Acute effect of 5-fluorouracil on cytoplasmic and nuclear dihydrofolate reductase messenger RNA metabolism.
Studies were completed in C3-L5178Y cells, in which the DNA-coding region for dihydrofolate reductase messenger RNA (DHFR-mRNA) is amplified, to determine the acute effect of 5-fluorouracil (FUra) on DHFR-mRNA metabolism. There was minimal to no effect of 100 microM FUra on total cytoplasmic DHFR-mRNA levels by 6 and 12 h and only a 25% reduction by 24 h. These results contrasted with the nuclear DHFR-mRNA levels which by 6 h following exposure to FUra increased by 80% in a dose-dependent manner. Furthermore, some of the increased nuclear DHFR-mRNA was found to be in a non-polyadenylated form. Under conditions to examine only RNA synthesized during the drug exposure, FUra was found to markedly enhance the level of newly synthesized nuclear DHFR-mRNA in a dose-dependent manner, while also producing an apparent dose-dependent reduction in the cytoplasmic DHFR-mRNA. RNA fractionated by 1.5% agarose-urea gel electrophoresis revealed two major cytoplasmic DHFR-mRNA species approximately 1.8 and 0.8 kilobases in size. Following a 24-h FUra exposure, a dose-dependent loss of the 0.8-kilobase DHFR-mRNA was observed. The combined results of these experiments indicate that FUra treatment reduces the ability of nascent DHFR-mRNA to relocate to the cytoplasm, suggesting either an inhibition of mRNA processing or nuclear-cytoplasmic transport.
Armstrong
R D
RD
Lewis
M
M
Stern
S G
SG
Cadman
E C
EC
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D003562:Cytidine / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005472:Fluorouracil / Q000494:pharmacology*; D005786:Gene Expression Regulation; D007942:Leukemia, Experimental / Q000473:pathology; D051379:Mice; D012313:RNA / Q000032:analysis; D012333:RNA, Messenger / Q000378:metabolism*; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*; D014316:Tritium
D012333:RNA, Messenger; D014316:Tritium; D003562:Cytidine; D012313:RNA; D013762:Tetrahydrofolate Dehydrogenase; D005472:Fluorouracil