(A) Readthrough efficiencies determined by dual luciferase assay after transfection of HEK293T cells with either pSGDluc (light gray) or pDluc (dark gray) harboring readthrough signals from human SACM1L, ACP2-1, ACP2-2, BRI3BP, MDH, LDH, and VEGFA, as indicated. Readthrough efficiency of UGA_C cloned into pSGDluc representing background levels of readthrough on UGA_C is indicated by a dashed line. (B) Predicted RNA stem–loop structure immediately 3′ of the ACP2 CDS indicating the 3′ boundaries of readthrough signals for ACP2-1 and ACP2-2. The second stop codon was mutated to UGG in construct ACP2-2. Stop codons are in red font.