| We have investigated the mechanism for how BCL 6 represses Blimp 1 transcription , and have found that BCL 6 regulates the Blimp 1 promoter through a novel mechanism involving AP 1 elements . ^^^ Specifically , BCL 6 is a potent repressor of transcriptional activity mediated by AP 1 factors . ^^^ An estrogen receptor ligand binding domain fusion with the BCL 6 zinc finger domain can act as a estrogen inducible dominant negative protein and increase AP 1 activity in BCL 6 ( + ) cells but not in BCL 6 ( ) cells , indicating that endogenous BCL 6 represses AP 1 activity . ^^^ Repression of AP 1 function by BCL 6 may be a key mechanism for how BCL 6 regulates gene expression to control inflammation , lymphocyte differentiation , and lymphomagenesis . . ^^^ We found that the zinc finger region of BCL 6 interacts with c Jun , JunB , and JunD proteins but does not bind c Fos or Fra 2 proteins . ^^^ |