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Unstable integration of transfected DNAs into embryonal carcinoma cells
M W McBurney1, S Fournier, P K Schmidt-Kastner
1University of Ottawa, Department of Medicine, Ontario, Canada.
Abstract:
Plasmid DNA can be efficiently transfected into embryonal carcinoma cells but it is difficult to isolate clones of cells stably expressing genes present on the transfected plasmids. Even in clonal populations derived from transfected cells, the introduced genes are expressed in some but not all cells. Cotransfection with a region of the Pgk-1 gene results in more efficient, stable cotransformation due to increased numbers of copies of the transfected plasmids integrated into the genomic DNA. The PgK-1 genomic sequences did not allow the plasmid DNA to replicate autonomously but seemed to enhance the ligation of transfected plasmids before their integration into the host genome. Our results suggest a model in which the plasmid DNAs are able to integrate and subsequently excise from the host genome by recombination events enhanced by transcription through the tandemly repeated sequences of the transfected plasmids.
Insights
Stable gene expression in embryonal carcinoma cells is challenging. Cotransfection with the Pgk-1 gene enhances stable gene integration and expression by promoting plasmid DNA ligation and integration into the host genome.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Efficient gene delivery into embryonal carcinoma cells is achievable via plasmid DNA transfection.
- Stable expression of transfected genes in these cells is difficult to achieve, with variable expression even in clonal populations.
Purpose of the Study:
- To investigate methods for improving stable gene expression in embryonal carcinoma cells.
- To understand the mechanism by which the Pgk-1 gene enhances stable cotransformation.
Main Methods:
- Transfection of plasmid DNA into embryonal carcinoma cells.
- Cotransfection with specific regions of the Pgk-1 gene.
- Analysis of gene integration and expression levels.
Main Results:
- Cotransfection with Pgk-1 gene sequences significantly increased stable cotransformation efficiency.
- Pgk-1 enhanced the integration of multiple plasmid DNA copies into the host genome.
- The Pgk-1 sequences did not facilitate autonomous plasmid replication but promoted ligation and integration.
Conclusions:
- The Pgk-1 gene enhances stable gene transfer by facilitating plasmid DNA integration into the host genome.
- A model involving enhanced recombination, possibly transcription-mediated, explains integration and subsequent excision of plasmid DNA.