GATA2 and Sp1 positively regulate the c-kit promoter in mast cells

The c-kit gene is expressed in hematopoietic stem cells and lineage progenitor cells but is downregulated during cell development in most lineages, except for mast cells. In mast cells, high expression of c-kit is maintained during development, and c-Kit signaling is essential for mast cell development. To analyze the mechanisms by which c-kit gene expression are regulated in mast cells, we examined mast cell type-specific regulation of the c-kit promoter region. We observed that a GC-box in the c-kit promoter was critical for transcriptional activity and was bound to the transcription factor Sp1 as assessed using reporter assay and electrophoretic mobility assay. Chromatin immunoprecipitation assay and coexpression analyses showed that the transcription factor GATA2, which was recruited to the c-kit promoter in a mast cell-specific manner, in addition to Sp1, transactivated the c-kit promoter via the GC-box. Electrophoretic mobility assay and rechromatin immunoprecipitation assay indicated that GATA2 binds to the GC-box by forming a complex with Sp1. Introduction of Sp1 small interfering RNA significantly reduced the amount not only of Sp1 but also of GATA2 binding to the c-kit promoter in mast cells, resulting in suppression of c-kit transcription. Knockdown of GATA2 suppressed the recruitment of GATA2 toward the c-kit promoter, subsequently suppressing cell surface expression of c-Kit. These findings indicate that GATA2 and Sp1 play crucial roles in expression of the c-kit gene in mast cells.