A functional polymorphism in the Eta-1 promoter is associated with allele specific binding to the transcription factor Sp1 and elevated gene expression

Early T lymphocyte activator 1 (Eta- 1), also known as Osteopontin, is a cytokine produced by macrophages and T lymphocytes. It is involved in the regulation of IL- 12 and IL- 10 expression in macrophages and stimulates the polarization of T cells to the Th 1 subset. Three promoter polymorphisms of the human Eta- I gene, -443T/C, - 156delG/G, -66T/G, were investigated for possible influence on gene expression. Electrophoretic mobility shift assays (EMSA) with nuclear extract from the human myeloid leukaemia premonocyte cell line, THP- 1, revealed sequence specific binding of the transcription factor Sp I to the -66T allele but not the -66G allele, and haplotype -443C/- 156G/-66T showed a marked increase in promoter activity of a luciferase reporter gene. Thus, a substitution of the T-base with G at position -66 in the Eta-] promoter modulates the promoter activity of the Eta-] gene, which might influence the Th 1 versus Th 2 balance. These observations are discussed in relation to a recently reported related observation on the same gene, and it is argued that discrepancies between reporter gene assays in the two studies may be due to the use of different cell lines and may reflect requirements for different transcription factors in cells involved in immune responses compared with other cells. (C) 2005 Elsevier Ltd. All rights reserved.