Nonsense mutations in the SUP45 gene confer the viability in the different genetic backgrounds. A. Strain 1A-D1628 bearing SUP45 disruption was co-transformed by pRS316/SUP45 and pRS315/sup45-n plasmids. The cotransformants bearing pRS316/SUP45 and vector pRS315 only were used as a negative control. The transformants were assayed for growth by plating on 5-FOA medium to select against the URA3 plasmid pRS316/SUP45 carrying a wild-type copy of SUP45. Ten serial dilutions of yeast suspensions of the same density were used. Five independent transformants for each combination were tested. Representative results are shown. B. Plate assays showing the growth of transformants of 1A-D1628 bearing pRS316/SUP45 or pRS316/sup45-n plasmids on the synthetic medium without adenine (SC-Ade) or tryptophan (SC-Trp) at 25°C. The strains were tested in the same way as in Fig. 2A. C. Western blot showing the expression of full-length eRF1 (49 kDa) and truncated eRF1 proteins in the same strains as in (B). D. Complementation of the SUP45 gene disruption in the strain 13A-Y23282 by sup45-n mutations. The transformants with vector pRS315 were used as a negative control. The same plasmids as in (A) were used.