Figure 7.
C-terminal mutations in eIF1A cause scanning/AUG recognition defects in vitro and in vivo. (A) Toe-printing analysis of 48S complexes on β-globin mRNA in reaction mixtures containing 40S subunits and mammalian translation initiation factors in the absence or presence of eIF1A, as indicated. See text for explanation of different complexes labeled on the left. (B) The 98–101 mutation increases utilization of a UUG start codon in vivo. Strains H3583 and H3584 carrying plasmids YCp50-HIS4-AUG-lacZ or YCp50-HIS4-UUG-lacZ were grown in SC-U medium and assayed for β-galactosidase activity. The specific activities±s.e. (n=6) determined for the YCp50-HIS4-UUG-lacZ versus YCp50-HIS4-AUG-lacZ transformants were measured in three independent experiments and used to calculate the mean ratios±s.e. (n=3) shown in the histogram. (C) The ΔC mutation suppresses the His− phenotype conferred by the his4-303 allele. Serial 10-fold dilutions of strains H3583 and H3586 were spotted on SC lacking leucine and histidine and grown at 30°C for 2 days (SC, upper panel) or 14 days (SC-H, lower panel).