Just found this. A ribozyme that cleaves itself, unless it binds tetracyclin. Proven to work in mammalian cells.
You just have to embedd this ribozyme into a mRNA, ideally direcly after the stop codon (3’UTR). CAAA3 is used as a spacer so the ribozyme folding is more smooth, presumably because A-T binding is a lot weaker than G-C.
Seems to be very helpful when you want to use tetracycline to activate gene expression but you don’t want to introduce foreign proteins (such as the tet-transcativator that then binds a tet-operator-CMV Promoter). Without tetracycline in the medium, the mRNA cleaves itself and you get only ~25% of the expression because mRNA without a polyA tail is rapidly degraded. When you add 50 uM tet, the ribozyme is prevented from cutting itself and you get the full expression.


The ribozyme is described in the study “Conditional Control of Mammalian Gene Expression by Tetracycline-Dependent Hammerhead Ribozymes” by Kim Beilstein, Alexander Wittmann, Manuel Grez, and Beatrix Suess. I had ty type it in from the graphic, always annowing when the full sequence isn’t given in a format that’s copyable.3k4-tet-ribozyme

Alledgedly there is a better ribozyme from the study “Rational design of aptazyme riboswitches for efficient control of gene expression in mammlian cells” that has 20 fold repression wiothout tetracyclin. Unfortunately they hid their sequence very well in the paper and I have to reverse engineer all of their paper to find the sequence they used. #moretransparencyinqualityjournalsplease


EDIT: The author of  “Rational design of aptazyme riboswitches for efficient control of gene expression in mammlian cells” has kindly replied to my email the next day. He provided the sequences:





Yellow/orange:aptazyme sequence

Bold underlined: communication module