Japanese scientists have designed a DNA nanostructure that mechanically controls gene transcription (J. Am. Chem. Soc., DOI: 10.1021/ja2074856). Hiroshi Sugiyama, Masayuki Endo, and coworkers at Kyoto University attached a tubular DNA nanostructure to a double-stranded DNA template containing a promoter region that is enclosed in the tube. The tube also has single-stranded DNA called toehold strands. When complementary DNA binds to these toehold strands, the tube opens, exposing the promoter region and giving RNA polymerase access to the template. With the structure open, the researchers observe a more than fivefold jump in gene transcription, compared with when the structure is closed. Because a low level of transcription occurs even when the tube is closed, the mechanism may not completely block RNA polymerase binding to the template. The system could be used to control the expression of various biological reactions, the researchers note.