Transcription reaction by T7-RNA polymerase was photo-regulated on the basis of two strategies as depicted in Scheme 1. It was found that incorporation reaction of azobenzene-tethered uridine triphosphate proceeded only when azobenzene took trans-form (Scheme 1(A)). On the other hand, the transcription was more efficient when the azobenzene moiety, tethered to the non-template strand of the promoter DNA, was in its cis-form under UV irradiation (Scheme 1(B)). Thus, azobenzene-tethered DNAs are promising for the photo-regulation of gene-expression.