Assembly of a functional beta interferon enhanceosome is dependent on ATF-2-c-jun heterodimer orientation.
Heterodimeric transcription factors, including the basic region-leucine zipper (bZIP) protein ATF-2-c-jun, are well-characterized components of an enhanceosome that mediates virus induction of the human beta interferon (IFN-beta) gene. Here we report that within the IFN-beta enhanceosome the ATF-2-c-jun heterodimer binds in a specific orientation, which is required for assembly of a complex between ATF-2-c-jun and interferon regulatory factor 3 (IRF-3). We demonstrate that correct orientation of the ATF-2-c-jun binding site is required for virus induction of the IFN-beta gene and for IRF-3-dependent activation of a composite ATF-2- c-jun-IRF site in the IFN-beta promoter. We also show that in vitro the DNA-bound ATF-2-c-jun heterodimer adopts a fixed orientation upon the binding of IRF-3 at an adjacent site in the IFN-beta enhancer and that the DNA-binding domain of IRF-3 is sufficient to mediate this effect. In addition, we show that the DNA-binding domain of ATF-2 is necessary and sufficient for selective protein-protein interactions with IRF-3. Strikingly, in vivo chromatin immunoprecipitation experiments with IFN-beta reporter constructs reveal that recruitment of IRF-3 to the IFN-beta promoter upon virus infection is dependent on the orientation of the ATF-2-c-jun heterodimer binding site. These observations demonstrate functional and physical cooperativity between the bZIP and IRF transcription factor families and illustrate the critical role of heterodimeric transcription factors in formation of the IFN-beta enhanceosome.
Falvo
J V
JV
Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
Parekh
B S
BS
Lin
C H
CH
Fraenkel
E
E
Maniatis
T
T
D051698:Activating Transcription Factor 2; D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D003432:Cross-Linking Reagents; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D019281:Dimerization; D004742:Enhancer Elements, Genetic; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells / Q000821:virology; D006801:Humans; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D050838:Interferon Regulatory Factor-3; D016899:Interferon-beta / Q000235:genetics* / Q000378:metabolism*; D016350:Leucine Zippers; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010750:Phosphoproteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins; D020218:Response Elements; D014157:Transcription Factors / Q000378:metabolism*
C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; D003432:Cross-Linking Reagents; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; C494257:IRF1 protein, human; C494229:IRF2 protein, human; C494232:IRF3 protein, human; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D050838:Interferon Regulatory Factor-3; D010750:Phosphoproteins; D016755:Proto-Oncogene Proteins c-jun; D011994:Recombinant Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D016899:Interferon-beta; D004247:DNA; D005982:Glutathione Transferase