Molecular cloning of rat USF2 cDNA and characterization of splicing variants

The complete nucleotide sequence of rat USF2 cDNA was determined. In addition to the full length clone (USF2FL), four isoforms (Δ1, Δ2, Δ3, and Δ4) suggested to be generated by alternative splicing were isolated. USF2Δ1 and Δ2 lacked 27 and 67 internal amino acid residues, respectively, USF2Δ3 and Δ4 lacked most of the entire sequence but encoded short peptides of an N-terminal portion of USF2FL. Overexpression of USF2FL increased the transcription of the human high affinity IgE receptor (FcεRI) α chain gene through specific binding to the CAGCTG motif in the first intron. On the other hand, overexpression of USF2Δ1 or Δ2 reduced the transcription of the human FcεRI α chain gene. Both USF2FL and USF2Δ1 bound to CACGTG as well as CAGCTG, while USF2Δ2 bound to CACGTG but not to CAGCTG. These results suggested the presence of a different and definitive role of each variant in the expression of the a chain gene.