PRODYNORPHIN GENE-EXPRESSION RELATES TO NF-KAPPA-B FACTORS

The prodynorphin gene contains several kappa B motifs, suggesting that KB-specific DNA-binding factors may regulate its expression. Prodynor phin is known to be expressed in human tumor cell lines [Geijer et al. , Regul. Peptides, 34 (1991) 181-188] and we report here that several DNA-binding factors of the NF-kappa B/c-Rel-family are present in the same cells. Three main kappa B-specific factors, presumably a p50 homo dimer, NF-kappa B which is a p50/p65 heterodimer and a p65/c-Rel heter odimer were identified using an electromobility shift assay (EMSA), im munoabsorption and UV cross-linking experiments. Minor factors consist ing of a novel kappa B-specific protein of about 125 kDa (p125) or bei ng hetero-oligomeric, composed of p125 and either of three other subun its, namely p50, p65 and c-Rel, were also identified. The homo-oligome r of p125 may be identical to the kappa B-specific factor BETA, previo usly found only in brain [Korner et al., Neuron, 3 (1989) 563-572]. Co mparison of prodynorphin mRNA levels with levels of the kappa B-specif ic DNA-binding factors revealed a negative correlation with the level of p50 homodimer, and a positive correlation with the ratio of the lev els of p65/c-Rel to NF-kappa B. No association was found with proenkep halin mRNA levels which were significant in only one eel line. The p50 homodimer, but not p65/c-Rel and NF-kappa B, bound specifically to a DNA-motif within the dynorphin A-encoding gene sequence. This sequence is located in exon 4 and similar to the consensus kappa B-sequence. T he dynorphin A-encoding sequence may represent an intragenic target fo r the p50 homodimer, which when bound to the sequence suppresses trans cription.