A novel NF-kappa B element within exon 1 of the murine c-myc gene.

We have mapped a site within exon 1 of the murine c-myc gene that forms a variety of complexes with nuclear proteins derived from the murine WEHI 231 B-lymphoma cell line in exponential growth that are altered following treatment with phorbol ester, when transcription of this gene is reduced [Levine, R.A., McCormack, J.E., Buckler, A.J. & Sonenshein, G.E. (1986). Mol. Cell Biol., 6, 4112-4116]. This site, located at +440 to +459 bp relative to the P1 promoter, contains an NK-kappa B-like binding element. The sequence of this element, AGGGAATTTTT, is unusual in that the stretch of pyrimidines is entirely T residues. Binding of NF-kappa B protein was demonstrated by oligonucleotide competition, induction of binding upon 70Z/3 pre-B- to B-cell differentiation, response to GTP in the binding reaction, reduction of binding upon addition of I kappa B protein and uv cross-linking analysis. Functional activity of this internal regulatory element (IRE) was demonstrated in transfection assays using chloramphenicol acetyl transferase (CAT) reporter constructs containing multimerized copies of the IRE driving a heterologous promoter. Mutation of the IRE within the context of the c-myc promoter prevented NF-kappa B-mediated induction of transcription of this oncogene. Thus additional NF-kappa B elements may be defined by this new sequence.