SMG1 phosphorylates UPF1 (enhanced by Exon Junction Complex)

Stable Identifier
Reaction [transition]
Homo sapiens
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SMG1 phosphorylates UPF1 in vitro and in vivo (Denning et al. 2001, Yamashita et al. 2001, Kashima et al. 2006). Serines 1073, 1078, 1096, and 1116 in isoform 2 (Serines 1084, 1089, 1107, 1127 in isoform 1) are phosphorylated in vitro and phosphorylation at serines 1078 and 1096 has been confirmed in vivo (Yamashita et al. 2001, Ohnishi et al. 2003, Kashima et al. 2006). UPF1 also contains additional serine and threonine residues that could be phosphorylated. SMG8 and SMG9 associate with SMG1 and regulate the kinase activity of SMG1 (Yamashita et al. 2009). The phosphorylation reaction is rate-limiting in nonsense-mediated decay and is therefore regarded as a licensing step (reviewed in Rebbapragada and Lykke-Andersen 2009). Phosphorylation is enhanced by the exon junction complex, which can interact with UPF1 via UPF2 and/or UPF3 (Kashima et al. 2006, Ivanov et al. 2008) or via Y14:Magoh (Ivanov et al. 2008). SMG8 and SMG9 bind SMG1 and regulate its kinase activity (Yamashita et al. 2009, Fernandez et al. 2011).

Literature References
PubMed ID Title Journal Year
19417104 SMG-8 and SMG-9, two novel subunits of the SMG-1 complex, regulate remodeling of the mRNA surveillance complex during nonsense-mediated mRNA decay

Ohno, S, Katsuhata, Y, Yamashita, A, Ohnishi, T, Iwamatsu, A, Anderson, P, Izumi, N, Kurata, R, Hirano, H, Muramatsu, R, Morita, T, Saari, B, Hachiya, T, Kashima, I

Genes Dev 2009
11331269 Cloning of a novel phosphatidylinositol kinase-related kinase: characterization of the human SMG-1 RNA surveillance protein

Jamieson, L, Thompson, EA, Maquat, LE, Denning, G, Fields, AP

J Biol Chem 2001
14636577 Phosphorylation of hUPF1 induces formation of mRNA surveillance complexes containing hSMG-5 and hSMG-7

Ohno, S, Grimson, A, Yamashita, A, Ohnishi, T, Anderson, P, Hachiya, T, Anders, KR, Hentze, MW, Schell, T, Kashima, I

Mol Cell 2003
11544179 Human SMG-1, a novel phosphatidylinositol 3-kinase-related protein kinase, associates with components of the mRNA surveillance complex and is involved in the regulation of nonsense-mediated mRNA decay

Ohno, S, Taya, Y, Yamashita, A, Ohnishi, T, Kashima, I

Genes Dev 2001
20817927 Characterization of SMG-9, an essential component of the nonsense-mediated mRNA decay SMG1C complex

Bartolomé, RA, Ohno, S, Bamba, Y, Llorca, O, Yamashita, A, Teixidó, J, Arias-Palomo, E, Fernández, IS, Canales, MA

Nucleic Acids Res 2011
16452507 Binding of a novel SMG-1-Upf1-eRF1-eRF3 complex (SURF) to the exon junction complex triggers Upf1 phosphorylation and nonsense-mediated mRNA decay

Kataoka, N, Dreyfuss, G, Ohno, S, Hoshino, S, Morishita, R, Yamashita, A, Ohno, M, Izumi, N, Kashima, I

Genes Dev 2006
19359157 Execution of nonsense-mediated mRNA decay: what defines a substrate?

Rebbapragada, I, Lykke-Andersen, J

Curr Opin Cell Biol 2009
Catalyst Activity

protein kinase C activity of SMG1:UPF1:EJC:Translated mRNP [cytosol]

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