Sp1 binds to the G allele of the-1087 polymorphism in the IL-10 promoter and promotes IL-10 mRNA transcription and protein production.

Interleukin (IL)-10 is an important cytokine in immune regulation and promotes B-cell proliferation and antibody production. High levels of IL-10 were found in subjects with autoimmune diseases. The A to G single nucleotide polymorphism at -1087 of the IL-10 promoter is associated with differences in promoter activity and IL-10 production. The objectives of this study were to analyze differences in the transcription factor binding to the -1087 IL-10 gene polymorphism in B-cells, the influence of the A to G transition on the IL-10 and Sp1 gene expression in B-cells after lipopolysaccharide (LPS) stimulation and the effect of knockdown of Sp1 on IL-10 gene expression. Using B-cell lines obtained from subjects with GG and AA genotypes for the -1087 polymorphism and chromatin immunoprecipitation assay, we showed that the transcription factors PU.1 and Spi-B bound to both G and A alleles, whereas the transcription factor Sp1 only bound to the G allele. LPS stimulation of the B-cells resulted in a larger increase in IL-10 and Sp1 gene expression for GG genotypes than AA genotypes and knockdown of Sp1 gene expression resulted in a decrease in IL-10 mRNA transcription. IL-10 production was higher for the GG genotype than for the AA genotype.