Thermostable Reverse Transcriptase Bypasses Modified Ribonucleosides
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Solution Overview
Problem
Current methods for reverse transcription of long RNA molecules, particularly those with post-transcriptional modifications, face challenges due to inhibition by modified ribonucleosides, which block or pause reverse transcription, limiting the ability to obtain full-length DNA copies essential for directed evolution and RNA function studies.
Innovation Solution
The use of thermostable reverse transcriptases and bridging primers or extended elongation steps allows the enzyme to bypass or read through modified ribonucleosides, enabling the production of full-length DNA molecules from RNA templates containing post-transcriptional modifications, such as those found in ribosomal RNA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reverse transcriptase is used for RT-PCR of long RNA, then the reaction can proceed under standard conditions, but the modified ribonucleosides block or pause reverse transcription, preventing full-length DNA copy production
Solution Approach 1:
The patent employs a thermostable reverse transcriptase that functions at elevated temperatures (65-95°C) compared to conventional reverse transcriptases that work at 37-50°C. This temperature parameter change allows the enzyme to bypass modified ribonucleosides that block or pause conventional enzymes, enabling full-length DNA copy production from long RNA templates containing post-transcriptional modifications
Solution Approach 2:
The patent introduces bridging primers as intermediary elements that anneal to regions of the RNA template spanning the modified ribonucleosides. These bridging primers serve as mediators that allow the reverse transcriptase to jump over the blocking modifications by providing new starting points for extension, thus enabling complete reverse transcription of long modified RNAs
2Loss of information
If RT-PCR is performed on long RNA templates with modifications, then comprehensive RNA analysis is enabled, but the reaction time must be extended significantly to read through modifications
Solution Approach 1:
By using a thermostable reverse transcriptase that maintains high activity at elevated temperatures, the patent achieves faster elongation rates compared to conventional enzymes. Although extended time is still required for long templates, the thermostable enzyme reduces the total reaction time needed to read through modifications compared to what would be required with conventional reverse transcriptases operating at lower temperatures
3Productivity
If standard RT-PCR conditions are used, then the process is simple and quick, but modified ribonucleosides cause pausing or blocking that limits DNA copy length
Solution Approach 1:
The patent changes the temperature parameter from standard 37-50°C to elevated 65-95°C conditions using a thermostable reverse transcriptase. This parameter change enables the enzyme to maintain high elongation speed while simultaneously being able to traverse modified ribonucleosides, thus achieving both fast reaction kinetics and full-length DNA copy production that would be impossible with conventional enzymes
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 facilitates the recovery of full-length ribosomal RNA, allowing for directed evolution and the identification of post-transcriptional modifications, thereby enhancing the study and engineering of ribosomes and RNA functions.
Implementation Method 1
The conversion of RNA from living cells or in vitro reactions into DNA, a process called reverse-transcription polymerase chain reaction (RT-PCR)
Implementation Method 2
one or more oligonucleotide primers that hybridize to the RNA template
Data Source
AI summary
Disclosed are methods, components, compositions, and kits for preparing DNA molecules by reverse transcribing RNA templates that comprise modified ribonucleosides. The disclosed methods, components, compositions, and kits utilize or comprise thermostable enzymes having RNA-dependent DNA polymerase activity, otherwise referred to as reverse transcriptases.