Mammalian Expression Vector with Flanked Selectable Markers
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Solution Overview
Problem
Robust polypeptide/protein production in mammalian cells remains challenging due to various factors influencing recombinant expression, including promoter strength, post-translational modifications, and gene copy number, despite the advantages of mammalian cells for producing complex therapeutic proteins like monoclonal antibodies.
Innovation Solution
A novel expression vector configuration with specific arrangements of expression cassettes, including a polypeptide of interest (POI) flanked by mammalian selectable and amplifiable selectable marker genes (MSM and MASM), optimized for high-yielding cell line generation, utilizing strong promoters and controlled gene amplification systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If gene amplification is achieved by using cells lines deficient in DHFR or GS with expression vectors containing genes encoding these enzymes and inhibitors like MTX or MSX, then gene copy number increases, but the process becomes complex and time-consuming with multiple selection steps
Solution Approach 1:
The patent combines the selectable marker gene and the gene of interest into a single expression cassette, where both are under the control of the same promoter and regulatory elements. This merging allows simultaneous selection for the marker and amplification of the gene of interest, eliminating the need for separate selection steps and reducing process complexity while achieving high gene copy numbers
Solution Approach 2:
The expression cassette is designed to serve multiple functions: it acts as both a selection marker system and a gene expression system. The selectable marker gene enables cell selection, while the coupled gene of interest is amplified and expressed in the same genetic construct, making the system multi-functional and streamlining the overall process
2Reliability
If multiple expression cassettes are included in the vector for selectable markers and gene of interest, then selection and amplification capabilities are improved, but vector complexity increases
Solution Approach 1:
The patent merges the selectable marker gene and the gene of interest into a single expression cassette with shared regulatory elements. This integration maintains reliable selection and amplification capabilities while significantly reducing vector structure complexity compared to having separate cassettes for each function
Solution Approach 2:
The expression cassette is designed as a multi-functional unit that simultaneously provides selection capability through the marker gene and amplification capability through the coupled gene of interest, both regulated by the same promoter system, thereby reducing the need for multiple separate expression cassettes
3Productivity
If strong promoters are used to drive high-level expression of the polypeptide of interest, then protein production levels increase, but expression of selection markers may also increase unnecessarily
Solution Approach 1:
The patent applies local quality by using different promoter strengths for different genes within the same expression cassette. The gene of interest is under the control of a strong promoter for high-level expression, while the selectable marker gene is under the control of a weaker or constitutive promoter, allowing localized control of expression levels to match functional needs and reduce unnecessary resource consumption
Data Source
AI summary
The invention provides vector nucleic acid for expressing at least one polypeptide of interest in a mammalian cell, comprising(a) at least one expression cassette (POI) for expressing a polypeptide of interest;(b) an expression cassette (MSM) comprising a mammalian selectable marker gene;(c) an expression cassette (MASM) comprising a mammalian amplifiable, selectable marker gene;wherein the expression cassette (POI) is flanked 5′ by the expression cassette (MASM), the expression cassette (MSM) is located 3′ from the expression cassette (POI) and wherein the expression cassettes (MASM), (POI) and (MSM) are arranged in the same 5′ to 3′ orientation.Also provided are host cells, comprising said vector and methods for producing a polypeptide using respective host cells.