title: Role for Upf2p phosphorylation in Saccharomyces cerevisiae nonsense-mediated mRNA decay.
abstract: Premature termination (nonsense) codons trigger rapid mRNA decay by the nonsense-mediated mRNA decay (NMD) pathway. Two conserved proteins essential for NMD, UPF1 and UPF2, are phosphorylated in higher eukaryotes. The phosphorylation and dephosphorylation of UPF1 appear to be crucial for NMD, as blockade of either event in Caenorhabditis elegans and mammals largely prevents NMD. The universality of this phosphorylation/dephosphorylation cycle pathway has been questioned, however, because the well-studied Saccharomyces cerevisiae NMD pathway has not been shown to be regulated by phosphorylation. Here, we used in vitro and in vivo biochemical techniques to show that both S. cerevisiae Upf1p and Upf2p are phosphoproteins. We provide evidence that the phosphorylation of the N-terminal region of Upf2p is crucial for its interaction with Hrp1p, an RNA-binding protein that we previously showed is essential for NMD. We identify specific amino acids in Upf2p's N-terminal domain, including phosphorylated serines, which dictate both its interaction with Hrp1p and its ability to elicit NMD. Our results indicate that phosphorylation of UPF1 and UPF2 is a conserved event in eukaryotes and for the first time provide evidence that Upf2p phosphorylation is crucial for NMD.
authors.affiliation: Department of Biology, University of Puerto Rico, San Juan, PR 00931.
authors.forename: Weirong
authors.initials: W
authors.lastname: Wang
authors.forename: Iván J
authors.initials: IJ
authors.lastname: Cajigas
authors.forename: Stuart W
authors.initials: SW
authors.lastname: Peltz
authors.forename: Miles F
authors.initials: MF
authors.lastname: Wilkinson
authors.forename: Carlos I
authors.initials: CI
authors.lastname: González
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D018389:Codon, Nonsense / Q000378:metabolism*; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D020365:RNA Helicases / Q000378:metabolism; D020871:RNA Stability / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D039221:mRNA Cleavage and Polyadenylation Factors / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018389:Codon, Nonsense; C092470:NMD2 protein, S cerevisiae; D010750:Phosphoproteins; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D039221:mRNA Cleavage and Polyadenylation Factors; C074151:NAM7 protein, S cerevisiae; D020365:RNA Helicases