Cooperation between core binding factor and adjacent promoter elements contributes to the tissue-specific expression of interleukin-3.
Tissue-specific expression of interleukin-3 (IL-3) is mediated via cis-acting elements located within 315 base pairs of the transcription start. This is achieved in part through the positive activities of the AP-1 and Elf-1 sites in the IL-3 promoter. The contribution to T cell-specific expression by other promoter sites was assessed in a transient expression assay with IL-3 promoter constructs linked to a luciferase gene, focusing initially on the core binding factor (CBF) site, which is footprinted in vivo upon T cell activation. Activity of the CBF site is shown to be critically dependent on the adjacent activator site Act-1. Together the Act-1 and CBF sites form a functional unit (AC unit) with dual activity. The AC unit is demonstrated to enhance basal activity of promoters both in fibroblasts and T cells. This activity is further inducible in activated T cells, but not in fibroblasts. In addition to the already identified NIP repressor site, evidence is presented for a second repressor region that restricts promoter activity in fibroblasts. Finally, a novel positive regulatory element has been mapped in the IL-3 promoter between nucleotide -180 and -210 that leads to increased expression in T cells. Together these results demonstrate that T cell expression of IL-3 is not specified by the activity of a single tissue-specific element, but instead involves multiple interacting elements that provide both specific positive regulation in T cells and specific negative regulation in fibroblasts.
Taylor
D S
DS
Divisions of Pediatric Hematology and Oncology, Dana Farber Cancer Institute, Boston, Massachusetts 02115, USA.
Laubach
J P
JP
Nathan
D G
DG
Mathey-Prevot
B
B
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007377:Interleukin-3 / Q000096:biosynthesis* / Q000235:genetics*; D008156:Luciferases / Q000096:biosynthesis; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D009928:Organ Specificity; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000096:biosynthesis; D012045:Regulatory Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D016385:TATA Box; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection
D004268:DNA-Binding Proteins; C512897:ELF1 protein, human; C512896:Elf1 protein, mouse; D007377:Interleukin-3; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D008156:Luciferases