A single amino acid substitution in yeast eIF‐5A results in mRNA stabilization
A single amino acid substitution in yeast eIF‐5A results in mRNA stabilization
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DOI：
10.1093/emboj/17.10.2914
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发表时间：
1998-05
期刊：
影响因子：
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通讯作者：
D. Zuk;A. Jacobson
中科院分区：
文献类型：
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作者：
D. Zuk;A. Jacobson
大多数已知在mRNA周转中起作用的因子对于细胞活力不是必需的。为了确定关键因素，对10000种温度敏感的酵母菌株进行了筛选，以确定不稳定的CYH 2前mRNA水平的增加。在非允许温度下，5个突变体表现出CYH 2前mRNA和mRNA以及STE 2、URA 5和PAB 1 mRNA的衰减速率降低。其中，突变体ts 1159具有最广泛的表型。TIF 51 A基因（编码eIF-5A）的表达补充了ts 1159的温度敏感性生长和mRNA衰变表型。tif 51 A等位基因从这些细胞中被拯救出来，并显示在蛋白质的预测α螺旋片段内编码丝氨酸至脯氨酸的变化。TS 1159在限制性温度下也表现出蛋白质合成减少约30%。在与增加量的放线菌酮孵育的野生型细胞中测量氨基酸掺入表明，这种幅度的蛋白质合成减少不能解释在ts 1159中观察到的mRNA衰变缺陷的全部程度。有趣的是，ts 1159细胞在非允许温度下积累了未加帽的mRNA。这些结果表明，eIF-5A在mRNA周转中起作用，可能在去帽的下游起作用。
Most factors known to function in mRNA turnover are not essential for cell viability. To identify essential factors, ∼4000 temperature‐sensitive yeast strains were screened for an increase in the level of the unstable CYH2 pre‐mRNA. At the non‐permissive temperature, five mutants exhibited decreased decay rates of the CYH2 pre‐mRNA and mRNA, and the STE2, URA5 and PAB1 mRNAs. Of these, the mutant ts1159 had the most extensive phenotype. Expression of the TIF51A gene (encoding eIF‐5A) complemented the temperature‐sensitive growth and mRNA decay phenotypes of ts1159. The tif51A allele was rescued from these cells and shown to encode a serine to proline change within a predicted α‐helical segment of the protein. ts1159 also exhibited an ∼30% decrease in protein synthesis at the restrictive temperature. Measurement of amino acid incorporation in wild‐type cells incubated with increasing amounts of cycloheximide demonstrated that a decrease in protein synthesis of this magnitude could not account for the full extent of the mRNA decay defects observed in ts1159. Interestingly, the ts1159 cells accumulated uncapped mRNAs at the non‐permissive temperature. These results suggest that eIF‐5A plays a role in mRNA turnover, perhaps acting downstream of decapping.