Fig. 1. Construction and evaluation of a light-activated promoter.

(A) T7 RNA polymerase is blocked from binding to the LA-T7 promoter due to the presence of multiple monovalent streptavidins, bound to the DNA through biotinylated PC linkers. Following UV light cleavage of the linkers, T7 RNA polymerase can transcribe the downstream gene. (B) LA-T7 promoter sequence. Pink-colored thymines are replaced with amino-C6-dT modifications and the primary amines of the nucleobase coupled to the PC biotin group. (C) LA-DNA encoding for mVenus is only expressed upon UV irradiation. There is no significant difference between expression from the LA-DNA (+UV) and expression from the amine-only DNA construct. a.u., arbitary unit.