The E<lambda>3-1 Enhancer is Essential for V(D)J Recombination of the Murine Immunoglobulin Lambda Light Chain Locus

Enhancers are essential for long range chromatin opening and the activation of V(D)J recombination at the antigen receptor loci. The murine immunoglobulin lambda light chain locus is a duplicated locus and, using a bacterial artificial chromosome spanning the 3′ half of the locus to generate transgenic mice, we have identified a critical enhancer element for lambda locus recombination. Four hypersensitive sites had been previously mapped downstream of the JCλ1 gene segment (HS1-4). Systematic deletion of these individual hypersensitive sites showed that HS1, which forms the major part of the transcription enhancer, Eλ3–1, is essential for Igλ recombination and that it also helps to restrict Igλ stage-specific recombination.