The yef3-fs1009 mutation suppresses frameshifting with two different inhibitory codon combinations, but has only small effects on in-frame expression of reporters with optimal or inhibitory codons. (A) Schematic of RFP and GLN4(1–99)-codon insert-GFP reporters used in these analyses. (B) The yef3-fs1009 mutation suppresses frameshifting in a mbf1-R89K mutant bearing a reporter with three copies of CGA–CGA codon pairs but does not relieve or enhance CGA inhibition from in-frame reporters. Levels of GFP/RFP protein (fluorescence), mRNA and protein/mRNA are similar from in-frame reporters with optimal (AGA–AGA) or inhibitory (CGA–CGA) codon pairs, but levels of protein and protein/mRNA levels are significantly different from the analogous frameshifted reporter with a (CGA–CGA)3 +1 insert. In-frame expression of inhibitory (CGA) reporter relative to optimal (AGA) reporter is shown below. (C) The yef3-fs1009 mutation suppresses frameshifting in an mbf1-R89K mutant with a reporter bearing a single CGA–CGG inhibitory pair, but does not affect CGA–CGG inhibition. In-frame expression of inhibitory (CGA–CGG) reporters relative to optimal (AGA–AGA) reporters is similar in YEF3 and the yef3-fs1009 mutant strains (table), although levels of GFP/RFP protein and protein/mRNA from both in-frame reporters are greater in the yef3-fs1009 mutant. In contrast, both GFP/RFP protein and protein/mRNA levels from the frameshifted reporter are reduced in the yef3-fs1009 mutant. (D) The yef3-fs1009 mutation suppresses frameshifting in an mbf1Δ mutant with a reporter bearing a single CGA–CGG inhibitory pair. (**) P < 0.01 ≥ 0.001. (***) P < 0.001.
