis, 1971;Han, Korbelik and Ban, 1975). The presence of DNA-protein cross-links was inferred from a reduction in extractability of DNA from cell lysates and from the finding that DNA extractability is restored by treatment of the lysates with trypsin (Alexander and Moroson, 1962;Smith, 1962).…”

Conversion of non‐covalent interactions in nucleoproteins into covalent bonds: UV‐induced formation of polynucleotide—protein crosslinks in bacteriophage Sd virions

“…Polynucleotide-protein links are well known to arise as the result of ultraviolet (UV) irradiation of viruses and cells (see, for example, [2][3][4][5][6]. Among the underlying reactions could be the interactions of the excited uracil and thymine nuclei with amino acid residues [7][8][9][10][11][12][13][14].…”

Uv Induced Dna‐protein Cross‐links in Vitro and in Vivo

“…Mammalian (eucaryotic) cells, in general, represent a suitable model for the cross-linking reaction primarily due to the high concentration of basic amino acids in histones which might facilitate the occurrence of UV-induced histoneDNA covalent bonds. Han, working with his group in Zagreb as well as in the Argonne Laboratory, studied the general features of UV (254 nm) induced DNA-protein cross-links in asynchronous [9] and synchronized [lo] HeLa cells. Cross-linking was demonstrated by the detection of unextractable DNA in irradiated cells.…”