Fig. 1.

(A) Transcriptional base substitution in the luciferase gene for the study of SN-BER. The codon 27 of the luciferase gene was modified to a stop codon by introduction of a uracil residue, as indicated. The uracil will be converted to a leucine codon after DNA repair, resulting in luciferase protein expression. (B) The construction of plasmid DNA containing uracil is described under “Materials and methods.” The Renilla luciferase gene of pGL4.75 was replaced by the Chroma-Luc™ gene, and the oligonucleotide fragment containing uracil was ligated at the BsaXI site introduced by site-directed mutagenesis in the Chroma-Luc™ gene. (C) Confirmation of plasmid preparations. Plasmids AM1, AM1-P (positive) and AM1-U (uracil) were treated with BsaXI at 37°C for 1 h, and then the mixtures were analyzed by 1% agarose gel electrophoresis. AM1 was used as reference for closed circular (lane 1) and linear DNA (lane 2).