B lymphocyte-induced maturation protein (Blimp)-1, IFN regulatory factor (IRF)-1, and IRF-2 can bind to the same regulatory sites.
The transcriptional repressor B lymphocyte-induced maturation protein-1 (Blimp-1) is expressed in some differentiated cells and is required for terminal differentiation of B cells. To facilitate identification of Blimp-1 target genes, we have determined the optimal DNA recognition sequence for Blimp-1. The consensus is very similar to a subset of sites recognized by IFN regulatory factors (IRFs) that contain the sequence GAAAG. By binding competition and determination of equilibrium dissociation constants, we show that Blimp-1, IRF-1, and IRF-2 have similar binding affinities for functionally important regulatory sites containing this sequence. However, Blimp-1 does not bind to all IRF sites, and specifically does not recognize IRF-4/PU.1 or IRF-8 sites lacking the GAAAG sequence. Chromatin immunoprecipitation studies showed that Blimp-1, IRF-1, and IRF-2 all bind the IFN-beta promoter in vivo, as predicted by the in vitro binding parameters, and in cotransfections Blimp-1 inhibits IRF-1-dependent activation of the IFN-beta promoter. Thus, our data suggest that Blimp-1 competes in vivo with a subset of IRF proteins and help predict the sites and IRF family members that may be affected.
Kuo
Tracy C
TC
Department of Microbiology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
Calame
Kathryn L
KL
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics / Q000276:immunology; D001667:Binding, Competitive / Q000235:genetics / Q000276:immunology; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D016899:Interferon-beta / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D010750:Phosphoproteins / Q000378:metabolism*; D000074462:Positive Regulatory Domain I-Binding Factor 1; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000378:metabolism*; D017422:Sequence Analysis, DNA / Q000379:methods; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection
D004268:DNA-Binding Proteins; C494257:IRF1 protein, human; C494229:IRF2 protein, human; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; C494258:Irf1 protein, mouse; C494230:Irf2 protein, mouse; D010750:Phosphoproteins; C513258:Prdm1 protein, mouse; D012097:Repressor Proteins; D014157:Transcription Factors; C087042:PRDM1 protein, human; D016899:Interferon-beta; D000074462:Positive Regulatory Domain I-Binding Factor 1