Repression of AP-1-stimulated transcription by c-Ets-1.

The transcriptional activities of c-Ets-1 and v-Ets and their functional interaction with the AP-1 factor c-Jun were investigated. Several recombinant Ets proteins were produced and purified either from bacteria or from insect cells. Plasmid DNAs that contained the polyoma virus enhancer Ets/AP-1 element were used as templates for in vitro transcription assays in the presence of HeLa nuclear extract and various combinations of the Jun and Ets proteins. Under these conditions full-length c-Ets-1 on its own does not markedly influence transcription but abolishes the strong transcriptional stimulation normally elicited by Jun. This repression depends on the Ets-binding site and on specific features of c-Ets-1 structure, as both v-Ets and a natural splicing variant c-Ets-1 (delta VII) fail to inhibit Jun activity. These findings suggest that c-Ets may act both as a transcriptional repressor or activator depending on promoter context and splicing pattern.