Buckingham R H, Sörensen P, Pagel F T, Hijazi K A, Mims B H, Brechemier-Baey D, Murgola E J
Institut de Biologie Physico-Chimique, Paris, France.
Biochim Biophys Acta. 1990 Aug 27;1050(1-3):259-62. doi: 10.1016/0167-4781(90)90177-4.
The base sequence around nonsense codons affects the efficiency of nonsense codon suppression. Published data, comparing different nonsense sites in a mRNA, implicate the two bases downstream of the nonsense codon as major determinants of suppression efficiency. However, the results we report here indicate that the nature of the contiguous upstream codon can also affect nonsense suppression, as can the third (wobble) base of the contiguous downstream codon. These conclusions are drawn from experiments in which the two Ser codons UCU233 and UCG235 in a nonsense mutant form (UGA234) of the trpA gene in Escherichia coli have been replaced with other Ser codons by site-directed mutagenesis. Suppression of these trpA mutants has been studied in the presence of a UGA nonsense suppressor derived from glyT. We speculate that the non-site-specific effects of the two adjacent downstream bases may be largely at the level of the termination process, whereas more site-specific or codon-specific effects may operate primarily on the activity of the suppressor tRNA.
无义密码子周围的碱基序列会影响无义密码子抑制的效率。已发表的数据比较了mRNA中不同的无义位点，表明无义密码子下游的两个碱基是抑制效率的主要决定因素。然而，我们在此报告的结果表明，相邻上游密码子的性质也会影响无义抑制，相邻下游密码子的第三个（摆动）碱基也会如此。这些结论来自于实验，在实验中，通过定点诱变将大肠杆菌trpA基因无义突变形式（UGA234）中的两个Ser密码子UCU233和UCG235替换为其他Ser密码子。在存在源自glyT的UGA无义抑制子的情况下，研究了这些trpA突变体的抑制情况。我们推测，相邻下游两个碱基的非位点特异性效应可能主要在终止过程水平上起作用，而更多的位点特异性或密码子特异性效应可能主要作用于抑制tRNA的活性。
