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首页> 外文期刊>Molecular and Cellular Biology >Ski6p Is a Homolog of RNA-Processing Enzymes That Affects Translation of Non-Poly(A) mRNAs and 60S Ribosomal Subunit Biogenesis
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Ski6p Is a Homolog of RNA-Processing Enzymes That Affects Translation of Non-Poly(A) mRNAs and 60S Ribosomal Subunit Biogenesis

机译：Ski6p是影响非Poly（A）mRNA和60S核糖体亚基生物发生翻译的RNA加工酶的同源物。

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We mapped and cloned SKI6 of Saccharomyces cerevisiae, a gene that represses the copy number of the L-A double-stranded RNA virus, and found that it encodes an essential 246-residue protein with homology to a tRNA-processing enzyme, RNase PH. The ski6-2 mutant expressed electroporated non-poly(A) luciferase mRNAs 8- to 10-fold better than did the isogenic wild type. No effect of ski6-2 on expression of uncapped or normal mRNAs was found. Kinetics of luciferase synthesis and direct measurement of radiolabeled electroporated mRNA indicate that the primary effect of Ski6p was on efficiency of translation rather than on mRNA stability. Both ski6 and ski2 mutants show hypersensitivity to hygromycin, suggesting functional alteration of the translation apparatus. The ski6-2 mutant has normal amounts of 40S and 60S ribosomal subunits but accumulates a 38S particle containing 5′-truncated 25S rRNA but no 5.8S rRNA, apparently an incomplete or degraded 60S subunit. This suggests an abnormality in 60S subunit assembly. The ski6-2 mutation suppresses the poor expression of the poly(A)? viral mRNA in a strain deficient in the 60S ribosomal protein L4. Thus, a ski6mutation bypasses the requirement of the poly(A) tail for translation, allowing better translation of non-poly(A) mRNA, including the L-A virus mRNA which lacks poly(A). We speculate that the derepressed translation of non-poly(A) mRNAs is due to abnormal (but full-size) 60S subunits.
机译：我们绘制并克隆了酿酒酵母（Saccharomyces cerevisiae）的 SKI6 ，该基因可抑制LA双链RNA病毒的拷贝数，并发现它编码必需的246个残基蛋白。与tRNA加工酶RNase PH具有同源性。 ski6-2 突变体表达的电穿孔非poly（A）荧光素酶mRNA比同基因野生型好8到10倍。未发现 ski6-2 对未封端或正常mRNA表达的影响。荧光素酶合成动力学和放射性标记的电穿孔mRNA的直接测量表明，Ski6p的主要作用是翻译效率，而不是mRNA稳定性。 ski6 和 ski2 突变体均显示对潮霉素过敏，表明翻译装置的功能发生了变化。 ski6-2 突变体具有正常数量的40S和60S核糖体亚基，但会积聚38S颗粒，其中包含5'截短的25S rRNA但不包含5.8S rRNA，显然是不完整或降解的60S亚基。这表明60S亚基组装异常。在缺乏60S核糖体蛋白L4的菌株中， ski6-2 突变抑制了poly（A）β病毒mRNA的不良表达。因此， ski6 突变绕开了poly（A）尾部对翻译的要求，从而可以更好地翻译非poly（A）mRNA，包括缺少poly（A）的L-A病毒mRNA。我们推测非poly（A）mRNA的抑制翻译是由于异常（但全尺寸）60S亚基。

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