The cryo-EM structure of the UPF-EJC complex shows UPF1 poised toward the RNA 3′ end
The cryo-EM structure of the UPF-EJC complex shows UPF1 poised toward the RNA 3′ end
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DOI：
10.1038/nsmb.2287
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发表时间：
2012-05-01
影响因子：
16.8
通讯作者：
Llorca, Oscar
中科院分区：
文献类型：
--
作者：
Melero, Roberto;Buchwald, Gretel;Llorca, Oscar
无义介导的mRNA衰变（NMD）是一种真核生物的监视途径，其降解含有提前终止密码子（PTC）的异常mRNA。国家导弹防御系统在联警察部队的监视综合设施在一个警察部队附近集结时启动。在人类中，UPF组装由外显子连接复合物（EJC）促进。我们研究了人UPF复合物的分子结构结合EJC冷冻EM和使用额外的EM，MS和生化相互作用数据的位置限制。七聚体组装是围绕UPF2构建的，UPF2是一种具有环状结构的支架蛋白，其围绕UPF1的CH结构域闭合，使解旋酶区域保持在可接近和解旋能力状态。UPF2还定位UPF3以与EJC相互作用。其几何形状使得该瞬时复合物使UPF1平衡以引发朝向mRNP的3'端的解旋酶活性。
Nonsense-mediated mRNA decay (NMD) is a eukaryotic surveillance pathway that degrades aberrant mRNAs containing premature termination codons (PTCs). NMD is triggered upon the assembly of the UPF surveillance complex near a PTC. In humans, UPF assembly is prompted by the exon junction complex (EJC). We investigated the molecular architecture of the human UPF complex bound to the EJC by cryo-EM and using positional restraints from additional EM, MS and biochemical interaction data. The heptameric assembly is built around UPF2, a scaffold protein with a ring structure that closes around the CH domain of UPF1, keeping the helicase region in an accessible and unwinding-competent state. UPF2 also positions UPF3 to interact with the EJC. The geometry is such that this transient complex poises UPF1 to elicit helicase activity toward the 3' end of the mRNP.