Application of synthetic biology and optogenetics to controlling gene expression

Abstract

Synthetic biology provides the platform and tools to design artificial regulators to control mRNA translation. In this work, we report a genetically encoded system to regulate mRNA translation using the Pumilio and FBF (PUF) domains in mammalian cells. PUF domain serves as a designable scaffold to recognize specific RNA elements, and the specificity can be altered easily to target any 8-nt RNA. In this system, the gene expression could be varied by over 17-fold when using PUF-based activators and repressors. The specificity of the method was established by using wild-type and mutant PUF domains.

Optogenetics is a technology that allows control of cellular events using visible light as the signal/inducer. We designed an optogenetic system that employs the light-sensitive dimerizing partners from Arabidopsis thaliana, Cryptochrome 2 (CRY2) and Cryptochrome-interacting basic-helix-loop-helix 1 (CIB1), to reconstitute an RNA binding peptide and a translation initiation protein, thereby activating target mRNA translation downstream of the binding sites. Moreover, the combination of the two technologies allows us to construct to a light-inducible gene expression system using PUF domains, which can be used to regulate cellular RNA functions in a light-sensitive manner.

Additionally, we found that PUF domains could also be used to repress mRNA translation in E. coli. Such a system adds an important tool of RNA/protein interaction into the repertoire of tools for genetic circuit construction in E. coli.

Considerable work has focused on the control of gene expression, motivated by both a fundamental interest in biological research as well as by applications ranging from gene therapy to metabolic engineering.