Rosenberg J M, Sato P H
Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824.
Mol Pharmacol. 1993 Mar;43(3):491-7.
We previously reported that mRNA loses the ability to direct in vitro peptide synthesis after incubation with cisplatin. The present study was designed to determine the step in translation that is affected. The rates of translation reactions inhibited by cisplatin were biphasic, having an initial rate comparable to that of the uninhibited reaction before decreasing. Analysis of cisplatin-inhibited reactions in sucrose density gradients showed a decrease in polyribosome formation. These results are consistent with an inhibition of the initiation step of protein synthesis. Individual steps in initiation were tested by analyzing the formation of ribosomal subunits in sucrose gradients that resolve the incomplete complexes. Cisplatin caused an accumulation of 48 S particles accompanied by a decreased amount of completed 80 S initiation complexes. Similar results were obtained in experiments utilizing radiolabeled methionine or mRNA. We conclude that cisplatin blocks the initiation of translation by preventing the joining of the 60 S ribosomal subunit to the 48 S preinitiation subunit.
我们之前报道过，mRNA与顺铂孵育后失去了指导体外肽合成的能力。本研究旨在确定翻译过程中受影响的步骤。顺铂抑制的翻译反应速率呈双相性，在降低之前，其初始速率与未受抑制的反应相当。在蔗糖密度梯度中对顺铂抑制的反应进行分析，结果显示多核糖体形成减少。这些结果与蛋白质合成起始步骤受到抑制一致。通过分析蔗糖梯度中核糖体亚基的形成来测试起始过程中的各个步骤，该蔗糖梯度可分辨不完全复合物。顺铂导致48 S颗粒积累，同时完整的80 S起始复合物数量减少。在使用放射性标记甲硫氨酸或mRNA的实验中也获得了类似结果。我们得出结论，顺铂通过阻止60 S核糖体亚基与48 S起始前亚基的结合来阻断翻译起始。
