We have analysed differential gene expression in v-jun-transformed chicken embryo fibroblasts (CEF) compared to normal CEF by using the directional tag PCR subtraction method. From a first generation of putative Jun targets four clones were selected for study; they are upregulated in jun-transformed cells. Three of these clones showed homology to known genes: glutaredoxin, growth associated protein (GAP)-43/neuromodulin, and phenobarbital-induced cytochrome P450. The expression of these genes was analysed in fibroblasts transformed by various oncogenes. Expression of the glutaredoxin mRNA could be induced by a Jun-estrogen receptor chimaera in the absence of de novo protein biosynthesis. Based on this observation we conclude that glutaredoxin is a direct target of v-Jun.