TRANSCRIPTIONAL REGULATION OF IMMUNOGLOBULIN GENE-EXPRESSION BY ANTI-IG

When transfected into mouse splenic B cells stimulated with lipopolysa ccharide (LPS) the expression of DNA vectors containing the chloramphe nicol acetyl transferase gene under the control of a SP6 kappa promote r and the lg heavy chain intron enhancer could be down-regulated 5- to 10-fold by treatment of the cells with anti-lg prior to transfection. Exchanging the SP6 kappa promoter by minimal promoters consisting of an octamer or a SP1 motif linked to a TATA box did not impair the anti -lg induced down-regulation while inserting a rabbit beta-globin promo ter did. The transcriptional regulation could be observed after replac ing the lg heavy chain intron enhancer with a SV40 enhancer, or duplic ated minimal Ig heavy chain enhancers containing or lacking the octame r element. The down-regulation was not dependent on the level of trans criptional stimulation observed. A difference in Oct2 expression could neither be detected at the RNA nor protein level after treatment of L PS stimulated B cells with anti-lg or phorbol-dibutyrate. Anti-lg trea tment, but not phorbol-di-butyrate treatment, induced increased levels of AP1 and NF kappa B transcription factors. Thus, either differentia tion specific transcriptional control of lg genes is excerted via tran scription factors common to several distinct enhancers or via transcri ptional adaptor molecules that can interact with several distinct DNA binding proteins.