Identification of a putative human ig h chain 3′ enhancer

A lymphuid-specific transcriptional enhancer element has been identified at the distant 3′ end of the mouse and rat Ig heavy chain (IgH) locus. Analysis of these enhancer sequences, has revealed distinct evolutionary conservation between the two species. In the mouse and the rat, the IgH 3′ enhancer consists of a core region flanked by inverted repeats. The overall sequence identity in the overlapping areas is 62%. We have identified a 487bp segment of the putative human IgH 3′ enhancer (3′E_H) possibly homologous to the mouse 3′ E_H core region. Human gonomic DNA was subjected to PCR amplification using primers designed on the basis of mouse core sequences (sense primer: position 618-610: antisense primer: position 1156-1179). Amplified DNA was cloned into pCR II vector and scquenced by dideoxy chain termination. Sequence alignment with the mouse 618-1179 amplicon showed 48% identity using the Lipmann-Pearson DNA Identity Search method. Subsequence search for known transcription factor binding motifs, with one mismatch allowed, showed the following (# of sites) : ortamor (1), AP1 (3), AP2 (1), AP4 (2), SV40 general enhancer core (7), muE1 (1), muE2 (2), muE3 (1), muE5 (5). Thus, the isolated human 487bp sequence may display lymphoid-specific transcriptional regulatory function similar to that of its mouse counterpart. Ongoing studies are aimed at the definition of the whole human IgH 3′E sequence, and at the functional characterization of this element in enhancer assays involving different human B cell lines.