Suppressive effect of Elf-1 on FcεRI α-chain expression in primary mast cells

The high-affinity receptor for immunoglobulin E (IgE), FcεRI, is specifically expressed in mast cells and basophils and plays a key role in IgE-mediated allergic reactions. The transcription factor Elf-1 has been previously identified to bind to the promoter of the human FcεRI α-chain, which is essential for the function and expression of FcεRI. In the present study, Elf-1 siRNA was conducted to evaluate the effects of Elf-1 on FcεRI α-chain expression in the primary mouse mast cells, bone marrow-derived mast cells (BMMC). Introduction of Elf-1 siRNA effectively reduced expression levels of Elf-1 mRNA and protein in BMMC. Transient reporter assay showed that the knockdown of Elf-1 by siRNA resulted in increased FcεRI α-chain promoter activity, while overexpression of Elf-1 suppressed α-chain promoter activity in BMMC. Elf-1 siRNA-treated BMMC exhibited marked upregulation of FcεRI α-chain transcription, whereas β-chain mRNA was not affected by Elf-1 siRNA. Chromatin immunoprecipitation assay showed that the amount of transcription factor PU.1, recognizing the cis-element close to the Elf-1-site on the FcεRI α-chain promoter, was significantly increased by introduction of Elf-1 siRNA. These results indicate that Elf-1 negatively regulates FcεRI α-chain expression by suppressing PU.1-mediated transcription of the α-chain in BMMC.