The IRF-2 DNA binding domain facilitates the activation of the class II transactivator (CIITA) type IV promoter by IRF-1.
IFN-gamma induced transcription of class II transactivator (CIITA), a major regulator of MHC class II gene expression, is directed by the CIITA type IV promoter. The IFN-gamma activation of the CIITA type IV promoter is mediated by STAT1 and IRF-1, which bind to the GAS and IRF-E of the promoter, respectively. We and others have determined that IRF-2, another member of the IRF family, also activates the CIITA type IV promoter, by binding to the IRF-E. Also, IRF-2 cooperates with IRF-1 to activate the promoter. DNA binding analyses determined that IRF-1 and IRF-2 can co-occupy the IRF-E of the CIITA type IV promoter. To further understand the mechanism of IRF-1 and IRF-2 cooperativity in the activation of CIITA type IV promoter, we characterized the binding of IRF-1 and IRF-2 to the CIITA IRF-E and mapped the domains of IRF-2 required for the cooperative transactivation. Off-rate experiments revealed that the IRF-2/IRF-E complex was more stable than the IRF-1/IRF-E complex and that the affinity of IRF-1 for the IRF-E was increased when IRF-1 co-occupied the IRF-E with IRF-2. Deletion analysis of functional domains of IRF-2 revealed that a previously described latent activation domain of IRF-2 was essential for IRF-2 transactivation and participated in cooperative activation of the CIITA promoter by IRF-1 and IRF-2. However, the DNA binding domain of IRF-2 was sufficient for cooperativity with IRF-1 in the activation of the CIITA type IV promoter. DNA binding assay demonstrated that, like the full-length IRF-2, the IRF-2 DNA binding domain could co-occupy the CIITA IRF-E with IRF-1.
Xi
Hongkang
H
Department of Biochemistry and Molecular Biology, College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd., Tampa, FL 33612, USA.
Blanck
George
G
D000818:Animals; D001665:Binding Sites; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000235:genetics*; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D007371:Interferon-gamma / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009687:Nuclear Proteins; D010750:Phosphoproteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors
D004268:DNA-Binding Proteins; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; C494258:Irf1 protein, mouse; C494230:Irf2 protein, mouse; C083728:MHC class II transactivator protein; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D007371:Interferon-gamma; D004247:DNA