The present disclosure relates to viral delivery of RNA utilizing self-cleaving ribozymes and applications of such, including but not limited to CRISPR-Cas related applications.

The present invention relates to a nucleic acid cassette for improved genome editing by transiently silencing non-homologous end joining (NHEJ) and/or microhomology-mediated end joining (MMEJ) pathways during the editing process. A nucleic acid cassette according to the invention comprises (a) at least one RNA interference (RNAi) component, (b) at least one CRISPR guide RNA component and (c) at least one RNA activating unit, wherein the nucleic acid cassette is suitable for the simultaneous expression of at least one sequence encoding an RNA interference (RNAi) component and at least one sequence encoding a CRISPR guide RNA component. The invention further provides methods for modification of at least one genomic target sequence in a cell, wherein a nucleic acid cassette according to the invention and an RNA-guided site-specific nuclease is introduced in the cell and editing of the target sequence takes place while NHEJ and/or MMEJ pathways are silenced.

Aspects of the disclosure relate to methods and compositions useful for treating retinitis pigmentosa. In some aspects, the disclosure provides compositions and methods for delivering an interfering RNA to a subject in order to reduce expression of one or both alleles of an endogenous RHO gene (for example a mutant rho allele associated with retinitis pigmentosa) in a subject. In some embodiments, a replacement RHO coding sequence that is resistant to the interfering RNA also is delivered to the subject.

The present disclosure relates to viral delivery of RNA utilizing self-cleaving ribozymes and applications of such, including but not limited to CRISPR-Cas related applications.

A CRISPR/Cas system and method for editing or regulating transcription of a genome of a cell are provided, wherein the system includes a Cas endonuclease fused with one or more degron sequences and at least one activatable cognate single guide RNA harboring an inactivation sequence in a non-essential region of the cognate sgRNA, wherein said inactivation sequence comprises one or more endonuclease recognition sites of, e.g., a ribozyme.

A ligand-responsive hammerhead ribozyme is provided. In some embodiments, the ribozyme comprises: i. a first loop that has been replaced by an RNA aptamer that binds to a ligand; and ii. a second loop comprising a modified sequence, wherein the aptamer and the second loop interact in a ligand-dependent manner and autocatalytic cleavage of the ribozyme is ligand-responsive.

The presently disclosed subject matter provides compositions and methods for the expression of CRISPR guide RNAs using the H1 promoter. In particular, compositions and methods are provided for the use of the H1 promoter to express CRISPR guide RNA (gRNA) with altered specificity of the 5 nucleotide, as well as use of the H1 promoter sequence as a bidirectional promoter to express Cas9 nuclease and the gRNA simultaneously. Compositions and methods are also provided for the expression and regulation of gRNA expression in vivo through the use of RNA ribozymes and regulatable aptazymes.

Aptamers that specifically bind to ligands of folinic acid, a folate, and derivatives thereof (which may be referred to herein as ligands) are provided, and compositions and methods of use thereof. The aptamers and switches of the invention provide biological sensing capability for detecting the ligands, and are effective in sensing in vitro and in vivo. By specific sensing of the ligand, the aptamers of the invention provide a means of engineering an inducible gene regulatory system that enables dose-dependent control over gene expression in response to the ligand, in vivo and in vitro.

Non-conventional yeasts are disclosed herein comprising at least one RNA-guided endonuclease (RGEN) comprising at least one RNA component that does not have a 5-cap. This uncapped RNA component comprises a sequence complementary to a target site sequence in a chromosome or episome in the yeast. The RGEN can bind to, and optionally cleave, one or both DNA strands at the target site sequence. An example of an RGEN herein is a complex of a Cas9 protein with a guide RNA. A ribozyme is used in certain embodiments to provide an RNA component lacking a 5-cap. Further disclosed are methods of genetic targeting in non-conventional yeast.

Some aspects of this disclosure provide compositions, methods, systems, and kits for controlling the activity and/or improving the specificity of RNA-programmable proteins, such as Cas9. For example, provided are guide RNAs (gRNAs) that are engineered to exist in an on or off state, which control the binding and, in certain instances, cleavage activity of RNA-programmable proteins (e.g., RNA-programmable endonucleases). By incorporating ligand-responsive self-cleaving catalytic RNAs (aptazymes) into guide RNAs, a set of aptazyme-embedded guide RNAs was developed that enable small molecule-controlled nuclease-mediated genome editing and small molecule-controlled base editing, as well as small molecule-dependent transcriptional activation in mammalian cells.