Unusual bipartite mode of interaction between the nonsense-mediated decay factors, UPF1 and UPF2
Unusual bipartite mode of interaction between the nonsense-mediated decay factors, UPF1 and UPF2
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DOI：
10.1038/emboj.2009.175
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发表时间：
2009-08-05
期刊：
影响因子：
11.4
通讯作者：
Cusack, Stephen
中科院分区：
文献类型：
--
作者：
Clerici, Marcello;Mourao, Andre;Cusack, Stephen
无义介导的衰变（NMD）是一种真核生物的质量控制机制，它降解携带过早终止密码子的mRNA。在哺乳动物细胞中，当UPF 2与下游外显子连接复合物上的UPF 3结合时，NMD被触发，UPF 1与停滞的核糖体结合。我们报告的C-末端区域的UPF 2和完整的UPF 1之间的相互作用的结构研究。通过EM和SAXS确认的晶体结构显示UPF 1 CH-结构域以固定构型对接到其解旋酶结构域上。UPF 2的C-末端区域是天然展开的，但通过分离的α-螺旋和β-发夹元件与UPF 1 CH-结构域结合。α-螺旋区的结合强度比β-发夹区弱6倍，而组合元件的结合强度是β-发夹区的80倍。细胞分析表明，NMD受到破坏β-发夹结合的突变的严重影响，但不受仅影响α-螺旋结合的突变的影响。我们建议，UPF 2结合UPF 1的二分模式带来的核糖体和EJC在紧密接近形成一个紧密的复合物后，最初的弱遇到任何元素。The EMBO Journal（2009）28，2293-2306. doi：10.1038/doj.2009.175; 2009年6月25日在线发布
Nonsense-mediated decay (NMD) is a eukaryotic quality control mechanism that degrades mRNAs carrying premature stop codons. In mammalian cells, NMD is triggered when UPF2 bound to UPF3 on a downstream exon junction complex interacts with UPF1 bound to a stalled ribosome. We report structural studies on the interaction between the C-terminal region of UPF2 and intact UPF1. Crystal structures, confirmed by EM and SAXS, show that the UPF1 CH-domain is docked onto its helicase domain in a fixed configuration. The C-terminal region of UPF2 is natively unfolded but binds through separated alpha-helical and beta-hairpin elements to the UPF1 CH-domain. The alpha-helical region binds sixfold more weakly than the beta-hairpin, whereas the combined elements bind 80-fold more tightly. Cellular assays show that NMD is severely affected by mutations disrupting the beta-hairpin binding, but not by those only affecting alpha-helix binding. We propose that the bipartite mode of UPF2 binding to UPF1 brings the ribosome and the EJC in close proximity by forming a tight complex after an initial weak encounter with either element. The EMBO Journal (2009) 28, 2293-2306. doi: 10.1038/emboj.2009.175; Published online 25 June 2009