Suppression of dexamethasone-stimulated DNA synthesis in an oncogene construct containing rat cell line by a DNA site-oriented ligand of poly-ADP-ribose polymerase: 6-amino-1,2-benzopyrone.
The cellular inhibitory effects of 6-amino-1,2-benzopyrone (6-ABP), a DNA site-specific ligand of adenosine diphosphoribosyl transferase (ADPRT), were determined in a dexamethasone-sensitive EJ-ras gene construct containing cell line (14C cells). Dexamethasone in vitro transforms these cells to a tumorigenic phenotype and also stimulates cell replication. At a non-toxic concentrations (0.2 mM) 6-ABP treatment of intact cells for 4 days inhibits the dexamethasone-stimulated increment of cellular DNA content, depresses replicative DNA synthesis as assayed by thymidine incorporation to the level of cells that were not exposed to dexamethasone, and in permeabilized cells reduces the dexamethasone-stimulated increase of deoxyribonucleotide incorporation into DNA to the level of untreated cells. In situ pulse labeling of cells pretreated with 6-ABP indicated an inhibition of DNA synthesis at a stage prior to the formation of the 10-kb intermediate species. The drug had no direct effect on cellular DNA polymerases as tested in vitro, and the inhibition of DNA synthesis in permeabilized cells following drug treatment for 4 days was abolished by externally added DNA templates. Neither dexamethasone nor the drug influenced the cellular quantity of ADPRT molecules, tested immunochemically.
Kirsten
E
E
Laboratory for Environmental Toxicology and Chemistry, Romberg Tiburon Center for Environmental Studies, California 94920.
Bauer
P I
PI
Kun
E
E
D000818:Animals; D002461:Cell Line, Transformed; D003374:Coumarins / Q000494:pharmacology*; D004261:DNA Replication / Q000187:drug effects*; D003907:Dexamethasone / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D011905:Genes, ras / Q000235:genetics; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D051381:Rats
D003374:Coumarins; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D003907:Dexamethasone; C067496:6-amino-1,2-benzopyrone