title: Investigation of factors responsible for cell line cytoplasmic expression differences.
abstract: BACKGROUND
  Previous work has described a novel cytoplasmic expression system that results in a 20-fold increase in the levels of gene expression over a standard CMV-based nuclear expression system, as compared with a 2-3 fold increase seen with previous similar systems. While this increase was seen with BHK and Neuro-2a cells, further studies revealed that some cell lines, such as COS-7, demonstrated relatively poor levels of cytoplasmic expression. The objective of this study was to determine what factors were responsible for the different expression levels between BHK (a high expressing cell line) and COS-7 (a low expressing cell line).
  
  
  RESULTS
  The main findings of this work are that the individual elements of the cytoplasmic expression system (such as the T7 RNAP gene and Internal Ribosome Entry Sequence) are functioning similarly in both cell types. Both cell types were found to have the same amount of cytosolic nuclease activity, and that the cells appeared to have differences in the intra-cellular processing of DNA-cationic lipid complexes.
  
  
  CONCLUSIONS
  After exploring many factors, it was found that differences in the intra-cellular processing of the DNA-cationic lipid complex was the most probable factor responsible for the difference in cytoplasmic gene expression.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, B.C., Canada. jdfinn@interchange.ubc.ca
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Finn
authors.forename: Tabitha
authors.initials: T
authors.lastname: Wong
authors.forename: Pieter R
authors.initials: PR
authors.lastname: Cullis
mesh_terms: D000818:Animals; D019556:COS Cells / Q000378:metabolism*; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism*; D003851:Deoxyribonucleases / Q000032:analysis; D004686:Encephalomyocarditis virus / Q000235:genetics; D015870:Gene Expression / Q000235:genetics / Q000502:physiology*; D010957:Plasmids / Q000235:genetics; D012323:RNA Processing, Post-Transcriptional / Q000502:physiology; D014162:Transfection
chemical_list: D003851:Deoxyribonucleases