Cytosine immediately following any stop codon interferes with the eRF1 decoding in vivo. (A) Stop codon readthrough measured at all four UGA-N termination tetranucleotides in wt cells (SUP45) and two eRF1 mutants (sup45-M48I and sup45-Y410S). The 74D-694, L2327, and L2521 strains were grown in SD and processed for stop codon readthrough measurements using standard dual luciferase readthrough reporter constructs YEp-R/T-CAAC-L; YEp-R/T-UGAC-L; PBB75; PBB76; and PBB77, as described in Materials and Methods. Readthrough values are represented as mean ± SD from quintuplicates (n = 5) and each experiment was repeated at least three times. (B) Normalization of readthrough measurements from panel A; values measured for UGA-U of each of the four strains were set to one. (C) Same as in panel A, except that all four UAA-N termination tetranucleotides were examined. (D) Same as in panel A, except that all four UAG-N termination tetranucleotides were examined.
