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A DNA binding protein from human cells specific for non-dimer damage in UV-irradiated DNA
117 19 R.S. Feldberg and L. Grossman, Dept. of Biology, Tufts University, Medford, Mass. 02155 and Dept. of Biochemical and Biophysical Sciences, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland 21205 (U.S.A.)
A DNA binding protein from human cells specific for non-dimer damage in UVirradiated DNA A DNA binding protein specific for ultraviolet-irradiated DNA has been purified from human placenta. The binding preparation is free of exonuclease, polymerase, endonuclease and N-glycosidase activity. The binding activity is salt dependent and is specific for double-stranded UV- or X-irradiated DNA. The protein shows maximal binding with relatively low doses of UV-irradiation (200 J/m 2 of 254 nm light with q)X-174 RFI DNA). DNA in which the pyrimidine dimers have been monomerized by the action of photolyase {photoreactivating enzyme) remains an effective substrate for the binding protein, suggesting that the protein recognizes photoproducts other than pyrimidine dimers. This is supported by the finding that DNA irradiated under conditions which introduce only pyrimidine dimers is not a substrate for the binding protein. Examination of three of the Xeroderma pigmentosum complementation groups has revealed no deficiency in this binding activity.
2O B.W. Fox and D.G. Poppitt, Paterson Laboratories, Christie Hospital and Holt Radium Institute, Manchester M20 9BX {England)
Methylene dimethane sulphonate (MDMS) resistance and the nature of damage and repair in DNA It has not been possible to demonstrate a covalent interaction of methylene dimethane sulphonate (MDMS) with DNA. However, thermal hyperchromicity measurements of DNA in the presence of MDMS suggest that a non covalent association occurs which allows for (a) a rapid, co-operative denaturation at lower tm values and (b) a pre-transitional hypochromicity which is GC dependent. Both these effects disappear after dialysis of the treated DNA. Yoshida Sarcoma DNA's, sensitivity and resistance to MDMS (and UV), show that a difference in the level of GC sequences may occur. Hybridization studies with [3H]poly C confirms that there is an approx. 17% increase of GC sequences in the DNA of the resistant tumour line.
A DNA binding protein from human cells specific for non-dimer damage in UVirradiated DNA A DNA binding protein specific for ultraviolet-irradiated DNA has been purified from human placenta. The binding preparation is free of exonuclease, polymerase, endonuclease and N-glycosidase activity. The binding activity is salt dependent and is specific for double-stranded UV- or X-irradiated DNA. The protein shows maximal binding with relatively low doses of UV-irradiation (200 J/m 2 of 254 nm light with q)X-174 RFI DNA). DNA in which the pyrimidine dimers have been monomerized by the action of photolyase {photoreactivating enzyme) remains an effective substrate for the binding protein, suggesting that the protein recognizes photoproducts other than pyrimidine dimers. This is supported by the finding that DNA irradiated under conditions which introduce only pyrimidine dimers is not a substrate for the binding protein. Examination of three of the Xeroderma pigmentosum complementation groups has revealed no deficiency in this binding activity.
2O B.W. Fox and D.G. Poppitt, Paterson Laboratories, Christie Hospital and Holt Radium Institute, Manchester M20 9BX {England)
Methylene dimethane sulphonate (MDMS) resistance and the nature of damage and repair in DNA It has not been possible to demonstrate a covalent interaction of methylene dimethane sulphonate (MDMS) with DNA. However, thermal hyperchromicity measurements of DNA in the presence of MDMS suggest that a non covalent association occurs which allows for (a) a rapid, co-operative denaturation at lower tm values and (b) a pre-transitional hypochromicity which is GC dependent. Both these effects disappear after dialysis of the treated DNA. Yoshida Sarcoma DNA's, sensitivity and resistance to MDMS (and UV), show that a difference in the level of GC sequences may occur. Hybridization studies with [3H]poly C confirms that there is an approx. 17% increase of GC sequences in the DNA of the resistant tumour line.