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Phosphorylation of the N ‐ and C ‐terminal UPF 1 domains plays a critical role in plant nonsense‐mediated m RNA decay
Author(s) -
Kerényi Farkas,
Wawer Izabela,
Sikorski Pawel J.,
Kufel Joanna,
Silhavy Dániel
Publication year - 2013
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12346
Subject(s) - phosphorylation , nonsense mediated decay , context (archaeology) , microbiology and biotechnology , mutant , biology , stop codon , c terminus , rna , chemistry , biochemistry , amino acid , gene , rna splicing , paleontology
Summary Nonsense‐mediated m RNA decay ( NMD ) is an essential quality control system that degrades aberrant transcripts containing premature termination codons and regulates the expression of several normal transcripts. Targets for NMD are selected during translational termination. If termination is slow, the UPF 1 NMD factor binds the e RF 3 protein of the termination complex and then recruits UPF 2 and UPF 3. Consequently, the UPF 1‐2‐3 NMD complex induces SMG 7‐mediated degradation of the target m RNA . It is unknown how formation of the NMD complex and transcript degradation are linked in plants. Previously we have shown that the N ‐ and C ‐terminal domains of UPF 1 act redundantly and that the N‐terminal domain is phosphorylated. To clarify the role of UPF 1 phosphorylation in plant NMD , we generated UPF 1 mutants and analyzed their phosphorylation status and the NMD competency of the mutants. We show that although several residues in the N ‐terminal domain of UPF 1 are phosphorylated, only three phosphorylated amino acids, S 3, S 13 and T 29, play a role in NMD . Moreover, we found that the C ‐terminal domain consists of redundant S / TQ ‐rich segments and that S 1076 is involved in NMD . All NMD ‐relevant phosphorylation sites were in the S / TQ context. Co‐localization and fluorescence resonance energy transfer–fluorescence lifetime imaging assays suggest that N ‐terminal and probably also C ‐terminal phosphorylated S / TQ residues are the binding platform for SMG 7. Our data support the hypothesis that phosphorylation of UPF 1 connects NMD complex formation and the SMG 7‐mediated target transcript degradation steps of NMD . SMG 7 binds the phosphorylated S / TQ sites of the UPF 1 component of the NMD complex, and then it induces the degradation of the NMD target.

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