IDENTIFICATION AND FUNCTIONAL-CHARACTERIZATION OF A HIGHLY CONSERVED SEQUENCE IN THE INTRON OF THE KAPPA-LIGHT-CHAIN GENE

A highly conserved 225 bp sequence was identified within the J-C intro n of the murine kappa light-chain immunoglobulin gene and its nuclear protein-binding and regulatory function were examined. The binding of nuclear proteins to this fragment was found to reflect the differentia tion state of the cell used to prepare the nuclear extracts and three different complexes are seen with this fragment: CI, CII and CIII. CII I is present in all cell types. CI is present in fibroblasts, T cells and early B cells, but not mature B cells. Moreover, nuclear extracts prepared from the early pre-B cell line, 70Z/3, that was treated with agents which activate kappa gene transcription have a reduced ability to form CI. Therefore, the presence of CI correlates with the absence of kappa gene transcription. CII is present in all stages of B cell de velopment, however its composition changes with B cell maturation. Con tained within the 225 bp element is the ets family-binding motif GGAA and the B-cell-and-macrophage-specific family member, PU.1 binds this sequence and participates in CII formation. The 225 bp fragment showed modest augmentation of expression in CAT reporter constructs containi ng the heavy chain enhancer (HCE) and a light chain promoter in the pl asmacytoma, S194, and uninduced 70Z/3 cells and mediated a small but r eproducible response to IFN-gamma in 70Z/3 cells. Thus, the 225 bp seq uence contained within the J-C intron may function as a regulatory ele ment for kappa light chain gene expression. Copyright (C) 1996 Elsevie r Science Ltd