K. Hadjiolova, E. Golovinsky, A. Hadjiolov
Sep 7, 1973
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Influential Citations
16
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Journal
Biochimica et biophysica acta
Abstract
Abstract The action of 5-fluoroorotic acid on the in vivo [ 14 C]orotate labelling of mouse liver RNA was studied. The incorporation of 5-fluoroorotic acid into polynucleotide chains has the following effects: 1. 1. The labelling of nuclear and cytoplasmic 28-S and 18-S rRNA is almost completely inhibited, while the transcription of 45-S precursor rRNA and its early processing to 32-S and 21-S rRNA is not affected by the drug. Therefore, 5-fluoroorotic acid blocks selectively the last steps of rRNA maturation. The synthesis of nuclear 5-S rRNA is only slightly inhibited, but its transport to cytoplasmic ribosomes is blocked. 2. 2. The labelling of heterogeneous nuclear RNA and messenger-like RNA of cytoplasmic polysomes and free postmicrosomal ribonucleoproteins is not affected by 5-fluoroorotic acid. The drug causes the appearance of rapidly labelled degradation products in the cytoplasmic soluble RNA fraction, which indicates enhanced degradation of messenger-like RNA. 3. 3. Administration of 5-fluoroorotic acid does not inhibit either the synthesis of nuclear precursor tRNA, its conversion into mature nuclear tRNA or the appearance of free and ribosome-bound tRNA in the cytoplasm. It is suggested that the interference of 5-fluoroorotic with a definite step of rRNA maturation acid may be useful in the elucidation of the molecular mechanisms of this process and of the biological effects of the drug.