Jäck H M, Berg J, Wabl M
Laboratory of Radiobiology and Environmental Health, University of California, San Francisco 94143-0750.
Eur J Immunol. 1989 May;19(5):843-7. doi: 10.1002/eji.1830190510.
When termination codons were introduced into exons of the gene for Ig mu chain, steady-state levels of mu mRNA were reduced, both at the pre-B cell stage and at the plasma cell stage. A termination codon in the variable region gene segment and a termination codon in the second exon of the constant region gene segment had effects of similar magnitude. When the termination codon was deleted, the original level of mRNA was restored. The rate of mu gene transcription was the same whether or not a termination codon was present. Therefore, the termination codons must reduce the amount of the mRNA by reducing its stability. Since the introduced termination codons prematurely terminate translation and, in so doing, change the ribosome load on the mRNA, we conclude that mu mRNA stability is conferred in part by ribosomal protection from enzymatic degradation. We propose that the differences in mu mRNA stability during B lymphocyte differentiation are due to different amounts of ribosomes available for translation.
当终止密码子被引入免疫球蛋白μ链基因的外显子时，在pre - B细胞阶段和浆细胞阶段，μ mRNA的稳态水平均降低。可变区基因片段中的终止密码子和恒定区基因片段第二个外显子中的终止密码子具有相似程度的影响。当终止密码子被删除时，mRNA恢复到原始水平。无论是否存在终止密码子，μ基因的转录速率都是相同的。因此，终止密码子必定是通过降低mRNA的稳定性来减少其数量。由于引入的终止密码子会过早终止翻译，从而改变mRNA上的核糖体负载，我们得出结论，μ mRNA的稳定性部分是由核糖体对酶促降解的保护作用赋予的。我们提出，B淋巴细胞分化过程中μ mRNA稳定性的差异是由于可用于翻译的核糖体数量不同所致。
