Ellis T J, Wagner G F
Department of Physiology, Faculty of Medicine, University of Western Ontario, London, Canada.
J Biol Chem. 1995 Jan 27;270(4):1960-5.
Stanniocalcin (STC) is a Ca(2+)-regulating hormone produced by the corpuscles of Stannius in bony fish. Calcium has been shown to stimulate STC synthesis at multiple levels including the level of gene expression. The purpose of this study was to determine the effects of Ca2+ on STC mRNA stability. The half-life of STC mRNA was measured in primary cultured trout corpuscles of Stannius cells maintained in either normal (1.2 mM) or high (1.9 mM) levels of extracellular calcium and treated with the transcriptional inhibitor alpha-amanitin. In cells maintained in 1.2 mM Ca2+, STC mRNA levels decreased progressively over time with an estimated half-life of approximately 71 h. However, message levels remained unchanged for up to 4 days in cells maintained in 1.9 mM Ca2+, indicating that the transcript had been stabilized in response to Ca2+ stimulation. Blocking transcription prior to exposing cells to high Ca2+ did not alter the stabilizing effects of the cation, indicating that synthesis and processing of the mRNA transcript were not involved in message stabilization. Inhibiting protein synthesis with cycloheximide also had no influence on the stabilizing effects of high calcium. The experiments involving cycloheximide further suggested that the mechanism of mRNA stabilization involved protein-nucleic acid interactions in the cytoplasm, whereby the polysomal complex protected the mRNA from degradation. These data demonstrate that the stimulatory effect of Ca2+ on STC gene expression is due, in part, to mRNA stabilization.
鲽鱼降钙素（STC）是一种由硬骨鱼斯坦尼斯小体产生的钙调节激素。研究表明，钙可在多个水平上刺激STC的合成，包括基因表达水平。本研究的目的是确定Ca2+对STC mRNA稳定性的影响。在原代培养的鳟鱼斯坦尼斯细胞中测量STC mRNA的半衰期，这些细胞维持在正常（1.2 mM）或高（1.9 mM）水平的细胞外钙环境中，并用转录抑制剂α-鹅膏蕈碱处理。在维持在1.2 mM Ca2+的细胞中，STC mRNA水平随时间逐渐下降，估计半衰期约为71小时。然而，在维持在1.9 mM Ca2+的细胞中，mRNA水平在长达4天的时间内保持不变，这表明转录本在Ca2+刺激下得到了稳定。在将细胞暴露于高钙之前阻断转录，不会改变阳离子的稳定作用，这表明mRNA转录本的合成和加工与信息稳定无关。用环己酰亚胺抑制蛋白质合成也对高钙的稳定作用没有影响。涉及环己酰亚胺的实验进一步表明，mRNA稳定的机制涉及细胞质中的蛋白质-核酸相互作用，其中多核糖体复合物保护mRNA不被降解。这些数据表明，Ca2+对STC基因表达的刺激作用部分归因于mRNA的稳定。
