Specific inhibition of pre-ribosomal RNA processing in extracts from the lymphosarcoma cells treated with 5-fluorouracil.
To elucidate the molecular mechanism by which the potent anticancer drug, 5-fluorouracil (5-FUra), inhibits cell proliferation, the effect of its metabolite, 5-fluorouridine triphosphate, on transcription of rat rRNA gene and processing of pre-rRNA was investigated in S-100 extract from the mouse lymphosarcoma cells. The in vitro processing of pre-rRNA substrate synthesized from the T3 promoter occurred at the correct primary processing site. Replacement of UMP with 5-fluorouridine monophosphate in the rRNA substrate did not affect the pre-rRNA processing. Similar result was obtained when coupled transcription-processing was studied. When the coupled reaction was examined using extracts from the cells treated with 5-FUra, rRNA processing was abolished whereas transcription of rRNA gene was unaffected. Treatment of cells with thymidine along with 5-FUra did not reverse the inhibitory effect of the drug on rRNA processing. In contrast to the effect on rRNA processing, treatment of cells with 5-FUra did not impede the 3' end processing of pre-mRNA. These data show that inhibition of pre-rRNA processing is a major mechanism of action of 5-FUra and suggest that the activity and/or synthesis of a trans-acting factor(s) involved in this reaction is altered by the anticancer drug.
Ghoshal
K
K
Department of Pharmacology and Molecular Biology, Chicago Medical School, North Chicago, Illinois 60064.
Jacob
S T
ST
D000818:Animals; D001483:Base Sequence; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002467:Cell Nucleus / Q000737:chemistry / Q000187:drug effects / Q000502:physiology; D004275:DNA, Ribosomal / Q000187:drug effects / Q000235:genetics; D005472:Fluorouracil / Q000378:metabolism / Q000494:pharmacology*; D008228:Lymphoma, Non-Hodgkin / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D012322:RNA Precursors / Q000187:drug effects* / Q000235:genetics* / Q000502:physiology; D012334:RNA, Neoplasm / Q000378:metabolism; D012335:RNA, Ribosomal / Q000187:drug effects* / Q000235:genetics* / Q000502:physiology; D015534:Trans-Activators / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000187:drug effects; D014500:Uracil Nucleotides / Q000378:metabolism / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology
D004275:DNA, Ribosomal; D012322:RNA Precursors; D012334:RNA, Neoplasm; D012335:RNA, Ribosomal; D015534:Trans-Activators; D014500:Uracil Nucleotides; C025635:5-fluorouridine 5'-triphosphate; C016462:5-fluorouridine 5'-phosphate; D005472:Fluorouracil; D014544:Uridine Triphosphate