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Stacie Meaux,1 Ambro van Hoof,1,3, and Kristian E. Baker2,3,
1 Department of Microbiology and Molecular Genetics, University of Texas Health Science Center-Houston, Houston, TX 77030, USA
2 Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, OH 44106, USA
Corresponding author
Ambro van Hoof
Corresponding author
Kristian E. Baker
Eukaryotic mRNAs harboring premature translation termination codons are recognized and rapidly degraded by the nonsense-mediated mRNA decay (NMD) pathway. The mechanism for discriminating between mRNAs that terminate translation prematurely and those subject to termination at natural stop codons remains unclear. Studies in multiple organisms indicate that proximity of the termination codon to the 3′ poly(A) tail and the poly(A) RNA-binding protein, PAB1, constitute the critical determinant in NMD substrate recognition. We demonstrate that mRNA in yeast lacking a poly(A) tail can be destabilized by introduction of a premature termination codon and, importantly, that this mRNA is a substrate of the NMD machinery. We further show that, in cells lacking Pab1p, mRNA substrate recognition and destabilization by NMD are intact. These results establish that neither the poly(A) tail nor PAB1 is required in yeast for discrimination of nonsense codon-containing mRNA from normal by NMD.
名词解释：
1.无义介导的mRNA降解(nonsense-mediated mRNA decay,NMD)
无义介导的mRNA降解能够选择性降解含有翻译提前终止密码子(premature translation termination condon,PTC)的mRNA，从而防止对机体有害的截短蛋白
(truncated proteins)的产生，它是真核生物中广泛存在的一种高度保守的有效的监督机制。NMD与肿瘤发生发展过程中的基因突变有密切关系。
2.囊性纤维性变
囊性纤维性变(cystic fibrosis)以前也称为粘滞病或粘液粘稠病(mucoviscidosis)，（稠是说液体中含有某种成分很多的固体，跟 ‘稀’有相对意义）是一种严重隐性基因(autosomal recessive)遗传病。这遗传病的父母都带有隐性致病基因(recessive gene)，不过，他们表面上都是正常无恙。可是母亲每次怀孕时，胎儿就有25%的机会从父母双方各自获得致病基因以致患上遗传病。而胎儿有50%的机会，一如父母一样，带有隐性致病基因。胎儿只有25%的机会完全正常。
囊性纤维性变早在1936年首次在医学文献报道，它的特征是全身的外分泌腺（不是内分泌腺）的功能出了问题，牵连到身体很多器官都有毛病，尤其是肺部和消化道为甚。囊性纤维性变是在欧美最常见及死亡最多的遗传病。
附：
西储大学 Case Western Reserve University
设于俄亥俄州 Ohio的西储大学 Case Western Reserve University,CWRU 是该州最为知名的学府，评价良好，全校约有近10000名的学生，光是来自世界各地的学生就占学生总人数约3%左右，其它则来自美国各地的学生, 西储大学Case Western Reserve University,CWRU创校至今拥有不少的诺贝尔奖得主，因此西储大学Case Western Reserve University,CWRU的学术研究实力不容小歔.
西储大学Case Western Reserve University,CWRU 位于美国的俄亥俄州 Ohio、克里夫兰市 Cleveland，这里有个名为大学区University Circle的地方，校园面积 128 英亩。 克里夫兰市 Cleveland的艺文活动也不少，如：克利夫兰艺术博物馆、克利夫兰交响乐团、克利夫兰自然博物馆等的欣赏，都可以让人感染许多艺文气息另外亦有相当多的名胜古迹可供游览，或者也可以看场电影及观赏职业球赛等 在放假时可以自行开车到邻近的城市或是观光景点游玩。
Kristian E. Baker, Ph.D.
Instructor
Center for RNA Molecular Biology
Ph.D.: Genetics & Molecular Biology University of British Columbia, Vancouver, Canada 2002
Postdoc: Howard Hughes Medical Institute, University of Arizona, 2002-2005
Research: Mechanism of nonsense-mediated mRNA
decay in Saccharomyces cerevisiae.
mRNA harboring a premature termination codon is subject to rapid degradation by the nonsense-mediated mRNA decay (NMD) pathway. While the precise mechanism involved in discriminating NMD substrates from mRNA that is not targeted to NMD is unclear, the spatial relationship between the premature termination codon and additional features of the mRNA plays a critical role. My research focuses on determining how the various mRNA features contribute to NMD substrate recognition and how substrate recognition is translated into changes to the mRNA that result in repression of translation and susceptibility of the RNA to multiple pathways of degradation.
