Shu Ping, Dai Huacheng, Gao Wenwu, Goldman Emanuel
Department of Microbiology & Molecular Genetics, New Jersey Medical School, University of Medicine & Dentistry of New Jersey, Newark, NJ 07103, USA.
Gene Expr. 2006;13(2):97-106. doi: 10.3727/000000006783991881.
Consecutive homologous codons that are rarely used in E. coli are known to inhibit translation to varying degrees. As few as two consecutive rare arginine codons exhibit a profound inhibition of translation when they are located in the 5' portion of a gene in E. coli. We have previously shown that nine consecutive rare CUA leucine codons cause almost complete inhibition of translation when they are placed after the 13th codon of a test message (although they do not inhibit translation when they are placed in the middle of the message). In the present work, we report that five consecutive rare CUA leucine codons exhibit approximately a threefold inhibition of translation when they are similarly placed after the 13th codon of a test message, compared to five consecutive common CUG leucine codons, in a T7 RNA polymerase-driven system. Further, by removing RNase III processing sites at the 3' ends of the mRNAs, we have manipulated the stability of the mRNAs encoding the test and control messages to see if decreasing mRNA stability might have an effect on the extent of translation inhibition by the rare leucine codons. However, the inhibition with the less stable mRNAs was similar to that with the stable mRNAs, approximately 3.4-fold, indicating that mRNA stability per se does not have a major influence on the effects of rare codons in this system.
已知在大肠杆菌中很少使用的连续同源密码子会在不同程度上抑制翻译。在大肠杆菌中，当基因的5'端存在仅两个连续的稀有精氨酸密码子时，就会对翻译产生显著抑制。我们之前已经表明，九个连续的稀有CUA亮氨酸密码子在置于测试信息的第13个密码子之后时，几乎会完全抑制翻译（尽管它们置于信息中间时不会抑制翻译）。在本研究中，我们报告称，在T7 RNA聚合酶驱动的系统中，与五个连续的常见CUG亮氨酸密码子相比，五个连续的稀有CUA亮氨酸密码子在同样置于测试信息的第13个密码子之后时，会表现出约三倍的翻译抑制。此外，通过去除mRNA 3'端的RNase III加工位点，我们操控了编码测试和对照信息的mRNA的稳定性，以查看降低mRNA稳定性是否可能对稀有亮氨酸密码子的翻译抑制程度产生影响。然而，稳定性较低的mRNA的抑制情况与稳定性较高的mRNA相似，约为3.4倍，这表明mRNA稳定性本身对该系统中稀有密码子的影响没有重大影响。
