出芽酵母中RNA剪接依赖的无义介导的mRNA衰变的机理研究

项目名称： 出芽酵母中RNA剪接依赖的无义介导的mRNA衰变的机理研究

项目编号： No.31471234

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 遗传学与生物信息学、细胞生物学

项目作者： 文继开

作者单位： 华南农业大学

项目金额： 85万元

中文摘要： 无义介导的核糖核酸衰减（NMD）是一种存在于真核生物细胞内高度保守的核糖核酸降解现象。NMD由信使核糖核酸的编码区中存在的无义突变所引发，需要核糖体结合到核糖核酸且依赖翻译的进行。对NMD机理的阐释一直是一个研究热点，但是在酵母和人类细胞中的研究结果仍然存在一定的不同。在出芽酵母及其他低等生物中，该降解过程取决于无义突变与下游poly（A）尾的距离；而在人类细胞的研究中表明，位于无义突变下游的内含子所导致的核糖核酸剪接，对NMD的发生有决定性的影响。 我们在裂殖酵母的相关研究中，发现核糖核酸的剪接的确可以诱发NMD；但是RNA剪接对降解的增强效应无需在无义突变的下游发生。我们在出芽酵母中也有类似的发现，拟在出芽酵母中，进一步研究核糖核酸剪接与NMD之间的关系来揭示核糖核酸剪接对翻译的影响，寻找参与该过程的剪接因子，阐述RNA剪接依赖的NMD机理，表明RNA加工在基因表达调控中的重要作用。

中文关键词： 基因表达调控；信使核糖核酸；无义介导的核糖核酸衰减；翻译；剪接因子

英文摘要： Nonsense mediated mRNA decay (NMD) is a conserved mRNA degradation pathway in eukaryotes. NMD is induced by a nonsense mutation in mRNA coding region, requires ribosomes and couples to translation. Currently we still do not understand exactly how a ribosome differentiates a premature termination condon (PTC) from the normal/native stop codon. In S. cerevisiae, many studies revealed that poly(A) tail, the downstream proximal sequence of the stop codon, plays a pivot role, which is supported by recent studies from Drosophila melanogaster, C. elegans, and human cells. It was believed that cytoplasmic poly(A) binding protein (PABP), docking on poly(A) tail, helps ribosome to confirm if the stop codon is native or prematured. However, contrastly, many studies from human cells suggested that a downstream intron has a key function in efficient NMD, via an exon junction complex(EJC), which binds to mRNA after intron spliced, acting as a platform complex to recruit key NMD factors. In our previous study, it was observed that splicing did enhance NMD in fission yeast, S. pombe. The splicing enhancement does require an intron, but regardless of the location downstream or upstream of an PTC. More interestingly, the intron enhancement in S. pombe NMD is independent of the presence of EJC. The initial experiment in S. cerevisiae also suggested that the splicing does enhance NMD. We are going to investigate the mechanism of how the splicing functions in NMD in S. cerevisiae, and whether splicing affects the eukaryotic translation or not. Furthermore, by studying the relationship between splicing and translation, we are able to reveal the important function of RNA process in the regulation of gene expression.

英文关键词： regulation of gene expression;mRNA;nonsense-mediated mRNA decay;translation;splicing factor