RNA Switches Using Cas Proteins.

Expanding the number of available RNA-binding proteins (RBPs) is vital to establishing posttranscriptional circuits in mammalian cells. We focused on CRISPR-Cas systems and exploited Cas proteins for their versatility as RBPs. The translation of genes encoded in an mRNA becomes regulatable by a Cas protein by inserting a crRNA/sgRNA sequence recognizable by the specific Cas protein into its 5'UTR.

Programmable mammalian translational modulators by CRISPR-associated proteins.

Translational modulation based on RNA-binding proteins can be used to construct artificial gene circuits, but RNA-binding proteins capable of regulating translation efficiently and orthogonally remain scarce. Here we report CARTRIDGE (Cas-Responsive Translational Regulation Integratable into Diverse Gene control) to repurpose Cas proteins as translational modulators in mammalian cells. We demonstrate that a set of Cas proteins efficiently and orthogonally repress or activate the translation of designed mRNAs that contain a Cas-binding RNA motif in the 5'-UTR.

A versatile and robust cell purification system with an RNA-only circuit composed of microRNA-responsive ON and OFF switches.

Human induced pluripotent stem cells (iPSCs) are promising cell resources for cell therapy and drug discovery. However, iPSC-derived differentiated cells are often heterogenous and need purification using a flow cytometer, which has high cost and time consumption for large-scale purification. MicroRNAs (miRNAs) can be used as cell selection markers, because their activity differs between cell types.

RNA and protein-based nanodevices for mammalian post-transcriptional circuits.

Mammalian synthetic gene circuits have promise in biological and medical research due to their capability of controlling cellular functions. Especially, post-transcriptional circuits are growing in interest because of features that include compatibility and superior safety. RNA-based molecular nanodevices are often a core component in these circuits.

Cell-Type-Specific CRISPR Activation with MicroRNA-Responsive AcrllA4 Switch.

Anti-CRISPR proteins have the potential to regulate CRISPR-Cas systems in a cell-type-specific manner. To selectively edit the genome in target cells, we controlled the expression of AcrllA4, a Cas9 inhibitor, based on endogenous microRNA (miRNA) activity. We designed a miRNA-responsive AcrllA4 switch, which is a synthetic mRNA that contains a completely complementary sequence to an arbitrary miRNA at the 5'-UTR region and encodes .

Cell-type-specific genome editing with a microRNA-responsive CRISPR-Cas9 switch.

The CRISPR-Cas9 system is a powerful genome-editing tool useful in a variety of biotechnology and biomedical applications. Here we developed a synthetic RNA-based, microRNA (miRNA)-responsive CRISPR-Cas9 system (miR-Cas9 switch) in which the genome editing activity of Cas9 can be modulated through endogenous miRNA signatures in mammalian cells. We created miR-Cas9 switches by using a miRNA-complementary sequence in the 5΄-UTR of mRNA encoding Streptococcus pyogenes Cas9.