title: Repair of benzo(a)pyrene diol epoxide- and UV-induced DNA damage in dihydrofolate reductase and adenine phosphoribosyltransferase genes of CHO cells.
abstract: Using Uvr proteins we have quantified benzo(a)pyrene diol epoxide (BPDE)-DNA adduct formation and repair at the dihydrofolate reductase (DHFR) and adenine phosphoribosyltransferase (APRT) genes in two Chinese hamster ovary cell lines: B-11 cells, which are 50-fold amplified for DHFR, and AT3-2 cells, which are diploid for DHFR. We have found that: 1) BPDE-DNA adduct formation in different regions of the DHFR gene is proportional to the concentration of BPDE. 2) There is no significant difference in the repair of BPDE-DNA adducts between the coding and noncoding regions in either amplified or nonamplified DHFR gene domains. 3) Repair in the nonamplified DHFR gene is more efficient (30-40%) than in the amplified DHFR genes. 4) There are no significant differences of repair in the transcribed or nontranscribed strands of the DHFR gene. 5) BPDE-DNA adduct formation and repair in the APRT gene in B-11 and AT3-2 cells are the same. These results contrast those for the repair of cyclobutane pyrimidine dimers, which occurs preferentially in the transcribed strand of the DHFR gene and in which gene amplification appears to play no role.
authors.affiliation: University of Texas M. D. Anderson Cancer Center, Science Park-Research Division, Smithville 78957.
authors.forename: M S
authors.initials: MS
authors.lastname: Tang
authors.forename: A
authors.initials: A
authors.lastname: Pao
authors.forename: X S
authors.initials: XS
authors.lastname: Zhang
mesh_terms: D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000633:toxicity*; D000228:Adenine Phosphoribosyltransferase / Q000235:genetics*; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004247:DNA / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair; D043224:Deoxyribonuclease (Pyrimidine Dimer); D004706:Endodeoxyribonucleases; D029968:Escherichia coli Proteins; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*; D014158:Transcription, Genetic; D014466:Ultraviolet Rays
chemical_list: D029968:Escherichia coli Proteins; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D004247:DNA; D013762:Tetrahydrofolate Dehydrogenase; D000228:Adenine Phosphoribosyltransferase; D004706:Endodeoxyribonucleases; C036385:endodeoxyribonuclease uvrABC; D043224:Deoxyribonuclease (Pyrimidine Dimer)