We have analysed the expression of the genes encoding transcription factors involved in c-fos transcriptional regulation, i.e. the serum response factor (SRF) and the ETS-related proteins ELK-1 and SAP-1, in a variety of human cell lines. RNA was determined by Northern blot analysis, and proteins were detected on Western blots: the two analyses gave essentially identical results. SRF was expressed at similar levels in all cell lines tested. In contrast, SAP-1 and ELK-1 expression varied from one cell line to another. Interestingly, in any given cell line, high levels of one protein were accompanied by low levels of the other. Similar results were obtained by electromobility shift assays (EMSA), using antibodies directed against the proteins. Thus, our data raise the possibility of a coordinated regulation of the expression of these two Ets genes, at both RNA and protein levels.
