Modified T7 RNA Polymerase for High-Yield 2'-O-Methylated Transcript Production
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Solution Overview
Problem
The incorporation of fully 2'-O-methylated nucleotides during the SELEX process is hindered by low transcription yields, which affects the stability and efficacy of aptamer therapeutics.
Innovation Solution
Modified T7 RNA polymerases, such as those with altered amino acids at positions 639, 784, and 378, are used to increase the transcriptional yield of 2'-O-methylated nucleotides by reducing discrimination against 2'-Ome nucleotide triphosphates, allowing for higher incorporation rates in transcription reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wild-type T7 RNA polymerase is used for transcription, then the enzyme maintains high fidelity and natural substrate specificity, but the transcription yield of 2'-O-methylated nucleotides is low due to discrimination against modified nucleotide triphosphates
Solution Approach 1:
The patent applies parameter changes by mutating specific amino acid residues in the T7 RNA polymerase active site (positions 639, 784, and 378) to alter the enzyme's substrate specificity. These parameter changes in the enzyme's structure enable it to accept modified nucleotide substrates (2'-O-methylated NTPs) that were previously discriminated against, thereby resolving the contradiction between maintaining fidelity and improving productivity with modified substrates.
Solution Approach 2:
The mutated T7 RNA polymerase acts as an intermediary that bridges the gap between the natural enzyme and the modified nucleotide substrates. By introducing specific mutations, the polymerase creates an intermediate state where it can accommodate the bulkier 2'-O-methyl groups while still maintaining catalytic function, thus enabling high-yield transcription of fully modified transcripts.
2Stability of the object's composition
If fully 2'-O-methylated nucleotides are incorporated during SELEX, then aptamer stability and therapeutic effectiveness are improved, but transcription yield decreases due to enzyme discrimination
Solution Approach 1:
The patent resolves this contradiction by changing the parameters of the T7 RNA polymerase through site-directed mutagenesis. The mutations at positions 639 (Y to L), 784 (H to A), and 378 (K to R) collectively alter the enzyme's active site properties, enabling it to efficiently transcribe templates containing fully 2'-O-methylated nucleotides without sacrificing transcription yield, thus allowing high-stability aptamers to be produced at sufficient quantities.
3Reliability
If modified nucleotide triphosphates are used as substrates, then the resulting transcripts have enhanced nuclease resistance and therapeutic properties, but the incorporation rate is reduced due to steric hindrance at the 2'-position
Solution Approach 1:
The patent applies local quality by making specific localized changes to the polymerase active site architecture. The mutations at positions 639, 784, and 378 create local structural modifications in the substrate binding region that specifically accommodate the 2'-O-methyl group geometry. This localized adaptation allows the enzyme to process modified substrates at rates comparable to unmodified substrates while maintaining the nuclease resistance benefits of full 2'-O-methylation.
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 modified polymerases enhance the yield of fully 2'-O-methylated transcripts, improving the stability and production efficiency of aptamers, thereby prolonging their in vivo stability and therapeutic effectiveness.
Implementation Method 1
the skilled person knows how to identify, make and use such a molecule in the absence of a precise structural definition
Implementation Method 2
Modified T7 RNA polymerases, such as those with altered amino acids at positions 639, 784, and 378, are used to increase the transcriptional yield of 2'-O-methylated nucleotides
Data Source
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AI summary
Materials and methods are provided for producing aptamer therapeutics having fully modified nucleotide triphosphates incorporated into their sequence.