Guide RNA-Cas9 Targeting for Precise DNA Editing and Transcription Control
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Solution Overview
Problem
Current technologies for genetic manipulation, such as engineered nuclease enzymes, require designing new proteins for each target sequence, leading to time-consuming and costly processes with limited precision and significant off-target effects.
Innovation Solution
A DNA-targeting RNA comprising a targeting sequence and a modifying polypeptide, which allows for site-specific modification of target DNA and associated polypeptides without the need to design new proteins for each target sequence, using enzymatically inactive Cas9 polypeptide and DNA-targeting RNA to modulate transcription.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If engineered nuclease enzymes are designed to target specific DNA sequences, then site-specific DNA modification is achieved, but the process becomes time-consuming and costly due to requiring novel nuclease design for each target
Solution Approach 1:
The patent applies universality by using a single Cas9 nuclease enzyme that can target multiple different DNA sequences through exchange of guide RNA molecules. The Cas9 protein serves as a universal platform that, when combined with different crRNA-tracrRNA pairs, can recognize and cleave various target sequences without requiring redesign of the nuclease itself. This resolves the contradiction by maintaining high precision site-specific modification while eliminating the time-consuming process of designing new nucleases for each target.
Solution Approach 2:
The patent introduces guide RNA (crRNA-tracrRNA complex) as an intermediary that mediates between the Cas9 nuclease and the target DNA sequence. The guide RNA contains the sequence-specific recognition information, allowing the Cas9 enzyme to be directed to different genomic locations without structural modification. This intermediary mechanism enables rapid reprogramming of target specificity by simply changing the RNA sequence, thereby solving the time and resource inefficiency of redesigning nucleases for each target.
2Adaptability or versatility
If engineered nuclease enzymes are used for genetic manipulation, then targeted gene deletion and replacement is enabled, but off-target effects increase due to limited precision
Solution Approach 1:
The patent applies local quality by requiring two simultaneous recognition events for Cas9 activation: (1) binding of the guide RNA to the complementary DNA sequence, and (2) recognition of the adjacent protospacer adjacent motif (PAM) sequence by Cas9. This dual recognition mechanism ensures that cleavage occurs only at the precise location where both conditions are met, significantly reducing off-target effects while maintaining the versatility for targeted gene manipulation throughout the genome.
Solution Approach 2:
The system incorporates feedback through the PAM recognition requirement, which acts as a verification step before cleavage. The Cas9 enzyme must first bind to the PAM sequence, then recruit and validate the guide RNA-DNA hybrid formation before activating nuclease activity. This multi-step verification process provides a feedback mechanism that ensures high fidelity targeting and prevents spurious cleavage at off-target sites, thereby reducing harmful off-target effects while preserving genomic editing capability.
3Adaptability or versatility
If RNA interference is used to target arbitrary genes for regulation, then gene expression control is achieved, but off-target effects and toxicity increase
Solution Approach 1:
The patent replaces the RNA interference mechanism (which uses dsRNA to trigger degradation of complementary mRNA) with a CRISPR-Cas system that uses guide RNA to direct a nuclease to the DNA template. This substitution changes the mechanism from post-transcriptional mRNA degradation to direct genomic DNA cleavage or transcriptional interference, thereby achieving gene regulation with higher specificity and reduced off-target effects, as the DNA-level targeting is more precise than RNA-level targeting.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise targeting of nuclease activity or other protein activities to distinct locations within a target DNA, minimizing off-target effects and reducing the time and cost associated with genetic manipulation.
Implementation Method 1
a DNA-targeting RNA that comprises a targeting sequence... a first segment comprising a nucleotide sequence that is complementary to a sequence in a target DNA
Implementation Method 2
together with a modifying polypeptide, provides for site-specific modification of a target DNA... an activity portion that exhibits site-directed enzymatic activity
Data Source
AI summary
The present disclosure provides a DNA-targeting RNA that comprises a targeting sequence and, together with a modifying polypeptide, provides for site-specific modification of a target DNA and/or a polypeptide associated with the target DNA. The present disclosure further provides site-specific modifying polypeptides. The present disclosure further provides methods of site-specific modification of a target DNA and/or a polypeptide associated with the target DNA The present disclosure provides methods of modulating transcription of a target nucleic acid in a target cell, generally involving contacting the target nucleic acid with an enzymatically inactive Cas9 polypeptide and a DNA-targeting RNA. Kits and compositions for carrying out the methods are also provided. The present disclosure provides genetically modified cells that produce Cas9; and Cas9 transgenic non-human multicellular organisms.