Azobenzene-tethered T7 promoter for efficient photoregulation of transcription

Azobenzene was additionally introduced into side chain of T7 promoter for the photocontrol of transcription reaction by T7 RNA polymerase (T7 RNAP). When a single azobenzene molecule was introduced into the T7 promoter either at the loop-binding region of the RNAP (−7 to −11 position) or at the unwinding region (−1 to −4 position), transcription was suppressed in the trans-form but proceeded faster in the cis-form. The amount of transcripts after UV irradiation with respect to that in the dark was 1.5−2.0-fold. Kinetic analysis of the transcription reaction revealed that the photoregulatory mechanism was different in these positions. The photoisomerization of an azobenzene at the loop-binding region primarily affected Km. On the other hand, the isomerization of an azobenzene at the unwinding region mainly affected kcat. Still more clear-cut photoregulation was achieved when two azobenzenes were introduced into both loop-binding and unwinding regions, respectively:  transcription proceeded 7.6-fold faster ...