Synthetic gene involving azobenzene-tethered T7 promoter for the photocontrol of gene expression by visible light.

In the present study, we demonstrate photoregulation of gene expression in a cell-free translation system from a T7 promoter containing two azobenzene derivatives at specific positions. As photoswitches, we prepared azobenzene-4'-carboxlyic acid (Azo) and 2,6-dimethylazobenzene-4'-carboxylic acid (DM-Azo), which were isomerized from trans to cis upon irradiation with UV light (λ < 370 nm), and 4-methylthioazobenzene-4'-carboxylic acid (S-Azo) and 2,6-dimethyl-4-(methylthio)azobenzene-4'-carobxylic acid (S-DM-Azo), which were cis-isomerized by irradiation with 400 nm visible light. Expression of green fluorescent protein from a promoter modified with S-Azo or S-DM-Azo could be induced by harmless visible light whereas that from a promoter modified with Azo or DM-Azo was induced only by UV light (340-360 nm). Thus, efficient photoregulation of green fluorescent protein production was achieved in a cell-free translation system with visible light without photodamage.