Identification of a transcriptional enhancer element upstream from the proto-oncogene fos

Sequences upstream from the proto-oncogene fos were shown to be essential for its transcription. Transient expression of the chloramphenicol acetyl-transferase (CAT) gene linked to upstream sequences of the fos gene including its promoter reveals that sequences located 64 to 404 base pairs 5' to the fos cap site contain a typical transcriptional enhancer. Moreover, these enhancer sequences, which are strikingly conserved between mouse and human fos genes, coincide with a deoxyribonuclease I-hypersensitive site in the chromatin. The expression of the fos-CAT fusion genes was stimulated only two to three times by the fos inducer 12-0-tetradecanoyl phorbol-13-acetate. The fos enhancer does not appear to be tissue-specific.