Molecular cloning of rat USF2 cDNA and characterization of splicing variants

The complete nucleotide sequence of rat USF2 cDNA was determined. In additi on to the full length clone (USF2FL), four isoforms (Delta1, Delta2, Delta3 , and Delta4) suggested to be generated by alternative splicing were isolat ed. USF2 Delta1 and Delta2 lacked 27 and 67 internal amino acid residues, r espectively, USF2 Delta3 and Delta4 lacked most of the entire sequence but encoded short peptides of an N-terminal portion of USF2FL. Overexpression o f USF2FL increased the transcription of the human high affinity IgE recepto r (Fc epsilon RI) alpha chain gene through specific binding to the CAGCTG m otif in the first intron. On the other hand, overexpression of USF2 Delta1 or Delta2 reduced the transcription of the human Fc epsilon RI alpha chain gene. Both USF2FL and USF2 Delta1 bound to CACGTG as well as CAGCTG, while USF2 Delta2 bound to CACGTG but not to CAGCTG. These results suggested the presence of a different and definitive role of each variant in the expressi on of the alpha chain gene.