The UGA-A tetranucleotide is preferentially read through by tryptophan nc-tRNA and the UGA-C, and UGA-G tetranucleotides are preferentially read through by cysteine nc-tRNA. (A) Schematics of Trp and Cys nc-tRNAs base-paring with the indicated stop codon tetranucleotides. Only the nucleotides of the anticodon loop are shown with the third stop codon base N34 (in gray) and N32 indicated. (B) Effect of the eIF3 presence in pre-TCs on UGA-N readthrough upon increased gene dosage of tryptophan nc-tRNA. The PBH140 derivatives bearing TIF35 wt and tif35-KLF mutant alleles were transformed with either empty vector (EV) or high copy (hc) tW(CCA)G1 and the resulting transformants were grown and processed for stop codon readthrough measurements as described in Figure 1. (C) Effect of the eIF3 presence in pre-TCs on UGA-N readthrough upon increased gene dosage of cysteine nc-tRNA. Essentially the same as in B, except that hc tC(GCA)P1 was used in place of hc tW(CCA)G1.
