Kameji T, Pegg A E
J Biol Chem. 1987 Feb 25;262(6):2427-30.
The effect of spermidine and spermine on the translation of the mRNAs for ornithine decarboxylase and S-adenosylmethionine decarboxylase was studied using a reticulocyte lysate system and specific antisera to precipitate these proteins. It was found that the synthesis of these key enzymes in the biosynthesis of polyamines was much more strongly inhibited by the addition of polyamines than was either total protein synthesis or the synthesis of albumin. Translation of the mRNA for S-adenosylmethionine decarboxylase was maximal in a lysate which had been substantially freed from polyamines by gel filtration. Addition of 80 microM spermine had no significant effect on total protein synthesis and stimulated albumin synthesis but reduced the production of S-adenosylmethionine decarboxylase by 76%. Similarly, addition of 0.8 mM spermidine reduced the synthesis of S-adenosylmethionine decarboxylase by 82% while albumin and total protein synthesis were similar to that found in the gel-filtered lysate. Translation of ornithine decarboxylase mRNA was greater in the gel-filtered lysate than in the control lysate but synthesis of ornithine decarboxylase was stimulated slightly by low concentrations of polyamines and was maximal at 0.2 mM spermidine or 20 microM spermine. Higher concentrations were strongly inhibitory with a 70% reduction occurring at 0.8 mM spermidine or 150 microM spermine. Further experiments in which both polyamines were added together confirmed that the synthesis of ornithine and S-adenosylmethionine decarboxylases were much more sensitive to inhibition by polyamines than protein synthesis as a whole. These results indicate that an important part of the regulation of polyamine biosynthesis by polyamines is due to a direct inhibitory effect of the polyamines on the translation of mRNA for these biosynthetic enzymes.
利用网织红细胞裂解物系统和特异性抗血清沉淀这些蛋白质，研究了亚精胺和精胺对鸟氨酸脱羧酶和S-腺苷甲硫氨酸脱羧酶mRNA翻译的影响。结果发现，在多胺生物合成中，这些关键酶的合成受到多胺添加的抑制作用比总蛋白质合成或白蛋白合成要强得多。通过凝胶过滤基本去除多胺的裂解物中，S-腺苷甲硫氨酸脱羧酶mRNA的翻译量最大。添加80微摩尔精胺对总蛋白质合成无显著影响，且刺激了白蛋白合成，但使S-腺苷甲硫氨酸脱羧酶的产量降低了76%。同样，添加0.8毫摩尔亚精胺使S-腺苷甲硫氨酸脱羧酶的合成降低了82%，而白蛋白和总蛋白质合成与凝胶过滤裂解物中的情况相似。凝胶过滤裂解物中鸟氨酸脱羧酶mRNA的翻译量高于对照裂解物，但低浓度多胺对鸟氨酸脱羧酶的合成有轻微刺激作用，在0.2毫摩尔亚精胺或20微摩尔精胺时达到最大值。更高浓度则有强烈抑制作用，在0.8毫摩尔亚精胺或150微摩尔精胺时降低70%。同时添加两种多胺的进一步实验证实，鸟氨酸脱羧酶和S-腺苷甲硫氨酸脱羧酶的合成比整体蛋白质合成对多胺抑制更为敏感。这些结果表明，多胺对多胺生物合成的调控的一个重要部分是由于多胺对这些生物合成酶mRNA翻译的直接抑制作用。
