Reference - Detail
|Author||Takeda N, Arima M, Tsuruoka N, Okada S, Hatano M, Sakamoto A, Kohno Y, Tokuhisa T.|
|Title||Bcl6 is a transcriptional repressor for the IL-18 gene.|
Bcl6 functions as a sequence-specific transcriptional repressor, and Bcl6-deficient (Bcl6(-/-)) mice have been reported to display Th2-type inflammatory diseases in multiple organs. Since IL-18 is a potent stimulator of Th2 cells, we examined the expression of IL-18 mRNA in bone marrow-derived macrophages from Bcl6(-/-) mice after LPS stimulation. Here we show that the expression was strikingly up-regulated after stimulation. The expression was also up-regulated in RAW264 cells, a murine macrophage cell line, by transfection with the dominant negative type of Bcl6 gene. We identified a putative Bcl6-binding DNA sequence (IL-18BS) upstream of exon 1 of the murine IL-18 gene and three IL-18BSs in the promoter region of human IL-18 gene. Binding of Bcl6 in nuclear protein from resting RAW264 cells to murine IL-18BS was detected by gel retardation assay and chromatin immunoprecipitation assay. The binding activity was diminished gradually in RAW264 cells after LPS stimulation. However, the amount of Bcl6 protein in these cells was constant over the period examined, suggesting the functional modification of Bcl6 protein after stimulation. Furthermore, murine IL-18BS was required for Bcl6 to repress the expression of the luciferase reporter gene under control of the IL-18 promoter. Taken together, Bcl6 is a key regulator of IL-18 production by macrophages.
|MeSH||Animals Base Sequence Binding Sites / genetics Bone Marrow Cells / immunology Bone Marrow Cells / metabolism Cell Line Cells, Cultured DNA-Binding Proteins / deficiency DNA-Binding Proteins / genetics DNA-Binding Proteins / metabolism DNA-Binding Proteins / physiology* Down-Regulation / genetics Down-Regulation / immunology* Gene Expression Regulation / immunology Gene Silencing / immunology* Humans Interleukin-18 / antagonists & inhibitors* Interleukin-18 / biosynthesis Interleukin-18 / genetics* Lipopolysaccharides / pharmacology Macrophage Activation / genetics Macrophage Activation / immunology Macrophages / immunology Macrophages / metabolism Mice Mice, Inbred C57BL Mice, Knockout Promoter Regions, Genetic / immunology Proto-Oncogene Proteins / deficiency Proto-Oncogene Proteins / genetics Proto-Oncogene Proteins / metabolism Proto-Oncogene Proteins / physiology* Proto-Oncogene Proteins c-bcl-6 RNA, Messenger / biosynthesis Repressor Proteins / genetics Repressor Proteins / metabolism Repressor Proteins / physiology* Transcription Factors / deficiency Transcription Factors / genetics Transcription Factors / metabolism Transcription Factors / physiology* Transfection Up-Regulation|
|Human and Animal Cells|