A faux 3′-UTR promotes aberrant termination and triggers nonsense-mediated mRNA decay
A faux 3′-UTR promotes aberrant termination and triggers nonsense-mediated mRNA decay
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DOI：
10.1038/nature03060
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发表时间：
2004-11-04
期刊：
影响因子：
64.8
通讯作者：
Jacobson, A
中科院分区：
文献类型：
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作者：
Amrani, N;Ganesan, R;Jacobson, A
无义介导的信使RNA衰变（NMD）是由提前翻译终止（1-3）触发的，但区分提前终止和正常终止的特征尚不清楚。NMD的一个模型表明，在早期加工事件中与mRNA结合的衰变诱导因子通常通过延长核糖体而被去除，但当终止过早时仍与mRNA结合，从而引发快速周转（4）。最近的实验（5-7）挑战了这一观点，并提出了一个模型，该模型假定mRNA衰变是由过早终止的内在异常性质激活的（8，9）。在这里，我们使用引物延伸抑制（脚趾印）测定（10）来描绘核糖体定位，并发现酵母提取物中的过早翻译终止确实是异常的。在CAN 1 mRNA中遇到未成熟UAA或UGA密码子的核糖体不能释放，而是迁移到上游AUG。这种异常依赖于先前的无义密码子识别，并且在来自缺乏主要NMD因子Upf 1 p的细胞的提取物中被消除，或者通过用正常的3' -非翻译区（UTR）侧翼无义密码子来消除。Tethered poly（A）-binding protein（Pab 1 p）是一种类似于正常3 '-UTR的蛋白质，它募集终止因子Sup 35 p（eRF 3）并稳定含有无义的mRNA。这些发现表明有效的终止和mRNA稳定性依赖于正确配置的3 '-UTR。
Nonsense-mediated messenger RNA decay (NMD) is triggered by premature translation termination(1-3), but the features distinguishing premature from normal termination are unknown. One model for NMD suggests that decay-inducing factors bound to mRNAs during early processing events are routinely removed by elongating ribosomes but remain associated with mRNAs when termination is premature, triggering rapid turnover(4). Recent experiments(5-7) challenge this notion and suggest a model that posits that mRNA decay is activated by the intrinsically aberrant nature of premature termination(8,9). Here we use a primer extension inhibition ( toeprinting) assay(10) to delineate ribosome positioning and find that premature translation termination in yeast extracts is indeed aberrant. Ribosomes encountering premature UAA or UGA codons in the CAN1 mRNA fail to release and, instead, migrate to upstream AUGs. This anomaly depends on prior nonsense codon recognition and is eliminated in extracts derived from cells lacking the principal NMD factor, Upf1p, or by flanking the nonsense codon with a normal 3' - untranslated region (UTR). Tethered poly(A)-binding protein (Pab1p), used as a mimic of a normal 3'-UTR, recruits the termination factor Sup35p (eRF3) and stabilizes nonsense-containing mRNAs. These findings indicate that efficient termination and mRNA stability are dependent on a properly configured 3'-UTR.