Researchers in the lab of Professor Susan Rosser, Director of the UK Centre for Mammalian Synthetic Biology, have built drug-induced degradable variants of the gene-editing tool Cas9 to create an externally controllable system with greater dynamic for regulating gene expression.
Recent advances in the ability to engineer artificial transcription factors (proteins that can control transcription of target genes) have made it possible to design and build novel synthetic gene expression programs. In particular, a mutant version of the clustered, regularly interspaced, short palindromic repeats (CRISPR)-associated protein Cas9, in which the DNA cutting activity of the protein has been disabled (dCas9), has proved a powerful scaffold for the creation of transcription factors with desired functionalities. A variety of functional domains (e.g. activator or repressor domains) can be attached to dCas9 and used to switch on or off gene expression in mammalian cells. However, to date, this tends to result in a relatively stable system imposing a rather static environment on the regulatory circuits in the cells. What would be valuable is a way to create a system with potential for a higher turn-over of the engineered dCas9 proteins whose persistence in the cell could be tunably switched on or off using drugs.
To address this challenge Susan Rosser and post-docs Dirk-Jan Kleinjan, Caroline Wardrope and Si Nga (Susie) Sou have developed a toolkit of dCas9 (or its cousin protein Cpf1) effector proteins, for which protein stability can be modulated by administration of simple drugs, auxin and trimethoprim. In combination these drug-tunable artificial transcription factors can provide multidimensional control of functional activities in cells, which will benefit the construction of complex regulatory circuits with greater switching dynamics
Published in: Kleinjan, D., Wardrope, C., Sou, SN., Rosser SJ. Drug-tunable multidimensional synthetic gene control using inducible degron-tagged dCas9 effectors. Nature Communications 8, Article number: 1191 (2017)