IDENTIFICATION OF A TISSUE-SPECIFIC AND DIFFERENTIATION STAGE-SPECIFIC ENHANCER OF THE VPREB1 GENE

The VpreB and lambda 5 genes encode proteins that associate non-covale ntly to form the so-called surrogate light (SL) chain. The SL chain co mplexes with the immunoglobulin heavy chain to form the pre-B cell rec eptor, which plays a critical role in B cell development. Expression o f the murine SL genes is regulated at the level of transcription initi ation. Here, we show that a VpreB1 enhancer is located within the 356 bp immediately upstream of the coding sequence. Interestingly, this re gion exhibits 96 % identity to the upstream region of VpreB2. Deletion mapping located the enhancer to between positions -214 and -47 (+ 1 i s the 5'-most transcription initiation site). The enhancer is tissue a nd differentiation stage specific, and is composed of several DNA elem ents that are important for its activity. We also show that a transcri ption factor, early B cell factor, binds to two such elements, and tha t at least one of these sites is involved in determining enhancer acti vity.