title: Effects of actinomycin D on localization of acridine orange chromatin interaction complex in rat astrocytoma C6 cells.
abstract: The purpose of this study was to examine the effects of actinomycin D on localization of acridine orange (AO) binding to DNA in rat astrocytoma C6 cells and to discuss briefly the significance of AO chromatin interaction products. Actinomycin D markedly inhibited 3H-uridine incorporation into RNA and the percentage of AO positive cells was reduced to approximately 40% of that of the untreated control cells, whereas no distinct decrease of 3H-thymidine incorporation was induced by actinomycin D. Electron microscopic radioautography combined with the AO ultracytochemistry revealed that silver grains indicating binding of 3H-actinomycin D are located mostly over the euchromatin portion near the segregated nucleolus and heterochromatin and that no or only a few AO chromatin complex was found in nuclei labeled heavily with 3H-actinomycin D. These results of the present study together with the results of the previous studies seem to indicate that AO might selectively bind to active or derepressed DNA template sites for DNA dependent RNA polymerase in the euchromatin portion of the cell nucleus.
mesh_terms: D000165:Acridine Orange / Q000378:metabolism*; D000818:Animals; D001254:Astrocytoma / Q000378:metabolism* / Q000648:ultrastructure; D001345:Autoradiography; D001665:Binding Sites; D002478:Cells, Cultured; D002843:Chromatin / Q000187:drug effects* / Q000378:metabolism; D004273:DNA, Neoplasm / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology*; D022041:Euchromatin; D006651:Histocytochemistry; D008854:Microscopy, Electron; D051381:Rats
chemical_list: D002843:Chromatin; D004273:DNA, Neoplasm; D022041:Euchromatin; D003609:Dactinomycin; D000165:Acridine Orange