Development of a new-type riboswitch using an aptazyme and an anti-RBS sequence

We constructed a new-type riboswitch, which functions in E. coli, using an aptazyme and an anti-RBS sequence. This riboswitch usually suppresses the gene expression with its anti-RBS sequence bound to the RBS of its own mRNA(OFF), while it activates the translation only when a cofactor of the aptazyme is added to release the anti-RBS sequence from itself as a result of cofactor-induced self-cleavage by the aptazyme (ON). Although this aptazyme-based riboswitch did not function at 37 degrees C in vivo in spite of its high activity at this temperature in vitro, it worked well at lower temperature (23 degrees C). We also improved the efficiency of this riboswitch by constructing a cascading system.