Figure 1

AβMRF causes nonsense suppression in yeast. (Upper panel) Schematic illustration of the constructs used in this study: (a) full length Sup35p (NMRF) (b) Sup35p without the N-terminal prion domain (MRF) (c) Aβ₄₂ fused to the N terminus of MRF (AβMRF) (d) AβMRF carrying a double mutation of Phe19,20Thr in its Aβ₄₂ portion (Aβm1MRF) (e) AβMRF carrying a triple mutation of Phe19,20Thr and Ile31Pro in its Aβ₄₂ portion (Aβm2MRF). All these constructs carry an HA tag between the M and RF domains. Images shown are not to scale. (Lower panel) Equal numbers of ade1-14 cells containing a genomic deletion of SUP35 (sup35Δ), and carrying the indicated constructs (a-e) on a plasmid were grown on complex medium, or synthetic medium supplemented (+Ade) or not (-Ade) with adenine. (a) Cells with inactivated NMRF ([PSI+]) had an impaired translational termination activity, were white and grew on -Ade. (b) Cells with fully active MRF (lacking the aggregation-prone prion, N, domain), were red and failed to grow on -Ade. (c) Cells expressing AβMRF have an impaired translational termination activity, as they were white and grew on -Ade. (d, e) The translational termination activity was restored by F19,20T (Aβm1MRF) and F19,20T/I31P (Aβm2MRF) mutations in the Aβ42 region of the fusion protein, making the cells dark pink and preventing their growth on -Ade.