The human IL-3 locus is regulated cooperatively by two NFAT-dependent enhancers that have distinct tissue-specific activities
Date
2002
Authors
Hawwari, A.
Burrows, J.
Vadas, M.
Cockerill, P.
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Journal article
Citation
Journal of Immunology, 2002; 169(4):1876-1886
Statement of Responsibility
Hawwari, Abbas ; Burrows, Joanna ; Vadas, Mathew A ; Cockerill, Peter N
Conference Name
Abstract
<jats:title>Abstract</jats:title>
<jats:p>The human IL-3 gene is expressed by activated T cells, mast cells, and eosinophils. We previously identified an enhancer 14 kb upstream of the IL-3 gene, but this element only functioned in a subset of T cells and not in mast cells. To identify additional mechanisms governing IL-3 gene expression, we mapped DNase I hypersensitive (DH) sites and evolutionarily conserved DNA sequences in the IL-3 locus. The most conserved sequence lies 4.5 kb upstream of the IL-3 gene and it encompassed an inducible cyclosporin A-sensitive DH site. A 245-bp fragment spanning this DH site functioned as a cyclosporin A-sensitive enhancer, and was induced by calcium and kinase signaling pathways in both T cells and mast cells via an array of three NFAT sites. The enhancer also encompassed AML1, AP-1, and Sp1 binding sites that potentially mediate function in both T and myeloid lineage cells, but these sites were not required for in vitro enhancer function in T cells. In stably transfected T cells, the −4.5-kb enhancer cooperated with the −14-kb enhancer to activate the IL-3 promoter. Hence, the IL-3 gene is regulated by two enhancers that have distinct but overlapping tissue specificities. We also identified a prominent constitutive DH site at −4.1 kb in T cells, mast cells, and CD34+ myeloid cells. This element lacked in vitro enhancer function, but may have a developmental role because it appears to be the first DH site to exist upstream of the IL-3 gene during hemopoietic development before IL-3 expression.</jats:p>