Effects of camptothecin, an inhibitor of DNA topoisomerase I on ribosomal gene structure and function in TG cells.
The effects of camptothecin treatment and topoisomerase I inhibition on ribosomal gene structure and function were investigated in TG cells, a human tumour cell line. 90- and 180-min treatments with 25 microM camptothecin resulted in an increased DNA fragmentation and decreased activity of topoisomerase I in cell extracts. After 180-min treatment, the incorporation of labelled uridine into total cell RNA was reduced to 39% and the ribosomal RNA synthesis to 10%, as compared to values of control cells. At the ultrastructural level, the nucleolar components appeared to be segregated; after selective DNA staining, with osmium-amine complex, a part of the nucleolar chromatin of treated cells showed the presence of thin, extended DNA filaments, superimposable to those present in control cells.
Farabegoli
F
F
Dipartimento di Patologia Sperimentale, Università di Bologna, Italy.
Govoni
M
M
Novello
F
F
D002166:Camptothecin / Q000494:pharmacology*; D002466:Cell Nucleolus / Q000187:drug effects* / Q000648:ultrastructure; D002843:Chromatin / Q000187:drug effects / Q000648:ultrastructure; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000187:drug effects*; D004275:DNA, Ribosomal / Q000187:drug effects*; D003864:Depression, Chemical; D005796:Genes / Q000187:drug effects; D006801:Humans; D012334:RNA, Neoplasm / Q000096:biosynthesis / Q000235:genetics*; D012335:RNA, Ribosomal / Q000096:biosynthesis / Q000235:genetics*; D059004:Topoisomerase I Inhibitors; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure
D002843:Chromatin; D004273:DNA, Neoplasm; D004275:DNA, Ribosomal; D012334:RNA, Neoplasm; D012335:RNA, Ribosomal; D059004:Topoisomerase I Inhibitors; D002166:Camptothecin