Unusual bipartite mode of interaction between the nonsense-mediated decay factors, UPF1 and UPF2

AUTOR(ES)

Clerici, Marcello

FONTE

Nature Publishing Group

RESUMO

Nonsense-mediated decay (NMD) is a eukaryotic quality control mechanism that degrades mRNAs carrying premature stop codons. In mammalian cells, NMD is triggered when UPF2 bound to UPF3 on a downstream exon junction complex interacts with UPF1 bound to a stalled ribosome. We report structural studies on the interaction between the C-terminal region of UPF2 and intact UPF1. Crystal structures, confirmed by EM and SAXS, show that the UPF1 CH-domain is docked onto its helicase domain in a fixed configuration. The C-terminal region of UPF2 is natively unfolded but binds through separated α-helical and β-hairpin elements to the UPF1 CH-domain. The α-helical region binds sixfold more weakly than the β-hairpin, whereas the combined elements bind 80-fold more tightly. Cellular assays show that NMD is severely affected by mutations disrupting the beta-hairpin binding, but not by those only affecting alpha-helix binding. We propose that the bipartite mode of UPF2 binding to UPF1 brings the ribosome and the EJC in close proximity by forming a tight complex after an initial weak encounter with either element.

Documentos Relacionados

• Upf1p, Nmd2p, and Upf3p are interacting components of the yeast nonsense-mediated mRNA decay pathway.
• Interaction between Ski7p and Upf1p is required for nonsense-mediated 3′-to-5′ mRNA decay in yeast
• Boundary-independent polar nonsense-mediated decay
• Identification of a Human Decapping Complex Associated with hUpf Proteins in Nonsense-Mediated Decay
• Nonsense-Mediated Decay of Human HEXA mRNA