Modified Alphavirus Replicon RNA Enhances Protein Expression
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Solution Overview
Problem
Current viral expression systems, particularly those using alphaviruses, face limitations in efficiently expressing heterologous proteins, as they often rely on conserved nucleotide sequences that are critical for RNA replication and transcription, making modifications challenging without compromising biological activity.
Innovation Solution
A modified alphavirus replicon RNA with a U->G substitution at position 2 of the 5'-untranslated region (UTR) is developed, which is devoid of substantial portions of the nucleic acid sequence encoding viral structural proteins, enhancing protein expression levels by up to three times compared to wild-type replicons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conserved nucleotide sequences in the 5'-UTR are modified to enhance protein expression, then protein expression levels improve, but RNA replication and transcription efficiency deteriorate
Solution Approach 1:
The patent applies parameter changes by modifying specific nucleotide positions (1, 2, and 4) in the 5'-UTR sequence. The U2G mutation at position 2 and U4G mutation at position 4 alter the biochemical parameters of the RNA structure, enabling enhanced protein expression while preserving RNA replication and transcription functions that would otherwise be compromised by sequence modification
Solution Approach 2:
The invention applies local quality by making targeted mutations at specific positions (1, 2, 4) within the 5'-UTR rather than uniform modifications across the entire sequence. This localized approach allows the conserved regions critical for replication and transcription to remain intact while modifying only the specific nucleotides that enhance protein expression when mutated
2Productivity
If viral structural protein sequences are retained in the replicon, then viral assembly and infectivity are maintained, but expression of heterologous proteins is reduced
Solution Approach 1:
The patent applies the taking out principle by removing or deleting the nucleic acid sequences encoding viral structural proteins from the replicon construct. This extraction of structural protein genes eliminates the competition for translational resources and cellular machinery, thereby enhancing the expression of heterologous proteins while the replicon maintains its essential replication functions through retained non-structural protein sequences
3Productivity
If standard alphavirus replicons are used for protein expression, then system simplicity is maintained, but expression efficiency is limited
Solution Approach 1:
The patent applies parameter changes by introducing specific point mutations (U2G at position 2 and U4G at position 4) in the 5'-UTR of the alphavirus replicon. These parameter changes in the nucleotide sequence dramatically enhance protein expression efficiency (up to three-fold increase) while maintaining the overall simplicity of the replicon structure and avoiding complex modifications to the viral genome architecture
Data Source
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AI summary
The present disclosure generally relates to viral-based expression systems suitable for the production of molecules of interest. The disclosure relates to nucleic acid constructs, such as expression vectors, containing a modified replicon RNA which includes a modified 5 '-unstranslated region (5' -UTR) and, optionally, at least some of its original viral sequence encoding structural proteins having been deleted. Also disclosed are methods for producing polypeptides of interest.