Multiple elements required for translation of plastid atpB mRNA lacking the Shine-Dalgarno sequence
Multiple elements required for translation of plastid atpB mRNA lacking the Shine-Dalgarno sequence
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DOI：
10.1093/nar/gkh682
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发表时间：
2004-06-01
影响因子：
14.9
通讯作者：
Sugiura, M
中科院分区：
文献类型：
--
作者：
Hirose, T;Sugiura, M
原核生物和真核生物的翻译起始机制不同。原核mrna通常在其5'-未翻译区（5'-UTR）中含有一个Shine-Dalgarno （SD）序列，作为核糖体结合位点。叶绿体具有类似原核生物的翻译机制，许多叶绿体mrna具有类似sd的序列，但其位置是可变的。烟草叶绿体atpB mrna不含sd样序列，在5'-UTR（起始密码子为-20 ~ -1）上富含u。突变mrna的体外翻译实验显示，包含起始密码子、AUG密码子及其上下文的非结构化序列是翻译所必需的。紫外交联实验表明，一个50 kDa的蛋白（p50）与5'-UTR结合。在5'-UTR中插入一个额外的起始区（sd序列和AUG），但不是在下游，阻止了原位点的翻译；然而，仅插入一个AUG三联体没有观察到抑制作用。我们假设对于atpB mRNA的翻译起始，核糖体进入上游区域，滑至起始密码子，并与p50和其他组分形成起始复合物。
The mechanism of translational initiation differs between prokaryotes and eukaryotes. Prokaryotic mRNAs generally contain within their 5'-untranslated region (5'-UTR) a Shine-Dalgarno (SD) sequence that serves as a ribosome-binding site. Chloroplasts possess prokaryotic-like translation machinery, and many chloroplast mRNAs have an SD-like sequence, but its position is variable. Tobacco chloroplast atpB mRNAs contain no SD-like sequence and are U-rich in the 5'-UTR (-20 to -1 with respect to the start codon). In vitro translation assays with mutated mRNAs revealed that an unstructured sequence encompassing the start codon, the AUG codon and its context are required for translation. UV crosslinking experiments showed that a 50 kDa protein (p50) binds to the 5'-UTR. Insertion of an additional initiation region (SD-sequence and AUG) in the 5'-UTR, but not downstream, arrested translation from the authentic site; however, no inhibition was observed by inserting only an AUG triplet. We hypothesize for translational initiation of the atpB mRNA that the ribosome enters an upstream region, slides to the start codon and forms an initiation complex with p50 and other components.