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, Fc epsilon RI, is a key regulatory molecule in the allergic reaction. During the course of studies to find cis-acting elements for Fc epsilon RI alpha 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 Fc epsilon RI alpha chain gene promoter and decreased the amount of alpha chain mRNA in mast cell lines. All these results indicated that the USF1/USF2 complex activates the human Fc epsilon RI alpha chain gene expression via the CAGCTG element in the first intron.