SMG-5, required for C.elegans nonsense-mediated mRNA decay, associates with SMG-2 and protein phosphatase 2A.
mRNAs that contain premature stop codons are degraded selectively and rapidly in eukaryotes, a phenomenon termed 'nonsense-mediated mRNA decay' (NMD). We report here molecular analysis of smg-5, which encodes a novel protein required for NMD in Caenorhabditis elegans. Using a combination of immunoprecipitation and yeast two-hybrid assays, we identified a series of protein-protein interactions involving SMG-5. SMG-5 interacts with at least four proteins: (i) SMG-7, a previously identified protein required for NMD; (ii) SMG-2, a phosphorylated protein required for NMD in worms, yeasts and mammals; (iii) PR65, the structural subunit of protein phosphatase 2A (PP2A); and (iv) PP2A(C), the catalytic subunit of PP2A. Previous work demonstrated that both SMG-5 and SMG-7 are required for efficient dephosphorylation of SMG-2. Our results suggest that PP2A is the SMG-2 phosphatase, and the role of SMG-5 is to direct PP2A to its SMG-2 substrate. We discuss cycles of SMG-2 phosphorylation and their roles in NMD.
Anders
Kirk R
KR
Department of Genetics, University of Wisconsin-Madison, Madison, WI 53706, USA.
Grimson
Andrew
A
Anderson
Philip
P
D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D017238:Genes, Helminth; D015801:Helminth Proteins / Q000378:metabolism*; D010641:Phenotype; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D054648:Protein Phosphatase 2; D018510:RNA, Helminth / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D015801:Helminth Proteins; D010750:Phosphoproteins; D018510:RNA, Helminth; D012333:RNA, Messenger; C121027:SMG-2 protein, C elegans; C472410:SMG-5 protein, C elegans; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2