CRISPR Cleavage Product Capture With Specific 5′ Overhangs
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Solution Overview
Problem
Current methods for capturing nucleic acids cleaved by endonucleases, such as dA-tailing, are inefficient and non-specific, leading to unwanted ligation of both desired and undesired nucleic acids.
Innovation Solution
A method involving controlled exonuclease digestion to generate a 5'-overhang in nucleic acids, allowing for specific ligation with adaptors having complementary 5'-overhangs, thereby enhancing capture efficiency and specificity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dA-tailing method is used to capture nucleic acids, then the capture process is simple, but the capture specificity is low and unwanted nucleic acids are also ligated
Solution Approach 1:
The invention creates locally different end structures on nucleic acid fragments - specifically generating 5' overhangs with defined sequences through controlled exonuclease digestion. This local structural differentiation allows specific adaptors to bind only to their complementary targets, resolving the contradiction between simple processing and high specificity by making the ligation site locally unique rather than uniformly simple.
Solution Approach 2:
The invention changes the physical-chemical parameters of nucleic acid ends by controlling exonuclease digestion to generate specific 5' overhang lengths and sequences. By adjusting digestion conditions (enzyme type, temperature, time, buffer composition), the method achieves both simplicity of operation and high capture specificity through parameter optimization.
2Speed
If dA-tailing is used to add overhangs, then ligation is kinetically advantaged, but the method is nonspecific and all nucleic acids with accessible 3'-end are modified
Solution Approach 1:
The invention performs preliminary action by pre-generating specific 5' overhangs on target nucleic acids through controlled exonuclease digestion before ligation. This preliminary structuring ensures that only the intended targets possess the correct overhang configuration, so when adaptors are added, ligation occurs rapidly and specifically only at the pre-prepared sites, not at all accessible ends.
Solution Approach 2:
The invention introduces controlled exonuclease digestion as an intermediary step between nucleic acid preparation and ligation. This intermediary process acts as a selective gatekeeper that converts diverse nucleic acid ends into uniform, specific 5' overhangs, mediating between the starting material and the ligation reaction to ensure both speed and specificity.
3Productivity
If cohesive end ligation is used, then ligation efficiency is improved, but an unwanted inserted nucleotide is added to coding sequences
Solution Approach 1:
The invention employs asymmetric overhang structures where the 5' overhang on the nucleic acid fragment is designed to be complementary to a specific sequence on the adaptor, rather than using symmetric blunt ends or universal dA-dT overhangs. This asymmetry ensures directional, sequence-specific ligation that maintains reading frame accuracy in coding sequences while achieving high ligation efficiency through cohesive end pairing.
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
The method achieves more efficient and specific capture of target nucleic acids, reducing unwanted ligation products and improving downstream analysis such as sequencing.
Implementation Method 1
contacting a double-stranded target nucleic acid having a 3'-end with a catalyst possessing 3'-5'-exonuclease activity thereby generating a first 5'-overhang at a first 5'-end and a first recessed 3'-end
Implementation Method 2
contacting the nucleic acid with an adaptor having a second 5'-overhang at a second 5'-end, the second 5'-overhang capable of hybridizing to the first 5'-overhang thereby forming a hybrid between the first and second 5'-overhangs
Implementation Method 3
linking at least one of the first 3'-end with the second 5'-end thereby capturing the target nucleic acid by forming an adapted nucleic acid
Data Source
AI summary
The invention is a method of capturing DNA ends formed by endonuclease cleavage, such as CRISPR endonuclease cleavage, for downstream analysis including amplification and sequencing.