Gong Z Y, Brandhorst B P
Biology Department, McGill University, Montreal, Quebec, Canada.
Mol Cell Biol. 1988 Aug;8(8):3518-25. doi: 10.1128/mcb.8.8.3518-3525.1988.
An increased level of unpolymerized tubulin caused by depolymerization of microtubules in sea urchin larvae resulted in a rapid loss of tubulin mRNA, which was prevented by nearly complete inhibition of protein synthesis. Results of an RNA run-on assay indicated that inhibition of protein synthesis does not alter tubulin gene transcription. Analysis of the decay of tubulin mRNA in embryos in which RNA synthesis was inhibited by actinomycin D indicated that inhibition of protein synthesis prevents the destabilization of tubulin mRNA. The effect was similar whether mRNA was maintained on polysomes in the presence of emetine or anisomycin or displaced from the polysomes in the presence of puromycin or pactamycin; thus, the stabilization of tubulin mRNA is not dependent on the state of the polysomes after inhibition of protein synthesis. Even after tubulin mRNA declined to a low level after depolymerization of microtubules, it could be rescued by treatment of embryos with inhibitors of protein synthesis. Tubulin mRNA could be induced to accumulate prematurely in gastrulae but not in plutei if protein synthesis was inhibited, an observation that is indicative of the importance of the autogenous regulation of tubulin mRNA stability during embryogenesis. Possible explanations for the role of protein synthesis in the control of mRNA stability are discussed.
海胆幼虫微管解聚导致未聚合微管蛋白水平升高，进而导致微管蛋白mRNA迅速丢失，而蛋白质合成近乎完全抑制可防止这种情况发生。RNA连续分析结果表明，蛋白质合成的抑制不会改变微管蛋白基因的转录。对放线菌素D抑制RNA合成的胚胎中微管蛋白mRNA衰变的分析表明，蛋白质合成的抑制可防止微管蛋白mRNA的不稳定。无论mRNA是在依米丁或茴香霉素存在下维持在多核糖体上，还是在嘌呤霉素或放线菌酮存在下从多核糖体上脱离，效果都是相似的；因此，微管蛋白mRNA的稳定并不依赖于蛋白质合成抑制后多核糖体的状态。即使在微管解聚后微管蛋白mRNA下降到低水平，用蛋白质合成抑制剂处理胚胎仍可使其恢复。如果抑制蛋白质合成，微管蛋白mRNA可在原肠胚中过早积累，但在长腕幼虫中则不会，这一观察结果表明在胚胎发育过程中微管蛋白mRNA稳定性的自体调节很重要。文中讨论了蛋白质合成在控制mRNA稳定性中的作用的可能解释。
