The Key Laboratory of Stem Cell Biology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and Shanghai Jiao Tong University School of Medicine, 225 South Chong Qing Road, Shanghai 200025, China.
Cell Res. 2010 Apr;20(4):445-57. doi: 10.1038/cr.2010.25. Epub 2010 Feb 16.
A single mammalian transcript normally encodes one protein, but the transcript of GNAS (G-protein alpha-subunit) contains two reading frames and produces two structurally unrelated proteins, XLalphas and ALEX. No other confirmed GNAS-like dual-coding transcripts have been reported to date, even though many such candidate genes have been predicted by bioinformatics analysis. In this study, we constructed a series of vectors to test how two protein products were translated from a single transcript in vitro. The length of the ORF (open reading frame), position of the first AUG and the Kozak motif were found to be important factors. These factors, as well as 55-bp NMD (nonsense-mediated mRNA decay) rule, were used in a bioinformatics search for candidate dual-coding transcripts. A total of 1307, 750 and 474 two-ORF-containing transcripts were found in human, mouse and rat, respectively, of which 170, 89 and 70, respectively, were found to be potential dual-coding transcripts. Most transcripts showed low conservation among species. Interestingly, dual-coding transcripts were significantly enriched for transcripts from the zinc-finger protein family, which are usually DNA-binding proteins involved in regulation of the transcription process.
一个哺乳动物的转录本通常编码一个蛋白质，但 GNAS（G 蛋白α亚基）的转录本包含两个读码框，并产生两种结构上不相关的蛋白质，XLalphas 和 ALEX。迄今为止，尚未有其他经证实的 GNAS 样双编码转录本被报道，尽管通过生物信息学分析预测了许多此类候选基因。在这项研究中，我们构建了一系列载体来测试一个转录本如何在体外翻译出两种蛋白质产物。ORF（开放阅读框）的长度、第一个 AUG 的位置和 Kozak 基序被发现是重要因素。这些因素以及 55-bp NMD（无意义介导的 mRNA 衰变）规则，被用于生物信息学搜索候选双编码转录本。在人类、小鼠和大鼠中，分别发现了全长为 1307、750 和 474 的两个 ORF 包含的转录本，其中分别有 170、89 和 70 个被认为是潜在的双编码转录本。大多数转录本在物种间的保守性较低。有趣的是，双编码转录本在锌指蛋白家族的转录本中显著富集，这些转录本通常是参与转录过程调控的 DNA 结合蛋白。
