THE PLANT CELL, Vol 2, Issue 7 651-658, Copyright © 1990 by American Society of Plant Biologists
Fos and Jun Oncogenes Transactivate Chimeric or Native Promoters Containing AP1/GCN4 Binding Sites in Plant Cells
P. Hilson, D. de Froidmont, C. Lejour, S. I. Hirai, J. M. Jacquemin and M. Yaniv
Station d'Amelioration des Plantes, 4 rue du Bordia, 5800 Gembloux, Belgium
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.