Mechanism of non-spliceosomal mRNA splicing in the unfolded protein response pathway
Mechanism of non-spliceosomal mRNA splicing in the unfolded protein response pathway
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DOI：
10.1093/emboj/18.11.3119
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发表时间：
1999-06-01
期刊：
影响因子：
11.4
通讯作者：
Walter, P
中科院分区：
文献类型：
--
作者：
Gonzalez, TN;Sidrauski, C;Walter, P
未折叠蛋白应答是一种细胞内信号传导途径，其响应于内质网（ER）腔中错误折叠蛋白的积累，上调ER驻留分子伴侣的转录。该途径中的关键步骤是编码正转录调节因子Hac 1 p的mRNA的非常规的、受调节的剪接。在酵母酿酒酵母中，双功能跨膜激酶/核糖核酸内切酶Ire 1 p在两个剪接点处切割Hac 1 mRNA，并且tRNA连接酶将两个外显子连接在一起。我们已经在一个有效的体外反应中重建了HAC 1 mRNA剪接，并表明，在许多方面，HAC 1 mRNA剪接的机制类似于前tRNA剪接。特别是，Ire 1 p内切核酸裂解留下2 '，3'-环状磷酸，切除的外显子通过碱基配对保持关联，并且通过tRNA连接酶的外显子连接遵循与pre-tRNA剪接相同的化学步骤。迄今为止，这种RNA加工机制对于信使RNA来说是前所未有的。与tRNA剪接的惊人相似性相反，Ire 1 p识别的剪接点的结构特征与tRNA内切酶识别的不同。我们表明，小茎环结构预测形成在两个剪接点的HAC 1 mRNA的Ire 1 p切割所需的和足够的。
The unfolded protein response is an intracellular signaling pathway that, in response to accumulation of misfolded proteins in the lumen of the endoplasmic reticulum (ER), upregulates transcription of ER resident chaperones. A key step in this pathway is the nonconventional, regulated splicing of the mRNA encoding the positive transcriptional regulator Hac1p, In the yeast Saccharomyces cerevisiae, the bifunctional transmembrane kinase/endoribonuclease Ire1p cleaves HAC1 mRNA at both splice junctions and tRNA ligase joins the two exons together. We have reconstituted HAC1 mRNA splicing in an efficient in vitro reaction and show that, in many ways, the mechanism of HAC1 mRNA splicing resembles that of pre-tRNA splicing. In particular, Ire1p endonucleolytic cleavage leaves 2',3'-cyclic phosphates, the excised exons remain associated by base pairing, and exon ligation by tRNA ligase follows the same chemical steps as for pre-tRNA splicing. To date, this mechanism of RNA processing is unprecedented for a messenger RNA. In contrast to the striking similarities to tRNA splicing, the structural features of the splice junctions recognized by Ire1p differ from those recognized by tRNA endonuclease. We show that small stem-loop structures predicted to form at both splice junctions of HAC1 mRNA are required and sufficient for Ire1p cleavage.