Fig. 3. Trans effect of the prion-forming domain on Ure2p–GFP aggregation. The strain EG12 was transformed by a plasmid that overexpresses the prion-forming domain of Ure2p. (A) The transformed cells. (B) Clones of the EG12 strain selected for the Usa⁺ phenotype in which the characteristic aggregation pattern (indicated by arrows) is found in less than 1% of the cells. (C and D) Nomarski of the same cells. Bar, 10 µm.