The wobble hypothesis revisited:: Uridine-5-oxyacetic acid is critical for reading of G-ending codons
The wobble hypothesis revisited:: Uridine-5-oxyacetic acid is critical for reading of G-ending codons
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DOI：
10.1261/rna.731007
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发表时间：
2007-12-01
期刊：
影响因子：
4.5
通讯作者：
Bjork, Glenn R.
中科院分区：
文献类型：
--
作者：
Nasvall, S. Joakim;Chen, Peng;Bjork, Glenn R.
根据克里克的摆动假说，在摆动位置(34位)带有尿苷的tRNA识别A-和G-密码子，但不识别U-或C-结尾的密码子。然而，在摆动位置的U几乎总是被修饰的，并且在这个位置含有修饰的核苷尿苷-5-氧乙酸(CMO(5)U34)的肠杆菌tRNA除了识别A-和G-结尾的密码子外，还能识别U-(但不能识别C-)结尾的密码子。我们已经构建了一组肠杆菌突变体，只剩下含有CMO(5)U的tRNA来阅读Pro、丙氨酸、Valine和苏氨酸家族密码子中的所有四个密码子。根据这些突变体的表型，我们推测含有CMO(5)U的Pro、Alanine和Valine tRNAs阅读了包括C-末端密码子在内的所有四个密码子，而相应的苏氨酸tRNA则不能。引入了导致tRNA CMO(5)U缺失的cmoB突变。体内A位选择性检测显示，CMO(5)U34的存在刺激了CCU和CCC(Pro)、GCU(ALA)和GUC(Val)密码子的阅读。出乎意料的是，cmo5U对于G-Ending Pro、Ala和Val密码子的高效解码至关重要。显然，G34与U在mRNA上配对，而反向配对(U34-G)需要U34的修饰。
According to Crick's wobble hypothesis, tRNAs with uridine at the wobble position (position 34) recognize A- and G-, but not U- or C-ending codons. However, U in the wobble position is almost always modified, and Salmonella enterica tRNAs containing the modified nucleoside uridine-5-oxyacetic acid (cmo(5)U34) at this position are predicted to recognize U- (but not C-) ending codons, in addition to A- and G-ending codons. We have constructed a set of S. enterica mutants with only the cmo(5)U-containing tRNA left to read all four codons in the proline, alanine, valine, and threonine family codon boxes. From the phenotypes of these mutants, we deduce that the proline, alanine, and valine tRNAs containing cmo(5)U read all four codons including the C-ending codons, while the corresponding threonine tRNA does not. A cmoB mutation, leading to cmo(5)U deficiency in tRNA, was introduced. Monitoring A-site selection rates in vivo revealed that the presence of cmo(5)U34 stimulated the reading of CCU and CCC (Pro), GCU (Ala), and GUC (Val) codons. Unexpectedly, cmo5U is critical for efficient decoding of G- ending Pro, Ala, and Val codons. Apparently, whereas G34 pairs with U in mRNA, the reverse pairing (U34-G) requires a modification of U34.