title: Upf1 potentially serves as a RING-related E3 ubiquitin ligase via its association with Upf3 in yeast.
abstract: Three Upf proteins are essential to the nonsense-mediated mRNA decay (NMD) pathway. Although these proteins assemble on polysomes for recognition of aberrant mRNAs containing premature termination codons, the significance of this assembly remains to be elucidated. The Cys- and His-rich repeated N terminus (CH domain) of Upf1 has been implicated in its binding to Upf2. Here, we show that CH domain also plays a RING-related role for Upf1 to exhibit E3 ubiquitin ligase activity in yeast. Despite the sequence divergence from typical E3-RING fingers, the CH domain of yeast Upf1 specifically and directly interacted with the yeast E2 Ubc3. Interestingly, Upf1 served as a substrate for the in vitro self-ubiquitination, and the modification required its association with Upf3 rather than Upf2. Substitution of the coordinated Cys and His residues in the CH domain impaired not only self-ubiquitination of Upf1 but also rapid decay of aberrant mRNAs. These results suggest that Upf1 may serve as an E3 ubiquitin ligase upon its association with Upf3 and play an important role in signaling to the NMD pathway.
authors.affiliation: Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan
authors.forename: Shinya
authors.initials: S
authors.lastname: Takahashi
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Araki
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Ohya
authors.forename: Takeshi
authors.initials: T
authors.lastname: Sakuno
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Hoshino
authors.forename: Kenji
authors.initials: K
authors.lastname: Kontani
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nishina
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Katada
mesh_terms: D000595:Amino Acid Sequence; D018389:Codon, Nonsense / Q000378:metabolism; D008969:Molecular Sequence Data; D054829:RING Finger Domains; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism*; D020871:RNA Stability; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D018389:Codon, Nonsense; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; C096360:UPF3 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases; C074151:NAM7 protein, S cerevisiae; D020365:RNA Helicases