Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0220723 (PCA)
 4,687 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Potassium iodide (KI) has been shown to impair thyroid protein biosynthesis both in vivo and in vitro. The present study was performed in order to clarify its mechanism of action. Ribonucleic acid (RNA) synthesis was studied in beef thyroid slices with either [32P] or [3H]-uridine as labelled precursors. Both KI and thyroxine (T4) at 10(-5) M significantly decreased RNA labelling under our conditions. In other experiments RNA degradation was examined in pulse-labelled and actinomycin D-treated slices. KI did not modify the degradation of the [3H]-RNA thus indicating that it interferes with the biosynthesis rather than with the degradation of RNA. Taking the perchloric acid soluble radioactivity as a rough index of the precursor pool the present results would indicate an action at this level. Both KC1O4 and methylmercapto-imidazole relieved the gland from the inhibitory action of KI, supporting the view that an intracellular and organified form of iodine is responsible for this action. Since T4 also reproduced the effects of KI on RNA synthesis we would like to propose iodothyronines as the intermediates of this action. Cyclic AMP has been shown to stimulate thyroid protein biosynthesis. The present results demonstrate an action at the RNA level. Cyclic AMP increased both the PCA-soluble and RNA-linked radioactivity, thus suggesting an effect at the RNA precursor pool. KI at 10(-5) M blocked the action of 2 mM cyclic AMP.
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PMID:Action of KI, thyroxine and cyclic AMP on [3H]uridine incorporation into the RNA of thyroid slices. 18 34

Thyrotrophin (TSH) regulates the biosynthesis of thyroid protein and RNA. This action is mediated by adenylate cyclase and cycl AMP. In the present study the action of cyclic GMP and cyclic CMP was investigated in beef slices. Both cyclic AMP and cyclic GMP significantly increased the incorporation of [3H]uridine into RNA. These effects were blocked by actinomycin D, suggesting that their action is located at a preor at a transcriptional step. The PCA soluble fraction radioactivity followed in parallel with tha variations observed in the RNA fraction, supporting the view that cyclic nucleotides may regulate RNA by modulating the nucleotide precursors pool. Cyclic CMP in concentrations between 0.35 to 1.5 mM progressively decreased the RNA labelling, and the values of the PCA soluble radioactivity again followed those of RNA. Furthermore, cyclic CMP also blocked the in vitro stimulatory action of cyclic AMP on the incorporation of [3H]leucine into protein, and of [3H]uridine into RNA. The present results provide the first information on the action of cyclic AMP on RNA synthesis and suggest that negative signals may also play a part in the regulation of thyroid function.
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PMID:Action of cyclic nucleotides on protein and RNA synthesis in the thyroid. 18 48

A fraction containing acid-soluble materials (PCA-extract) from Xenopus early blastulae preferentially inhibits the incorporation of [3H]uridine into 18S and 28S rRNA in Xenopus neurula cells. Pulse- laneling experiments revealed that whereas tubercidin, a known inhibitor of rRNA processing, produced a marked accumulation of the label in 40S pre-rRNA, Xenopus inhibitor suppressed labeling of the pre-rRNA. When tubercidin was added to cells whose activity for rRNA synthesis had been lowered by the Xenopus inhibitor, there was still an accumulation of label in the pre-rRNA. These results indicate that Xenopus inhibitor suppresses the synthesis of rRNA at transcription rather than at processing.
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PMID:Inhibitor of ribosomal RNA synthesis in Xenopus laevis embryos. VII. Inhibition of 40s pre-rRNA synthesis in Xenopus neurula cells. 672 9