Immunologically active lesions induced on double-stranded DNA with ultraviolet

Enhanced ATPase activity in liver cell nuclei induced by administration of mitomycin C to rats

Intraperitoneal administration of mitomycin C (40 micrograms/100 g body weight) to male Wistar rats increased the ATPase activity in hypotonic extracts of liver cell nuclei for 4 days after injection. Partially purified ATPase, obtained by the DEAE-cellulose column chromatography of these extracts, showed a 14 times higher specific activity than that found in normal rat liver nuclei. The enzymatic activity was strongly enhanced by the addition of polynucleotides, especially poly A and poly I, to the assay mixture, but was inhibited by GTP, a chelating agent, heparin and thiol-group inhibitors. Quercetin and oligomycin were less effective, and ouabain showed no inhibitory effect. Mg2+ ions were essential, but neither Ca2+, Na+ nor K+ ions were required for the manifestation of the activity. These characteristic properties of the enzyme are similar to those of a nucleoside triphosphatase found in the nuclear matrix and envelope, suggesting that some energy-providing mechanisms involved in the repair processes of DNA damage or cellular injury are induced by mitomycin C administration.

Recent aspects of the photochemistry of nucleic acids and related model compounds

This survey focuses on recent developments in the far ultraviolet photochemistry of nucleic acids and related model compounds. The photoproducts discussed are the cyclobutidipyrimidines, the pyrimidine-pyrimidone adducts, the purine-pyrimidine adducts and the addition products of amino acids to pyrimidine bases. The specific aspects of the high-intensity laser photochemistry of nucleic acid components are also briefly reviewed.

Measurement of ultraviolet light-induced photolesions in mammalian DNA by microELISA

A sensitive microELISA was developed for titration of anti-UV-DNA antisera and measurement of photolesions in DNA using UV-irradiated DNA as antigen coupled to the wells of microtitre plates. Efficient and reproducible immobilization of the antigen required precoating of the plates with poly(L-lysine). Antisera from 2 rabbits immunized with UVdsDNA recognized specifically thymine dimer associated lesions. The antiserum from one animal was used to probe photodamage in DNA. Lesions induced by an irradiation dose as small as 2.5 J/m2 could be detected.

Application of the Farr assay to the analysis of antibodies specific for UV irradiated DNA

In order to determine the optimum conditions for reactivity in the ammonium sulphate precipitation (Farr) assay was have studied the DNA binding properties of two antibodies raised against ultraviolet single stranded DNA (UVssDNA) complexed with methylated bovine serum albumin. In general the buffer composition, pH, temperature, and ionic strength conditions described for binding to undamaged DNA were found to be appropriate for binding to UV-irradiated DNA. However, some differences in detail were noted which indicate the necessity for checking the physical conditions of binding of individual antibodies. Mouse monoclonal antibody and rabbit polyclonal antisera bound to UVssDNA very rapidly, even when DNA and ammonium sulphate were added simultaneously, whereas this procedure prevented binding of rabbit antisera to UV-irradiated double stranded DNA. Incubation at 45 degrees C for 30 min inhibited binding by mouse antibody, and incubation at 37 degrees C for 60 min caused reversible dissociation of the DNA-antibody complex. The optimised Farr assay was used to define the antigen specificities of the antibodies. The mouse antibody specifically bound to UVssDNA, but not to ssDNA, double stranded (ds) DNA, or UVdsDNA, whereas the rabbit antisera bound to UVssDNA, ssDNA or UVdsDNA, but not dsDNA. The extent of binding of the mouse antibody was dependent on the UV dose to the antigen, as well as the antigen concentration, indicating that the Farr assay can form the basis of a quantitative assay for photoproducts in DNA.