Gene Specific Damage and Repair after Treatment of Cells with UV and Chemotherapeutical Agents

  • Vilhelm A. Bohr
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 283)


We have previously demonstrated preferential DNA repair of active genes in mammalian cells. The methodology involves the use of a specific endonuclease or other more direct approaches to create nicks at sites of damage followed by quantitative Southern analysis and probing for specific genes. Initially, we used pyrimidine dimer specific endonuclease to detect pyrimidine dimers after UV irradiation. We now also use the bacterial enzyme ABC excinuclease to examine the DNA damage and repair of a number of adducts other than pyrimidine dimers in specific genes. We can detect gene specific alkylation damage by creating nicks via depurination and alkaline hydrolysis. In our assay for preferential repair, we compare the efficiency of repair in the DHFR gene to that in the 3′ flanking, non-coding region to the gene. In CHO cells, UV induced pyrimidine dimers are efficiently repaired from the active DHFR gene, but not from the inactive region. We have demonstrated that the 6–4 photoproducts are also preferentially repaired and that they are removed faster from the regions studied than pyrimidine dimers. Using similar approaches, we find that DNA adducts and crosslinks caused by cisplatinum are preferentially repaired in the active gene compared to the inactive regions and to the inactive c-fos oncogene. Also, nitrogen mustard and methylnitrosurea damage is preferentially repaired whereas dimethyisuiphate damage is not. NAAAF adducts do not appear to be preferentially repaired in this sytem.

In an attempt to correlate the repair events in specific regions with genomic translocations we have studied DNA damage and repair in the murine c-myc oncogene after UV damage and in the human c-myc after alkylation damage; these results will be discussed.


Chinese Hamster Ovary Cell Chinese Hamster Ovary Nitrogen Mustard Pyrimidine Dimer DHFR Gene 
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Copyright information

© Plenum Press, New York 1991

Authors and Affiliations

  • Vilhelm A. Bohr
    • 1
  1. 1.Laboratory of Molecular Pharmacology Division of Cancer Treatment National Cancer InstituteNIHBethesdaUSA

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