Zhang Y, Dolph P J, Schneider R J
Department of Biochemistry, New York University Medical Center, New York 10016.
J Biol Chem. 1989 Jun 25;264(18):10679-84.
RNA secondary structure analysis was performed to understand the translation function of the adenovirus tripartite leader, a 200-nucleotide 5' noncoding region found on all late viral mRNAs. The tripartite leader facilitates the translation of viral mRNAs at late but not early times after infection and eliminates the normal requirement for the eukaryotic initiation factor 4F or cap binding protein complex. Secondary structures were determined by probing 5' or 3' end-labeled tripartite leader RNAs under nondenaturing conditions with various single strand-specific nucleases, and the information was used to generate a potential model structure. The resulting structure is attractive since it may explain the unusual translation behavior conferred by the tripartite leader. We demonstrate that the first leader segment is predominantly single-stranded, a property consistent with the ability to enhance translation and provide independence from cap binding protein complex. In contrast, the remaining two leader segments form a moderately stable base-paired structure, except for a large hairpin loop. To confirm these findings, the secondary structure of the tripartite leader was also probed when it was attached to a large segment of a messenger RNA and was found to be very similar to that of the individual leader RNA. These findings suggest several possible mechanisms to account for the translation activity of the tripartite leader.
进行了RNA二级结构分析，以了解腺病毒三联体前导序列的翻译功能，该序列是在所有晚期病毒mRNA上发现的一个200个核苷酸的5'非编码区。三联体前导序列在感染后的晚期而非早期促进病毒mRNA的翻译，并消除了对真核起始因子4F或帽结合蛋白复合物的正常需求。通过在非变性条件下用各种单链特异性核酸酶探测5'或3'末端标记的三联体前导RNA来确定二级结构，并利用这些信息生成一个潜在的模型结构。所得结构很有吸引力，因为它可能解释了三联体前导序列赋予的异常翻译行为。我们证明，第一个前导片段主要是单链的，这一特性与增强翻译以及独立于帽结合蛋白复合物的能力相一致。相比之下，其余两个前导片段形成了一个中等稳定的碱基配对结构，但有一个大的发夹环除外。为了证实这些发现，当三联体前导序列连接到信使RNA的一个大片段上时，也对其二级结构进行了探测，发现与单个前导RNA的二级结构非常相似。这些发现提示了几种可能的机制来解释三联体前导序列的翻译活性。
