Helix-Slipping
Helix-slipping uses a sequence that forms an imperfectly paired double-stranded stem that is flexible in its nucleotide base-pairing through a "slip-structure" mechanism. It does not allow for rational design and results in disruption or restoration of the hammerhead ribozyme in response to changes in the aptamer.
http://www.pnas.org/content/vol104/issue36/images/large/zpq0340773700003.jpeg
Figure 4. "Regulatory properties of the strand-displacement information transmission mechanism. The color scheme corresponds to that used in Fig. 1 with the following exceptions: switching strand, red; competing strand, green. (A) Gene expression ON ribozyme switch platform, L2bulge1. (B) Gene expression OFF ribozyme switch platform, L2bulgeOff1. (C and D) The theophylline-dependent gene-regulatory behavior of L2bulge1 (ON switch) (C), L2bulgeOff1 (OFF switch) (D), and L2Theo (nonswitch control). Gene-expression levels are reported in fold as defined in SI Text and were normalized to the expression levels in the absence of effector." (Win and Smolke, 2007). Image Permission Pending.
