Cloning of a novel phosphatidylinositol kinase-related kinase. Characterization of the human SMG-1 RNA surveillance protein

Gabriela Denning, Lee Jamieson, Lynne E. Maquat, E Aubrey Thompson, Alan P Fields

Research output: Contribution to journalArticle

116 Citations (Scopus)

Abstract

We have cloned and characterized a new member of the phosphatidylinositol kinase (PIK)-related kinase family. This gene, which we term human SMG-1 (hSMG-1), is orthologous to Caenorhabditis elegans SMG-1, a protein that functions in nonsense-mediated mRNA decay (NMD). cDNA sequencing revealed that hSMG-1 encodes a protein of 3031 amino acids containing a conserved kinase domain, a C-terminal domain unique to the PIK-related kinases and an FKBP12-rapamycin binding-like domain similar to that found in the PIK-related kinase mTOR. Immunopurified FLAG-tagged hSMG-1 exhibits protein kinase activity as measured by autophosphorylation and phosphorylation of the generic PIK-related kinase substrate PHAS-1. hSMG-1 kinase activity is inhibited by high nanomolar concentrations of wortmannin (IC50 = 105 nM) but is not inhibited by a FKBP12-rapamycin complex. Mutation of conserved residues within the kinase domain of hSMG-1 abolishes both autophosphorylation and substrate phosphorylation, demonstrating that hSMG-1 exhibits intrinsic protein kinase activity. hSMG-1 phosphorylates purified hUpf1 protein, a phosphoprotein that plays a critical role in NMD, at sites that are also phosphorylated in whole cells. Based on these data, we conclude that hSMG-1 is the human orthologue to C. elegans SMG-1. Our data indicate that hSMG-1 may function in NMD by directly phosphorylating hUpf1 protein at physiologically relevant sites.

Original languageEnglish (US)
Pages (from-to)22709-22714
Number of pages6
JournalJournal of Biological Chemistry
Volume276
Issue number25
DOIs
StatePublished - Jun 22 2001
Externally publishedYes

Fingerprint

Cloning
Phosphatidylinositols
Organism Cloning
Phosphotransferases
RNA
Nonsense Mediated mRNA Decay
Proteins
Tacrolimus Binding Protein 1A
Caenorhabditis elegans
Phosphorylation
Sirolimus
Protein Kinases
Messenger RNA
Phosphoproteins
Substrates
Inhibitory Concentration 50
Complementary DNA
Genes
Amino Acids
Mutation

ASJC Scopus subject areas

  • Biochemistry

Cite this

Cloning of a novel phosphatidylinositol kinase-related kinase. Characterization of the human SMG-1 RNA surveillance protein. / Denning, Gabriela; Jamieson, Lee; Maquat, Lynne E.; Thompson, E Aubrey; Fields, Alan P.

In: Journal of Biological Chemistry, Vol. 276, No. 25, 22.06.2001, p. 22709-22714.

Research output: Contribution to journalArticle

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