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首页> 外文期刊>Molecular and Cellular Biology >Identification of a competitive translation determinant in the 3' untranslated region of alfalfa mosaic virus coat protein mRNA.
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Identification of a competitive translation determinant in the 3' untranslated region of alfalfa mosaic virus coat protein mRNA.

机译：在苜蓿花叶病毒外壳蛋白mRNA 3'非翻译区中竞争翻译决定簇的鉴定。

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We report that the competitive translational activity of alfalfa mosaic virus coat protein mRNA (CP RNA), a nonadenylated mRNA, is determined in part by the 3' untranslated region (UTR). Competitive translation was characterized both in vitro, with cotranslation assays, and in vivo, with microinjected Xenopus laevis oocytes. In wheat germ extracts, coat protein synthesis was constant when a fixed amount of full-length CP RNA was cotranslated with increasing concentrations of competitor globin mRNA. However, translation of CP RNA lacking the 3' UTR decreased significantly under competitive conditions. RNA stabilities were equivalent. In X. laevis oocytes, which are translationally saturated and are an inherently competitive translational environment, full-length CP RNA assembled into large polysomes and coat protein synthesis was readily detectable. Alternatively, CP RNA lacking the 3' UTR sedimented as small polysomes, and little coat protein was detected. Again, RNA stabilities were equivalent. Site-directed mutagenesis was used to localize RNA sequences or structures required for competitive translation. Since the CP RNA 3' UTR has an unusually large number of AUG nucleotide triplets, two AUG-containing sites were altered in full-length RNA prior to oocyte injections. Nucleotide substitutions at the sequence GAUG, 20 nucleotides downstream of the coat protein termination codon, specifically reduced full-length CP RNA translation, while similar substitutions at the next AUG triplet had little effect on translation. The competitive influence of the 3' UTR could be explained by RNA-protein interactions that affect translation initiation or by ribosome reinitiation at downstream AUG codons, which would increase the number of ribosomes committed to coat protein synthesis.
机译：我们报告苜蓿花叶病毒外壳蛋白mRNA（CP RNA），非腺苷酸化mRNA的竞争性翻译活性部分取决于3'非翻译区（UTR）。竞争翻译的特点是在体外用共翻译测定法，在体内用显微注射的非洲爪蟾卵母细胞表征。在小麦胚芽提取物中，当固定量的全长CP RNA与竞争性球蛋白mRNA浓度的增加进行共翻译时，外壳蛋白的合成是恒定的。但是，在竞争条件下，缺少3'UTR的CP RNA的翻译显着下降。 RNA稳定性是等效的。在X.laevis卵母细胞中，其翻译饱和并且是固有的竞争性翻译环境，全长CP RNA组装成大的多核糖体和外壳蛋白合成很容易被检测到。或者，缺少3'UTR的CP RNA沉淀为小多核糖体，并且检测到很少的外壳蛋白。同样，RNA稳定性是等效的。定点诱变用于定位竞争性翻译所需的RNA序列或结构。由于CP RNA 3'UTR具有异常多的AUG核苷酸三联体，因此在卵母细胞注射之前，全长RNA中两个包含AUG的位点发生了改变。在外壳蛋白终止密码子下游20个核苷酸处的序列GAUG处进行核苷酸取代，特异性地减少了全长CP RNA的翻译，而在下一个AUG三联体处进行的相似取代对翻译的影响很小。 3'UTR的竞争影响可以通过影响翻译起始的RNA蛋白质相互作用或下游AUG密码子处的核糖体重新初始化来解释，这将增加致力于外壳蛋白合成的核糖体的数量。

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