Structural Basis of the PNRC2-Mediated Link between mRNA Surveillance and Decapping

• Published in: Structure (London) Vol. 20; no. 12; pp. 2025 - 2037
• Main Authors: Lai, Tingfeng, Cho, Hana, Liu, Zhou, Bowler, Matthew W., Piao, Shunfu, Parker, Roy, Kim, Yoon Ki, Song, Haiwei
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 05.12.2012
• Subjects: Amino Acid Sequence; Amino Acid Substitution; Binding Sites; Binding, Competitive; Crystallography, X-Ray; Endoribonucleases - chemistry; Endoribonucleases - genetics; Endoribonucleases - metabolism; HEK293 Cells; Humans; Hydrogen Bonding; Hydrophobic and Hydrophilic Interactions; Models, Molecular; Molecular Sequence Data; Mutagenesis, Site-Directed; Nonsense Mediated mRNA Decay; Protein Binding; Protein Interaction Domains and Motifs; Protein Structure, Secondary; Protein Transport; Receptors, Cytoplasmic and Nuclear - chemistry; Receptors, Cytoplasmic and Nuclear - genetics; Receptors, Cytoplasmic and Nuclear - metabolism; RNA, Messenger - chemistry; RNA, Messenger - genetics; RNA, Messenger - metabolism; Structural Homology, Protein; Trans-Activators - chemistry; Trans-Activators - genetics; Trans-Activators - metabolism
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2012.09.009

Nonsense-mediated mRNA decay (NMD) is an important mRNA surveillance system, and human PNRC2 protein mediates the link between mRNA surveillance and decapping. However, the mechanism by which PNRC2 interacts with the mRNA surveillance machinery and stimulates NMD is unknown. Here, we present the crystal structure of Dcp1a in complex with PNRC2. The proline-rich region of PNRC2 is bound to the EVH1 domain of Dcp1a, while its NR-box mediates the interaction with the hyperphosphorylated Upf1. The mode of PNRC2 interaction with Dcp1a is distinct from those observed in other EVH1/proline-rich ligands interactions. Disruption of the interaction of PNRC2 with Dcp1a abolishes its P-body localization and ability to promote mRNA degradation when tethered to mRNAs. PNRC2 acts in synergy with Dcp1a to stimulate the decapping activity of Dcp2 by bridging the interaction between Dcp1a and Dcp2, suggesting that PNRC2 is a decapping coactivator in addition to its adaptor role in NMD. ► PNRC2 binds to the EVH1 domain of Dcp1a via a distinct recognition mechanism ► The PRS and the NR-box regions of PNRC2 bind to Dcp1a and phospho-Upf1, respectively ► Dcp1a/PNRC2 interaction is critical for P-body localization and tethered mRNA decay ► PNRC2 is a decapping activator, acting in synergy with Dcp1a to activate decapping The mechanism of decapping enzyme recruitment and activation during nonsense-mediated mRNA decay (NMD) remains elusive. Lai et al. characterize factors involved in NMD and show that PNRC2 binds to both Dcp1a and the key NMD factor Upf1, thereby connecting the decapping enzyme with the mRNA surveillance machinery.