N- and C-terminal Upf1 phosphorylations create binding platforms for SMG-6 and SMG-5:SMG-7 during NMD

Nucleic Acids Res. 2012 Feb;40(3):1251-66. doi: 10.1093/nar/gkr791. Epub 2011 Sep 29.

Abstract

Nonsense-mediated mRNA decay (NMD) is a surveillance mechanism that detects and degrades mRNAs containing premature termination codons (PTCs). SMG-1-mediated Upf1 phosphorylation takes place in the decay inducing complex (DECID), which contains a ribosome, release factors, Upf1, SMG-1, an exon junction complex (EJC) and a PTC-mRNA. However, the significance and the consequence of Upf1 phosphorylation remain to be clarified. Here, we demonstrate that SMG-6 binds to a newly identified phosphorylation site in Upf1 at N-terminal threonine 28, whereas the SMG-5:SMG-7 complex binds to phosphorylated serine 1096 of Upf1. In addition, the binding of the SMG-5:SMG-7 complex to Upf1 resulted in the dissociation of the ribosome and release factors from the DECID complex. Importantly, the simultaneous binding of both the SMG-5:SMG-7 complex and SMG-6 to phospho-Upf1 are required for both NMD and Upf1 dissociation from mRNA. Thus, the SMG-1-mediated phosphorylation of Upf1 creates a binding platforms for the SMG-5:SMG-7 complex and for SMG-6, and triggers sequential remodeling of the mRNA surveillance complex for NMD induction and recycling of the ribosome, release factors and NMD factors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 14-3-3 Proteins / chemistry
  • Binding Sites
  • Carrier Proteins / metabolism*
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Nonsense Mediated mRNA Decay*
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphorylation
  • Protein Structure, Tertiary
  • Protein-Serine-Threonine Kinases
  • RNA Helicases
  • Telomerase / chemistry
  • Telomerase / metabolism*
  • Threonine / physiology
  • Trans-Activators / chemistry
  • Trans-Activators / metabolism*

Substances

  • 14-3-3 Proteins
  • Carrier Proteins
  • SMG5 protein, human
  • SMG7 protein, human
  • Trans-Activators
  • Threonine
  • Protein-Serine-Threonine Kinases
  • SMG1 protein, human
  • SMG6 protein, human
  • Telomerase
  • RNA Helicases
  • UPF1 protein, human