Transcriptional regulation of galectin-10 (eosinophil Charcot-Leyden crystal protein): a GC box (-44 to -50) controls butyric acid induction of gene expression.

Galectin-10 (gal-10, also known as Charcot-Leyden crystal protein) is a member of the galectin family of beta-galactoside binding proteins that is expressed uniquely in eosinophilic and basophilic leukocytes. To gain a better understanding of galectin gene expression, we present an analysis of the transcriptional regulation of the gene encoding gal-10. Analysis of the minimal promoter revealed nine consensus-binding sites for transcription factors, including several that are also found in the minimal promoters of galectins -1, -2, and -3. The decrease in gal-10 promoter activity after disruption of either the GC box (-44 to -50) or the Oct site (-255 to -261) suggests that these sites, along with the previously characterized GATA and EoTF sites, are necessary for full promoter activity. By supershift analysis, we demonstrate binding of the transcription factors Sp1 and Oct1 to the consensus GC box and the Oct site, respectively. Similar to gal-1, gal-10 expression is induced by butyric acid, an effect that is lost upon ablation of the GC box. Additionally, we demonstrate AML3 binding to the consensus AML site and YY1 binding to the Inr sequence, both elements functioning as silencers in the gal-10 promoter.