CLONING OF A DNA-BINDING PROTEIN THAT IS A TYROSINE KINASE SUBSTRATE AND RECOGNIZES AN UPSTREAM INITIATOR-LIKE SEQUENCE IN THE PROMOTER OF THE PREPRODYNORPHIN GENE

A 90 bp fragment prepared from the promoter region of the rat preprody norphin gene formed a complex with rat brain nuclear extracts as asses sed by gel mobility shift assays. An 8 base pair sequence, CACTCTCC, t ermed upstream regulatory element (URE), was identified within this fr agment as a binding site by DNase 1 footprint analysis and gel mobilit y shift assays with synthetic oligonucleotides. The URE is a consensus sequence for a transcription initiator (Inr) element although in the preprodynorphin promoter it is located upstream at -208 and overlaps a region conserved between rat and human promoters. A unique 310 amino acid protein (UreB1) that specifically bound the URE was cloned from a rat brain cDNA library using the URE-containing oligonucleotide. Reco mbinantly expressed, affinity purified UreB1 protein retains specific binding to the URE oligonucleotide. UreB1 contains a tyrosine kinase p hosphorylation consensus and binding is enhanced following phosphoryla tion with the p43(v-abl) tyrosine kinase. The UreB1 tyrosine phosphopr otein increases transcription in vitro, consistent with a positive tra nscriptional regulatory function. UreB1 transcripts are well expressed in subsets of neurons in multiple brain areas suggesting that, in add ition to regulation of the preprodynorphin gene, it may have a more ge neralized role in gene transcription.