Abstract
Aptamers are promising gene components that can be used for the construction of synthetic gene circuits. In this study, we isolated an RNA aptamer that specifically inhibits transcription of T7 RNA polymerase (RNAP). The 38‐nucleotide aptamer, which was a shortened variant of an initial SELEX isolate, showed moderate inhibitory activity. By stepwise doped‐SELEX, we isolated evolved variants with strong inhibitory activity. A 29‐nucleotide variant of a doped‐SELEX isolate showed 50% inhibitory concentration at 11 nM under typical in vitro transcription conditions. Pull‐down experiments revealed that the aptamer inhibited the association of T7 RNAP with T7 promoter DNA.