POSSIBLE STAGE-SPECIFIC FUNCTION OF NF-KAPPA-B DURING PRE-B-CELL DIFFERENTIATION

Lipopolysaccharide (LPS)-induced differentiation of the murine pre-B c ell line 70Z/3 is a model for pre-B to B cell differentiation and has been used to show that the transcription factor NF-kappa B is essentia l to induce the expression of the Ig kappa gene. We have investigated the mechanism involved in late stages of the process when all cells ha ve reached a more mature B phenotype, i.e, beyond 48 up to 96 h of LPS treatment. NF-kappa B binding activity was induced at early times by LPS treatment, but its DNA binding activity disappeared after 83 h of LPS treatment. Accumulation of I kappa B alpha protein in the nucleus correlated with the disappearance of NF-kappa B activity at 72, 84 and 96 h, and treatment of nuclear extracts of 72-96 h LPS-treated cells with Na-deoxycholate restored NF-kappa B binding activity. The data in dicate that NF-kappa B, wile important to initiate the process of Ig k appa gene transcription in 70Z/3 pre-B cells, is no longer required fo r its maintenance in differentiated 70Z/3 cells. (C) 1998 Federation o f European Biochemical Societies.