title: Differential repair of polycyclic aromatic hydrocarbon DNA adducts from an actively transcribed gene.
abstract: Polycyclic aromatic hydrocarbons (PAHs) are carcinogens with varying potencies. These compounds are metabolized to diol epoxides that react to form DNA adducts. Nucleotide excision repair is a critical cellular defense against these bulky DNA adducts which, if not repaired, can lead to mutations and the initiation of cancer. The structural features of the PAH-adducts play a role in differential repair of these adducts by the global genomic repair subpathway of nucleotide excision repair. DNA adducts derived from the PAHs containing bay-regions are repaired more rapidly than adducts derived from PAHs containing fjord-regions. We have employed the host cell reactivation assay to examine the rate of repair of these adducts in an actively transcribing gene. The pGL3 plasmid containing a luciferase gene was damaged with diol epoxides of benzo[a]pyrene (B[a]P-DE), dibenzo[a,l]pyrene (DB[a,l]P-DE), benzo[g]chrysene (B[g]Ch-DE), and benzo[c]phenanthrene (B[c]Ph-DE). The plasmids were transfected into B-lymphocytes with normal repair capacity as well as lymphocytes derived from patients with the XP-A, XP-C and CS-B syndromes. We found that XPA cells were able to transcribe slowly past B[g]Ch-adducts but not the other PAHs. Using the amount of luciferase produced as a measure of DNA repair, we found that the relative rates of repair in the actively transcribing luciferase gene was B[a]P-DE>DB[a,l]P-DE, B[g]Ch-DE, >B[c]Ph-DE in repair proficient and XP-C cells. These results indicate that the abilities to transcribe past and to repair the PAH adducts are dependent on different structural features of the DNA adducts.
authors.affiliation: Department of Biochemistry & Molecular Biology, Pennsylvania State University, 500 University Drive, Hershey, PA 17033, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhong
authors.forename: Shantu
authors.initials: S
authors.lastname: Amin
authors.forename: Philip
authors.initials: P
authors.lastname: Lazarus
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Spratt
mesh_terms: D002461:Cell Line, Transformed; D018736:DNA Adducts; D004260:DNA Repair; D006801:Humans; D011083:Polycyclic Compounds; D014158:Transcription, Genetic
chemical_list: D018736:DNA Adducts; D011083:Polycyclic Compounds