SILENCING OF THE EXPRESSION OF THE IMMUNOGLOBULIN KAPPA-GENE IN NON-B CELLS

Although the activating factor NF-kappa-B can be present in the nucleus of many cell types, transcription and rearrangement of the immunoglobulin kappa chain gene is restricted to cells of the B lineage. Part of this specificity is determined by sequences within the major intron of the kappa gene that specifically silence gene expression in non-B cells (T cells and HeLa cells). These sequences are found in a 232-bp fragment located 5' of the NF-kappa-B binding sequence of the enhancer. When this fragment is added back upstream of an active NF-kappa-B site, it specifically decreases the expression of a linked gene by more than 10-fold in activated T cells but it has no effect on expression in B cells. The kappa silencer region acts in an orientation- and distance-independent manner and appears to be composed of multiple negative elements. The kappa silencer may act to restrict transcription and rearrangement of the C-kappa locus to cells of the B lineage.