Regulation of the human FcεRI α-chain distal promoter

The α-chain of the high affinity receptor for IgE (FcεRI) is essential for cell surface expression of FcεRI and binding of the IgE Ab. The human α-chain gene possesses two promoters: the proximal promoter, which is highly conserved with that of rodent; and the distal promoter, the structure and role of which are largely unknown. Transcriptional regulation of the α-chain distal promoter was investigated in this study. Transient reporter assay revealed critical region for transcription activity located within -27/-17. EMSA identified Elf-1, YY1, and PU.1 as transcription factors binding to this region. In contrast to the proximal promoter, which was trans-activated by YY1 and PU.1, these transcription factors exhibited repressive function on this promoter. Addition of IL-4 caused a marked increase in transcription from the distal promoter and subsequently increased the intracellular production of the α-chain. These results indicate that IL-4-dependent up-regulation of the human α-chain was due to enhancement of distal promoter activity and suggests that the two promoters have different regulatory mechanisms for α-chain expression.