The tet-off system is more effective than the tet-on system for regulating transgene expression in a single adenovirus vector.
BACKGROUND
Control of transgene expression in mammalian cells is desirable for gene therapy and the study of gene function in basic research. This study evaluates the functionality of single adenovirus (Ad) vectors containing a tetracycline-controllable expression system (tet-off or tet-on system).


METHODS
An Ad-mediated binary transgene expression system was generated containing a tet-off or a tet-on system, which introduced the gene of interest with a tetracycline-regulatable promoter and the tetracycline-responsive transcriptional activator gene into the E1 and E3 deletion regions, respectively. The functionality of the Ad-mediated tet-off and tet-on systems was compared under various conditions in vitro and in vivo.


RESULTS
The Ad vector containing the tet-off system provided negative control of gene expression ranging from 20- to 500-fold, depending on the cell type and condition. In contrast, the Ad vector containing the tet-on system increased gene expression by only 2- to 28-fold and required about two-log orders higher concentration of an inducer (doxycycline) to switch on the gene expression, compared with the Ad vector containing the tet-off system.


CONCLUSIONS
Ad vectors containing the tet-off system are a better choice for regulated gene expression than Ad vectors containing the tet-on system. Single Ad vectors containing the tetracycline-controllable expression system will greatly facilitate in vitro and in vivo analyses of gene function and may be useful for gene therapy.
Mizuguchi
Hiroyuki
H
Division of Biological Chemistry and Biologicals, National Institute of Health Sciences, Tokyo 158-8501, Japan. mizuguch@nihs.go.jp
Hayakawa
Takao
T
D000256:Adenoviridae / Q000235:genetics*; D002460:Cell Line; D004797:Enzyme-Linked Immunosorbent Assay; D015967:Gene Expression Regulation, Viral / Q000502:physiology*; D005822:Genetic Vectors; D006801:Humans; D010957:Plasmids; D012097:Repressor Proteins / Q000502:physiology*; D015534:Trans-Activators / Q000502:physiology*; D014161:Transduction, Genetic; D019076:Transgenes
D012097:Repressor Proteins; D015534:Trans-Activators; C034811:tetracycline resistance-encoding transposon repressor protein