Mapping of epidermal growth factor-, serum-, and phorbol ester-responsive sequence elements in the c-jun promoter

Abstract

Expression of the nuclear proto-oncogene c-jun is rapidly and transiently induced by many growth factors, serum, and tumor promoters. The sequence elements in the c-jun promoter involved in serum or growth factor induction have not been identified. The c-jun promoter region between -117 and -72 contains binding sites for the transcription factors Sp1, CTF, and AP-1. An additional sequence element has been noted at position -59. This A+T-rich sequence, formerly proposed as a TFIID-binding site, conforms to the consensus binding sequence of a recently identified factor, RSRF (related to serum response factor). In this study, we mapped the sequences in the c-jun promoter responsible for epidermal growth factor (EGF), serum, and 12-O-tetradecanoylphorbol-13-acetate (TPA) induction by deletion and point mutational analysis. We found that the c-jun RSRF site is an important element for EGF and serum induction of the promoter and that there are several factors in HeLa nuclear extracts which specifically bind to this site. The RSRF site was also sufficient for EGF, serum, and TPA induction when assayed on a heterologous promoter. The c-jun AP-1 site was not required for EGF, serum, or TPA induction but was sufficient to mediate a weak response to these agents when assayed on a heterologous promoter. Double mutation of the RSRF and AP-1 sites suggests that there is an additional TPA-responsive element between -80 and +150 in the c-jun promoter.