We tested sequences flanking the mouse c-fos gene for the ability to form specific DNA-protein complexes with factors present in crude nuclear extracts prepared from mammalian cells. Three such complexes were detected. One complex formed in a region necessary for the induction of c-fos expression by serum growth factors. Two additional complexes formed at sequences that contribute to basal c-fos promoter activity in vivo. These complexes represent three novel sequence-specific DNA-binding activities which appear to participate in the regulation of c-fos transcription.
