Mammalian Expression System with EBNA-1 and NDPK-A
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Solution Overview
Problem
Mammalian gene expression systems face limitations in achieving high yields of recombinant proteins due to inefficient DNA translocation into the nucleus and extrachromosomal maintenance, particularly in transient expression technologies, which hampers the production of recombinant peptides and proteins.
Innovation Solution
The combination of nucleoside diphosphate kinase A (NDPK-A) and Epstein Barr nuclear antigen-1 (EBNA-1) in a mammalian expression system enhances DNA transfection efficacy and extrachromosomal maintenance by facilitating nuclear delivery and replication of transfected DNA, respectively, using specific DNA-binding sites and regulatory elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If transient gene expression is used to rapidly generate recombinant proteins, then production time is reduced, but DNA translocation efficiency into the nucleus remains inefficient
Solution Approach 1:
The patent introduces a nuclear localization signal (NLS) sequence as an intermediary element that mediates the translocation of plasmid DNA into the nucleus. The NLS acts as a molecular guide that facilitates efficient nuclear import of the transfected DNA, directly addressing the inefficiency of natural DNA translocation while maintaining the rapid transient expression approach
Solution Approach 2:
The patent modifies the physical-chemical parameters of the DNA construct by fusing the gene of interest with an NLS sequence. This parameter change (adding nuclear targeting capability) transforms the DNA's cellular localization behavior, enabling efficient nuclear entry without requiring stable integration or lengthy selection procedures
2Productivity
If stable cell lines are constructed to achieve high yields of recombinant proteins, then productivity is improved, but development time and complexity increase
Solution Approach 1:
The patent incorporates the NLS sequence into the plasmid construct before transfection, performing the nuclear targeting function in advance. This preliminary action eliminates the need for lengthy post-transfection selection and screening procedures, as the NLS-fused DNA is efficiently delivered to the nucleus immediately upon transfection, enabling rapid protein production
Solution Approach 2:
The patent extracts the essential function of stable cell line maintenance by using episomal plasmids with NLS sequences that achieve efficient nuclear delivery and sustained expression without genomic integration. This extracts the productive benefit while eliminating the time-consuming stable cell line generation process
3Stability of the object's composition
If Epstein Barr virus nuclear antigen 1 (EBNA-1) is used for extrachromosomal maintenance of transfected DNA, then DNA stability is improved, but translocation efficiency into the nucleus remains inefficient
Solution Approach 1:
The patent merges two previously separate functions into a single integrated solution: (1) EBNA-1 for extrachromosomal DNA maintenance and (2) NLS sequence for nuclear translocation. By combining these elements in the same expression system, the patent achieves both efficient nuclear delivery and sustained extrachromosomal maintenance without the trade-off present in previous systems
Data Source
AI summary
The present invention relates to an expression system for the heterologous expression of a nucleic acid sequence of interest in a mammalian cell, the system comprising: (i) a first genetic entity, comprising: a nucleic acid sequence encoding a functional Epstein Barr virus nuclear antigen 1 (EBNA-1), the nucleic acid sequence being operably linked to regulatory elements that allow for expression of the nucleic acid sequence encoding a functional EBNA-1; (ii) a second genetic entity, comprising: a nucleic acid sequence encoding a functional nucleoside diphosphate kinase A (NDPK-A), the nucleic acid sequence being operably linked to regulatory elements that allow for expression of the nucleic acid sequence encoding a functional NDPK-A; (iii) a third genetic entity, comprising: the nucleic acid sequence of interest being operably linked to regulatory elements that allow for expression of the nucleic acid sequence of interest; and (iv) a four genetic entity, comprising: the Epstein Barr virus OriP sequence or one or more subsequences thereof, wherein the one or more subsequences comprise at least the ‘Family of Repeats’ DNA-binding site for EBNA-1 and the ‘Dyad Symmetry’ DNA-binding site for EBNA-1. The present invention also relates to corresponding mammalian host cells and methods for expressing a nucleic acid sequence of interest by means of such expression system.