Response of Djun and Dfos mRNA abundance to signal transduction pathways in cultured cells of Drosophila melanogaster

The mammalian proto-oncogenes c-jun and c-fos are situated at the end of mu ltiple signal transduction pathways and activation of their products Jun an d Fos, components of the transcription factor AP-1, are able to regulate ge ne transcription in response to extracellular stimuli. Djun and Dfos, the p roducts of the Drosophila proto-oncongenes Djun and Dfos, are similar in si ze and sequence to their mammalian counterparts c-Jun and c-Fos and are rel ated to their mammalian counterparts by their antigenic properties. However , very little is known about how they are regulated through signal transduc tion pathways. This paper has investigated the response of their mRNA abund ance levels to three signal transduction pathways in Drosophila cultured ce lls. Various agonists and anagonists that stimulate and inhibit specific en zymes in the pathways have been tested. The results suggest that Djun and D fos mRNA are continuously expressed and their abundance levels are transien tly regulated by multiple signaling pathways, the peak response coming at 1 -2 hours after perturbation. Dfos is more highly regulated than Djun which is only modulated. The receptor tyrosine kinase pathways positively regulat e Dfos and Djun. The cAMP-mediated pathway positively regulates Dfos but ne gatively regulates Djun. The protein kinase C-activated pathway does not af fect Djun whereas it negatively regulates Dfos.