Phosphorylation of hUPF1 induces formation of mRNA surveillance complexes containing hSMG-5 and hSMG-7
Phosphorylation of hUPF1 induces formation of mRNA surveillance complexes containing hSMG-5 and hSMG-7
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DOI：
10.1016/s1097-2765(03)00443-x
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发表时间：
2003-11-01
期刊：
影响因子：
16
通讯作者：
Ohno, S
中科院分区：
文献类型：
--
作者：
Ohnishi, T;Yamashita, A;Ohno, S
真核细胞中含有提前终止密码子(PTCs)的mRNAs通过一种被称为无义介导的mRNA衰变(NMD)的过程来降解。有人建议NMD要求含有UPF1/SMG-2的mRNA监测复合体识别PTC。在多细胞生物中，UPF1/SMG-2是一种磷酸化蛋白，其磷酸化参与了NMD的发生。在这里，我们证明了磷酸化的hUPF1，人类UPF1/SMG-2的同源基因，与线虫NMD蛋白SMG-5和SMG-7的人类同源基因形成了复合体。该复合体还与蛋白磷酸酶2A(PP2A)结合，导致hUPF1的去磷酸化。与P-hUPF1保持相互作用但不能诱导其去磷酸化的HSMG-5突变体的过表达会损害NMD，提示NIVID需要P-hUPF1去磷酸化。我们还发现，P-hUPF1形成了不同的络合物，包含不同的hUPF3A异构体。我们认为，HSMG-1和PP2A分别对hUPF1的顺序磷酸化和去磷酸化有助于mRNA监视复合体的重构。
Eukaryotic mRNAs containing premature termination codons (PTCs) are degraded by a process known as nonsense-mediated mRNA decay (NMD). NMD has been suggested to require the recognition of PTC by an mRNA surveillance complex containing UPF1/SMG-2. In multicellular organisms, UPF1/SMG-2 is a phosphoprotein, and its phosphorylation contributes to NMD. Here we show that phosphorylated hUPF1, the human ortholog of UPF1/SMG-2, forms a complex with human orthologs of the C. elegans NMD proteins SMG-5 and SMG-7. The complex also associates with protein phosphatase 2A (PP2A), resulting in dephosphorylation of hUPF1. Overexpression of hSMG-5 mutants that retain interaction with P-hUPF1 but which cannot induce its dephosphorylation impair NMD, suggesting that NIVID requires P-hUPF1 dephosphorylation. We also show that P-hUPF1 forms distinct complexes containing different isoforms of hUPF3A. We propose that sequential phosphorylation and dephosphorylation of hUPF1 by hSMG-1 and PP2A, respectively, contribute to the remodeling of the mRNA surveillance complex.