EXPRESSION OF 2 MYELOID CELL-SPECIFIC GENES REQUIRES THE NOVEL TRANSCRIPTION FACTOR, C-FES EXPRESSION FACTOR

The protein product of the c-fes proto-oncogene has been implicated in the normal development of myeloid cells (macrophages and granulocytes ). We have previously shown that 151 base pairs of c-fes 5'-flanking s equences are sufficient for myeloid cell-specific expression and inclu de functional binding sites for Spl, PU.1, and a novel nuclear factor (Heydemann, A., Juang, G., Hennessy, K., Parmacek, M. S., and Simon, M . C. (1996) Mol, Cell Biol, 16, 1676-1686), This novel hematopoietic t ranscription factor, termed FEF (c-fes expression factor), binds to a cis-acting element that is located at nucleotides -9 to -4 of the c-fe s promoter between two Ets binding sites (at -19 to -15 and -4 to +1) which bind PU.1. We now show that a FEF binding site exists in the mye loid cell-specific regulatory region of a second gene, the -2.7-kiloba se pair enhancer of chicken lysozyme. The lysozyme FEF site is immedia tely 5' to a PU.1 site, analogous to their arrangement in the c-fes pr omoter, and allows the formation of a preliminary FEF consensus site, 5'-GAAT(C/G)A-3'. This consensus site does not match any sites for kno wn transcription factors. Importantly, although PU.1 binds immediately 3' of the FEF site in both the c-fes promoter and the chicken lysozym e enhancer (CLE), we show that they bind independently, The FEF sites are required for high levels of transcription by both the CLE and the c-fes promoter in transient transfection experiments, Importantly, eli mination of the CLE FEF site abolishes all transcriptional activity of this enhancer element, Mutation of the adjacent PU.1 site in either t he c-fes promoter or the CLE, reduces activity by approximately 50%. T herefore, transcription of both lysozyme and fee in myeloid cells requ ires FEF and PU.1. UV cross-linking experiments show that the FEF bind ing activity consists of a single 70-kDa protein in both human and mur ine cell lines, FEF binding activity is not affected by antibodies tha t specifically recognize a number of cloned transcription factors, Col lectively, these data indicate that we have identified a novel transcr iption factor that is functionally important for the expression of at least two myeloid cell-specific genes.