ENHANCED PYRIMIDINE DIMER REPAIR IN CULTURED MURINE EPITHELIAL-CELLS TRANSFECTED WITH THE DENV GENE OF BACTERIOPHAGE-T4

The patch size for excision repair of ultraviolet radiation (UV)-induc ed pyrimidine dimers was determined in cultured murine epithelial cell s with normal and enhanced pyrimidine dimer repair capabilities. Cells with enhanced pyrimidine dimer repair were produced by transfecting 3 08 cells with the denV gene of bacteriophage T4; this gene encodes the enzyme endonuclease V. Pyrimidine dimer repair following exposure to UV from an FS-40 sunlamp was determined by micrococcal dimer-specific nuclease digestion and alkaline sucrose ultracentrifugation. Patch siz e was estimated based on the photolytic lability of bromodeoxyuridine- substituted DNA. Excision repair or UV-induced pyrimidine dimers in de nV-transfected 308 cells was enhanced two- to threefold. Production of mRNA from the denV gene in cell lines with enhanced repair was confir med by RNA blotting. In control cells, the patch size for excision rep air of DNA photoproducts was estimated to be 34 nucleotides per photop roduct removed; in denV-transfected cells, a smaller average patch siz e of 10-16 nucleotides per photoproduct removed was calculated. Thus, endonuclease V activity appears to alter not only the extent, but also the nature of excision repair in UV-exposed mammalian epithelial cell s.