Cellular mRNAs access second ORFs using a novel amino acid sequence-dependent coupled translation termination-reinitiation mechanism.
Cellular mRNAs access second ORFs using a novel amino acid sequence-dependent coupled translation termination-reinitiation mechanism.
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DOI：
10.1261/rna.041574.113
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发表时间：
2014-03
期刊：
影响因子：
--
通讯作者：
Easton AJ
中科院分区：
文献类型：
--
作者：
Gould PS;Dyer NP;Croft W;Ott S;Easton AJ
多顺反子转录物在人类基因组中是罕见的，因为需要不寻常的机制来翻译下游ORF，包括泄漏扫描，IRES或耦合终止-再起始机制。在这里，作者设计了一种算法来识别人类转录组中具有两个重叠ORF的mRNA，其中耦合的终止-再起始机制可能相关。在鉴定的数千个这样的转录本中，24个中的22个被认为表达来自第二个ORF的蛋白质，这表明3′ UTR本身具有相当大的编码潜力。这些成绩单中的五个似乎依赖于终止-再起始机制，其中一个依赖于一个特定的富含谷氨酸的重复肽序列在羧基末端的ORF 1的耦合机制是有效的。多顺反子转录物在人类基因组中被认为是罕见的。真核基因的内部ORF翻译的起始已经显示使用泄漏扫描或高度结构化的IRES区域来访问起始密码子。对哺乳动物病毒的研究发现了一种偶联翻译终止-再起始的机制，该机制允许翻译额外的ORF。在这里，核糖体终止ORF-1的翻译易位上游重新启动ORF-2的翻译。我们已经设计了一种算法来识别人类转录组中的mRNA，其中主要ORF-1与能够编码长度至少为50个aa的产物的第二ORF重叠。这确定了代表2214个基因的4368个转录本。我们研究了24个转录本，其中22个被证明表达来自ORF-2的蛋白质，这突出表明3′ UTR比以前怀疑的更频繁地包含蛋白质编码潜力。5个转录本通过翻译终止-再起始的偶联过程进入ORF-2。对编码CASQ 2蛋白的一个转录本的分析表明，实现细胞mRNA偶联过程的机制是新颖的。这一过程不受mRNA序列的指导，但需要在终止ORF-1蛋白的羧基末端有一个富含组氨酸的重复区。天冬氨酸密码子的摆动突变的引入没有影响，而谷氨酸重复取代天冬氨酸消除翻译偶联。这是第一个描述的协调表达的两种蛋白质从细胞mRNA使用耦合翻译终止-再起始过程，是第一个例子，这样的过程中确定的氨基酸水平。
Polycistronic transcripts are rare in the human genome as unusual mechanisms are needed to translate the downstream ORFs, including leaky scanning, IRESs, or coupled termination–reinitiation mechanisms. Here the authors have devised an algorithm to identify mRNAs in the human transcriptome with two overlapping ORFs where a coupled termination–reinitiation mechanism might be relevant. Of the thousands of such transcripts identified, 22 of 24 were seen to express a protein from the second ORF suggesting that 3′ UTRs themselves have considerable coding potential. Five of these transcripts appeared to depend on a termination–reinitiation mechanism, and one of these depended on a specific aspartate-rich repeat peptide sequence at the carboxyl terminus of ORF1 for the coupling mechanism to be effective. Polycistronic transcripts are considered rare in the human genome. Initiation of translation of internal ORFs of eukaryotic genes has been shown to use either leaky scanning or highly structured IRES regions to access initiation codons. Studies on mammalian viruses identified a mechanism of coupled translation termination–reinitiation that allows translation of an additional ORF. Here, the ribosome terminating translation of ORF-1 translocates upstream to reinitiate translation of ORF-2. We have devised an algorithm to identify mRNAs in the human transcriptome in which the major ORF-1 overlaps a second ORF capable of encoding a product of at least 50 aa in length. This identified 4368 transcripts representing 2214 genes. We investigated 24 transcripts, 22 of which were shown to express a protein from ORF-2 highlighting that 3′ UTRs contain protein-coding potential more frequently than previously suspected. Five transcripts accessed ORF-2 using a process of coupled translation termination–reinitiation. Analysis of one transcript, encoding the CASQ2 protein, showed that the mechanism by which the coupling process of the cellular mRNAs was achieved was novel. This process was not directed by the mRNA sequence but required an aspartate-rich repeat region at the carboxyl terminus of the terminating ORF-1 protein. Introduction of wobble mutations for the aspartate codon had no effect, whereas replacing aspartate for glutamate repeats eliminated translational coupling. This is the first description of a coordinated expression of two proteins from cellular mRNAs using a coupled translation termination–reinitiation process and is the first example of such a process being determined at the amino acid level.
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DOI：
10.1083/jcb.108.2.229
发表时间：
1989-02
期刊：
The Journal of cell biology
影响因子：
--
作者：
Kozak M
通讯作者：
Kozak M
影响因子：
5.3
作者：
PEABODY, DS;BERG, P
通讯作者：
BERG, P
影响因子：
5.4
作者：
Gould, Phillip Spencer;Easton, Andrew John
通讯作者：
Easton, Andrew John
影响因子：
4.5
作者：
Powell, Michael L.;Napthine, Sawsan;Brown, T. David K.
通讯作者：
Brown, T. David K.
影响因子：
14.9
作者：
Sloan, J;Kinghorn, JR;Unkles, SE
通讯作者：
Unkles, SE