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SMG-2 Is a Phosphorylated Protein Required for mRNA Surveillance in Caenorhabditis elegansand Related to Upf1p of Yeast

Authors :
Page, Michelle F.
Carr, Brian
Anders, Kirk R.
Grimson, Andrew
Anderson, Philip
Source :
Molecular and Cellular Biology; September 1999, Vol. 19 Issue: 9 p5943-5951, 9p
Publication Year :
1999

Abstract

mRNAs that contain premature stop codons are selectively degraded in all eukaryotes tested, a phenomenon termed “nonsense-mediated mRNA decay” (NMD) or “mRNA surveillance.” NMD may function to eliminate aberrant mRNAs so that they are not translated, because such mRNAs might encode deleterious polypeptide fragments. In both yeasts and nematodes, NMD is a nonessential system. Mutations affecting three yeast UPFgenes or seven nematode smggenes eliminate NMD. We report here the molecular analysis of smg-2of Caenorhabditis elegans.smg-2is homologous to UPF1of yeast and to RENT1 (also called HUPF1), a human gene likely involved in NMD. The striking conservation of SMG-2, Upf1p, and RENT1/HUPF1 in both sequence and function suggests that NMD is an ancient system, predating the divergence of most eukaryotes. Despite similarities in the sequences of SMG-2 and Upf1p, expression of Upf1p in C. elegansdoes not rescue smg-2mutants. We have prepared anti-SMG-2 polyclonal antibodies and identified SMG-2 on Western blots. SMG-2 is phosphorylated, and mutations of the six other smggenes influence the state of SMG-2 phosphorylation. In smg-1,smg-3, and smg-4mutants, phosphorylation of SMG-2 was not detected. In smg-5, smg-6, and smg-7mutants, a phosphorylated isoform of SMG-2 accumulated to abnormally high levels. In smg-2(r866)and smg-2(r895)mutants, which harbor single amino acid substitutions of the SMG-2 nucleotide binding site, phosphorylated SMG-2 accumulated to abnormally high levels, similar to those observed in smg-5, smg-6, and smg-7mutants. We discuss these results with regard to the in vivo functions of SMG-2 and NMD.

Details

Language :
English
ISSN :
02707306 and 10985549
Volume :
19
Issue :
9
Database :
Supplemental Index
Journal :
Molecular and Cellular Biology
Publication Type :
Periodical
Accession number :
ejs62636843
Full Text :
https://doi.org/10.1128/MCB.19.9.5943