A 2ND PROMOTER AND ENHANCER ELEMENT WITHIN THE IMMUNOGLOBULIN HEAVY-CHAIN LOCUS

The joining of immunoglobulin gene segments during B cell development consists of a tightly regulated series of rearrangement steps. A varie ty of experiments have suggested that transcription is involved in act ivating the locus as substrate for the V(D)J recombinase. Here, we hav e characterized a region located immediately upstream of the most J-pr oximal D element (DQ52),which contains both promoter and enhancer acti vities preferentially active in precursors of B cells. Interestingly, this DQ52 regulatory element is inevitably deleted in fully rearranged H chain genes. We propose that it is involved in the early activation and rearrangement events at the IgH locus.