A complex composed of USF1 and USF2 activates the human FcεRI α chain expression via a CAGCTG element in the first intron

The high-affinity IgE receptor, FcεRI, is a key regulatory molecule in the allergic reaction. During the course of studies to find cis-acting elements for FcεRI α chain gene expression, a CAGCTG sequence located in the first intron was revealed to serve as a crucial enhancer element. Electromobility shift assays using antibodies and in vitro translation products showed that the CAGCTG element was recognized by the USF1/USF2 complex. As was the case for other intronic cis-elements, the CAGCTG element regulated the promoter in an orientation- and position-dependent manner. Overexpression of USF2 antisense repressed the FcεRI α chain gene promoter and decreased the amount of α chain mRNA in mast cell lines. All these results indicated that the USF1/USF2 complex activates the human FcεRI α chain gene expression via the CAGCTG element in the first intron.