title: Inhibition of gene-specific repair of alkylation damage in cells depleted of poly(ADP-ribose) polymerase.
abstract: The role of the enzyme poly(adenosine diphosphate-ribose) polymerase (PADPRP) in DNA repair at the level of the gene was investigated with human HeLa cells in which PADPRP antisense transcripts are inducible with dexamethasone. After such induction, the cellular content of PADPRP is reduced by 90%. DNA damage and its repair was studied in the essential dihydrofolate reductase (DHFR) gene after exposure of the cells to either ultraviolet (UV) irradiation or the alkylating agent nitrogen mustard. The expression of the antisense construct had no effect on gene-specific repair of UV-induced pyrimidine dimers. In contrast, induced antisense cells were deficient in the gene-specific repair of nitrogen mustard-induced lesions. Dexamethasone itself did not inhibit gene-specific repair in control cells. Thus, PADPRP appears to participate in the gene-specific repair of alkylation damage, but not in the repair of UV-induced pyrimidine dimers. Clonal survival assays revealed that cells depleted of PADPRP showed an increased susceptibility to nitrogen mustard, supporting the notion that repair of essential genes is critical for cellular survival.
authors.affiliation: Laboratory of Molecular Genetics, National Institute of Aging, National Institutes of Health, Baltimore, MD 21224.
authors.forename: T
authors.initials: T
authors.lastname: Stevnsner
authors.forename: R
authors.initials: R
authors.lastname: Ding
authors.forename: M
authors.initials: M
authors.lastname: Smulson
authors.forename: V A
authors.initials: VA
authors.lastname: Bohr
mesh_terms: D000478:Alkylation; D002470:Cell Survival / Q000187:drug effects; D004247:DNA / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair / Q000502:physiology*; D003907:Dexamethasone / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D008466:Mechlorethamine / Q000494:pharmacology / Q000633:toxicity; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D011740:Pyrimidine Dimers / Q000378:metabolism; D016372:RNA, Antisense; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics; D014466:Ultraviolet Rays
chemical_list: D011740:Pyrimidine Dimers; D016372:RNA, Antisense; D008466:Mechlorethamine; D003907:Dexamethasone; D004247:DNA; D013762:Tetrahydrofolate Dehydrogenase; D011065:Poly(ADP-ribose) Polymerases