Two-Plasmid Mammalian Expression System for RDRP Virus Rescue
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Solution Overview
Problem
Current methods for reconstituting RNA-dependent RNA polymerase (RDRP) enzyme activity for recombinant protein and virus production require multiple plasmids, making the process complex and inefficient, especially for negative-stranded RNA viruses like Measles and Rinderpest, which limits the scope of RDRP-based systems for large-scale protein expression and virus rescue.
Innovation Solution
A two-plasmid mammalian expression system is developed, where one plasmid expresses the N, P, and L proteins of Measles virus, and another plasmid provides an easily manipulatable RNA substrate, allowing for the reconstitution of RDRP enzyme activity for protein expression and virus rescue, eliminating the need for external T7 RNA polymerase and simplifying the transfection process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple plasmids are used to reconstitute RDRP enzyme activity, then the system can produce recombinant proteins and viruses, but the process becomes complex and inefficient
Solution Approach 1:
The patent combines multiple plasmid functions into a single plasmid that expresses both the viral RNA genome and the RDRP enzyme components (N, P, and L proteins). This merging eliminates the need for co-transfecting multiple separate plasmids, thereby reducing system complexity while maintaining the ability to reconstitute RDRP enzyme activity and produce recombinant proteins and viruses.
Solution Approach 2:
The invented plasmid system is designed to be universally applicable for producing various recombinant proteins and viruses. The single plasmid contains modular elements including viral promoter sequences, multiple open reading frames for N, P, and L proteins, and RNA polymerase recognition sites, allowing it to function as a versatile expression system for different viral targets without requiring plasmid-specific optimizations.
2Ease of operation
If external T7 RNA polymerase is required for the expression system, then transcription can be initiated, but the system becomes more complex and less self-sufficient
Solution Approach 1:
The patent creates a self-sufficient expression system where the plasmid itself encodes all necessary components for RNA transcription. The L protein expressed from the plasmid serves as the RNA-dependent RNA polymerase, eliminating the need for external T7 RNA polymerase or other host-derived polymerases. This self-service capability simplifies the system by making it autonomous.
Solution Approach 2:
The plasmid design includes specific promoter sequences and RNA polymerase recognition sites that serve as intermediaries between the genetic information and the transcription process. These built-in regulatory elements mediate the initiation of transcription by the viral RDRP enzyme encoded within the same plasmid, creating a self-contained transcriptional system.
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 enhances the efficiency of RDRP enzyme reconstitution and expands its application for large-scale recombinant protein expression and virus production, facilitating the development of recombinant modified viruses for therapeutic and vaccine purposes.
Implementation Method 1
viral RNA dependent RNA polymerase (RDRP) initiates transcription of genomic RNA from its promoter present within the leader sequence and produces messenger ribonucleic acid (mRNA) molecules
Implementation Method 2
the RDRP enzyme switches mode and initiates replication from another promoter present within the leader sequence of the genomic RNA
Data Source
Figure 1~1C
Figure 2
Figure 3a~3B
AI summary
Reverse engineering has offered new ways of studying the pathobiology of RNA viral infections, new more efficient means of synthesizing recombinant viruses and developing vaccines and also demonstrated the versatility and efficiency of RNA dependent RNA polymerase RDRP system as an expression system. However, the currently used methods require a repertoire of complex, difficult-to- use tools. Present invention describes, a simpler plasmid based mammalian expression system that uses the RDRP enzyme activity for expression of recombinant proteins or RNA from viral minigenomes and rescue of recombinant viruses from cDNAs encoding entire genome(s) of negative stranded RNA viruses. This system will be useful for expression of recombinant proteins, therapeutic RNA molecules including anti-sense and/or selective interefering RNA and Ribozymes. This system can also be used for gene therapy and producing recombinant viruses for production of new vaccines.