TRANSLATION OF SINDBIS VIRUS MESSENGER-RNA - EFFECTS OF SEQUENCES DOWNSTREAM OF THE INITIATING CODON
TRANSLATION OF SINDBIS VIRUS MESSENGER-RNA - EFFECTS OF SEQUENCES DOWNSTREAM OF THE INITIATING CODON
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DOI：
10.1128/jvi.68.12.8111-8117.1994
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发表时间：
1994-12-01
影响因子：
5.4
通讯作者：
SCHLESINGER, S
中科院分区：
文献类型：
--
作者：
FROLOV, I;SCHLESINGER, S
将甲病毒辛德毕斯病毒开发为表达异源蛋白的载体的一个诱因是在感染细胞中积累的病毒结构蛋白水平非常高。尽管用异源基因替换结构蛋白基因应该会导致异源蛋白的同等积累，但辛德毕斯病毒衣壳蛋白的产生量比任何外源蛋白高10到20倍。包含与lacZ基因融合的辛德毕斯病毒26S mRNA的前275个核苷酸的嵌合mRNA也以较高水平进行翻译。位于起始衣壳蛋白翻译的AUG密码子下游的增强序列具有预测的发夹样结构；该区域的缺失会破坏其活性。这些序列在感染细胞中增强翻译，但在未感染细胞中具有相反的效果。此外，在感染细胞中这种RNA的翻译会被缺乏发夹样结构的第二种病毒RNA抑制，但后者RNA的翻译不受影响。我们提出发夹样结构在mRNA翻译过程中对核糖体的移动构成障碍。在感染细胞中，在这种mRNA基本上是唯一被翻译的RNA的条件下，核糖体移动的减缓给低浓度存在的因子一个结合到翻译复合物的机会，并允许形成高水平的功能性复合物。在未感染细胞以及翻译两种不同病毒亚基因组mRNA的感染细胞中，核糖体沿RNA移动的暂停不再是一个优势，因为所需的因子现在被其他翻译复合物占用。
One incentive for developing the alphavirus Sindbis virus as a vector for the expression of heterologous proteins is the very high level of viral structural proteins that accumulates in infected cells. Although replacement of the structural protein genes by a heterologous gene should lead to an equivalent accumulation of the heterologous protein, the Sindbis virus capsid protein is produced at a level 10- to 20-fold higher than that of any foreign protein. Chimeric mRNAs which contain the first 275 nucleotides of the Sindbis virus 26S mRNA fused to the lacZ gene are also translated at the higher level. The enhancing sequences, located downstream of the AUG codon that initiates translation of the capsid protein, have a predicted hairpin-like structure; deletions in this region destroy the activity. These sequences enhance translation in infected cells but have the opposite effect in uninfected cells. Furthermore, translation of this RNA in infected cells is suppressed by a second viral RNA lacking the hairpin-like structure, but translation of the latter RNA is not affected. We propose that the hairpin-like structure presents a barrier to the movement of the ribosomes during translation of mRNA. In infected cells, under conditions in which this mRNA is essentially the only RNA being translated, a slowdown in the transit of the ribosomes gives factors present at low concentrations a chance to bind to the translation complex and permits a high level of functional complexes to be formed. In uninfected cells and in infected cells translating two different viral subgenomic mRNAs, a pause in the movement of the ribosomes along the RNA is no longer an advantage, because the required factors are now usurped by other translation complexes.