Identification and characterization of genes upregulated in cells transformed by v-Jun.

The transcription factor Jun (c-Jun) functions as a recipient of extracellular growth signals and converts them into patterns of gene expression. An oncogenic variant of c-Jun was isolated from the acutely transforming retrovirus ASV17. Overexpression of this viral Jun (v-Jun) induces transformation of chicken embryo fibroblasts (CEF) in culture and fibrosarcomas in chickens, v-Jun is a constitutively active form of c-Jun and transforms cells presumably by deregulating the expression of specific target genes. In this report, we describe six genes whose transcripts are upregulated in v-Jun-transformed CEF. Three of these genes show homology to known mammalian genes, to MAP kinase phosphatase 2 (MKP-2), to reversion-induced LIM protein (RIL) and to cytokine-inducible SH2-containing protein (CIS). Northern blot analysis, using CEF infected with various Jun mutants or an estrogen-regulatable Jun chimera, revealed distinct induction patterns of individual targets by v-Jun. The chicken RIL homolog showed an expression pattern tightly correlated with the activity of v-Jun. Its expression is also transformation-dependent, suggesting a role for this gene in v-Jun transformation. The newly identified v-Jun targets can serve as molecular markers in the v-Jun transformation process.