Modified Guide RNA Chemical Structure for CRISPR Stability
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Solution Overview
Problem
Current CRISPR-Cas systems face challenges in achieving specificity, stability, and reduced off-target effects while maintaining efficient transfectability and minimal immunostimulatory properties for gRNA, particularly in eukaryotic cells.
Innovation Solution
Chemical modifications to guide RNAs, such as nucleotide sugar and backbone modifications, are introduced to enhance stability, specificity, and binding affinity without compromising Cas:gRNA complex functionality, allowing for effective delivery and maintenance within cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical modifications are introduced to enhance gRNA stability and reduce degradation, then resistance to nucleolytic degradation is improved, but complexity of gRNA structure increases
Solution Approach 1:
The patent applies parameter changes by modifying the chemical structure of nucleotides within the gRNA molecule. Specifically, it incorporates nucleotide analogs with altered sugar moieties (such as 2'-O-methyl, 2'-fluoro, or locked nucleic acid modifications) and backbone modifications (such as phosphorothioate linkages). These chemical parameter changes enhance the gRNA's resistance to nucleolytic degradation while maintaining its ability to guide the Cas nuclease to the target sequence, thus improving reliability without fundamentally changing the functional mechanism.
Solution Approach 2:
The patent employs composite materials by creating a hybrid gRNA structure that combines modified nucleotides with unmodified nucleotides in specific regions. The gRNA consists of a modified scaffold region (providing structural stability and nuclease resistance) combined with a guide sequence region (maintaining target recognition). This composite approach allows different portions of the gRNA to have optimized properties: the scaffold uses chemically modified nucleotides for stability, while the guide sequence uses natural or minimally modified nucleotides for precise target binding.
2Measurement precision
If chemical modifications are introduced to improve target specificity and reduce off-target effects, then binding specificity is improved, but ease of manufacture decreases
Solution Approach 1:
The patent applies local quality by introducing chemical modifications selectively at specific positions within the gRNA structure rather than uniformly throughout. Modifications are concentrated in the scaffold region (particularly at positions known to interact with Cas proteins) while leaving the guide sequence region largely unmodified or minimally modified. This localized modification strategy enhances target specificity through improved Cas-gRNA complex stability without requiring complex synthesis protocols for the entire molecule, thus balancing manufacturing ease with specificity improvement.
3Strength
If chemical modifications are introduced to enhance binding affinity for target polynucleotide, then binding affinity is improved, but immunostimulatory properties may increase
Solution Approach 1:
The patent applies copying by using nucleotide analogs that closely resemble natural nucleotides in their overall structure and bonding properties. The modified nucleotides (such as 2'-O-methyl or LNA) maintain the fundamental ribose-phosphate-base structure that is recognized by the Cas-gRNA-DNA complex, allowing them to function as effective copies of natural nucleotides. This copying approach enables enhanced binding affinity through improved structural stability while minimizing immunostimulatory effects because the modifications do not drastically alter the molecular recognition interfaces that would trigger immune responses.
Data Source
AI summary
The present invention relates to modified guide RNAs and their use in clustered, regularly interspaced, short palindromic repeats (CRISPR)/CRISPR-associated (Cas) systems.