Intergenic Elements Enhance Gene Expression in Mammalian Host Cells
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for selecting mammalian cells with high expression levels of bioactive proteins face challenges due to low selection stringency, leading to low expression levels of the protein of interest, as the selection marker proteins often require only small amounts to neutralize toxic agents, resulting in insufficient mRNA and protein production.
Innovation Solution
Incorporating specific nucleic acid constructs, such as those with sequences from the retinoblastoma 1 (Rb1) and Cyclin-dependent kinase 4 inhibitor B (CDKN2B) genomic regions, upstream of an expression cassette, to enhance intergenic transcription and chromatin openness, thereby increasing mRNA and protein production levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a selectable marker gene is coupled to the gene of interest to enable selection of transfected cells, then cell selection capability is improved, but the selection stringency remains low because the selection marker protein requires only small amounts to neutralize toxic agents, resulting in low expression levels of both the selection marker and the gene product of interest
Solution Approach 1:
The patent divides the selection system into two functionally independent components: (1) a selectable marker gene that provides binary selection capability (survival/death), and (2) an intergenic element that independently enhances transcriptional activity. This segmentation allows the selection marker to operate at low expression levels for reliable selection while the intergenic element boosts expression of the gene of interest without being constrained by the selection threshold, thereby resolving the contradiction between selection reliability and productivity
Solution Approach 2:
The intergenic element acts as a mediator between the promoter and the gene of interest, enhancing transcriptional activity without interfering with the selection mechanism. By placing this intermediary element upstream of the gene of interest, the system achieves higher expression levels of the gene product while maintaining the original selection stringency, thus resolving the contradiction between selection capability and expression productivity
2Reliability
If multiple copies of the plasmid are incorporated to increase expression levels of the selection marker, then selection stringency is improved, but the number of gene copies for the gene of interest remains limited, resulting in low transgenic protein expression levels
Solution Approach 1:
The patent separates the functions of selection and expression enhancement into distinct genetic elements. The selectable marker provides selection stringency through its binary survival/death mechanism, while the intergenic element independently amplifies transcriptional output. This allows the system to achieve high selection stringency with single-copy integration while the intergenic element boosts expression levels without requiring multiple plasmid copies, resolving the contradiction between selection stringency and gene copy number
Solution Approach 2:
The intergenic element changes the transcriptional parameter of the system by enhancing RNA polymerase recruitment or elongation efficiency. This parameter change allows single-copy integrants to achieve expression levels equivalent to or exceeding multiple-copy systems, while maintaining the selection stringency provided by the selectable marker, thus resolving the contradiction between selection stringency and quantity of gene copies
Data Source
AI summary
The present invention relates to nucleic acid fragments and constructs comprising genomic nucleotide sequences, which are present upstream of Rb1 and p15C that are associated with intergenic transcription, for the production of a gene product of interest in a eukaryotic, preferably mammalian, host cell in the presence of a stringent selectable marker. The invention further relates to host cells comprising the nucleic acid constructs, to methods for generating the host cells and to methods for producing a gene product of interest using the host cells.