[LEU(5)]ENKEPHALIN-ENCODING SEQUENCES ARE TARGETS FOR A SPECIFIC DNA-BINDING FACTOR

A DNA-binding factor with high affinity and specificity for the [Leu(5 )]enkephalin-encoding sequences in the prodynorphin and proenkephalin genes has been characterized, The factor has the highest affinity for the [Leu(5)]enkephalin-encoding sequence in the dynorphin B-encoding r egion of the prodynorphin gene, has relatively high affinity for other [Leu(5)]enkephalin-encoding sequences in the prodynorphin and proenke phalin genes, but has no apparent affinity for similar DNA sequences c oding for [Met(5)]enkephalin in the prodynorphin or proopiomelanocorti n genes, The factor has been named [Leu(5)] enkephalin-encoding sequen ce DNA-binding factor (LEF), LEF has a nuclear localization and is com posed of three subunits of about 60, 70, and 95 kDa, respectively, The highest levels were observed in rat testis, cerebellum, and spleen an d were generally higher in late embryonal compared to newborn or adult animals, LEF activity was also recorded in human clonal tumor cell li nes, LEF inhibited the transcription of reporter genes in artificial g ene constructs where a [Leu(5)]enkephalin-encoding DNA fragment had be en inserted between the transcription initiation site and the coding r egion of the reporter genes. These observations suggest that the [Leu( 5)]enkephalin-encoding sequences in the prodynorphin and proenkephalin genes also have regulatory functions realized through interaction wit h a specific DNA-binding factor.