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Fos and Jun oncogenes transactivate chimeric or native promoters containing AP1/GCN4 binding sites in plant cells
P Hilson1, D de Froidmont, C Lejour
1Station d'Amélioration des Plantes, Gembloux, Belgium.
Abstract:
The function of mammalian transcription factors of the leucine zipper class was investigated in leaf-derived protoplasts of tobacco. In transient expression experiments, Fos and Jun strongly activated chimeric promoters composed of the TATA box region of the cauliflower mosaic virus 35S transcript preceded by one to five copies of an AP1/GCN4 binding site. Fos and Jun also stimulated a wheat high molecular weight glutenin promoter in which similar binding sites are located more than 500 base pairs from its transcription start site. Both the DNA binding and the transcription activation domains of these proteins were required for proper promoter stimulation by Fos and Jun. Each factor alone was partially active, suggesting that at least the Fos protein can associate with an endogenous plant transcription factor. These observations support the hypothesis that sequences related to AP1/GCN4 binding sites could be cis-acting modules involved in the transcriptional regulation of plant genes.
Insights
Mammalian Fos and Jun proteins activate plant gene promoters by binding to specific DNA sequences. This suggests conserved mechanisms for transcriptional regulation across species.
Area of Science:
- Molecular Biology
- Plant Science
- Genetics
Background:
- Transcription factors regulate gene expression by binding to specific DNA sequences.
- Leucine zipper proteins are a class of transcription factors found in mammals.
- Understanding cross-species gene regulation can reveal conserved biological mechanisms.
Purpose of the Study:
- To investigate the function of mammalian leucine zipper transcription factors (Fos and Jun) in plant systems.
- To determine if these factors can regulate gene expression in tobacco leaf protoplasts.
- To identify potential conserved cis-acting regulatory elements in plant genes.
Main Methods:
- Transient expression experiments were conducted in tobacco leaf protoplasts.
- Chimeric promoters containing cauliflower mosaic virus 35S TATA box and AP1/GCN4 binding sites were used.
- A wheat high molecular weight glutenin promoter was also tested.
- The roles of DNA binding and transcription activation domains of Fos and Jun were assessed.
Main Results:
- Fos and Jun strongly activated chimeric promoters with AP1/GCN4 binding sites.
- These factors also stimulated a wheat glutenin promoter with similar binding sites.
- Both DNA binding and transcription activation domains were essential for promoter stimulation.
- Partial activity of individual factors suggested interaction with endogenous plant factors.
Conclusions:
- Mammalian Fos and Jun can function as transcriptional activators in plant cells.
- AP1/GCN4-like binding sites may act as cis-acting regulatory modules in plant gene transcription.
- Conserved mechanisms for transcriptional regulation involving leucine zipper proteins might exist between mammals and plants.