In this report, we searched ESEs in the human and murine exon 2 sequence using two ESE-detecting algorithms RESCUE-ESE and ESE finder (35, 43) . Only one ESE, which is a putative binding site for SF2/ASF, was detected by both RESCUE-ESE and ESEfinder 2.0. No ESE was identified in the whole exon 2 when using higher stringent ESEfinder 3.0. Thus, we focused on this ESE for the rest of the experiments.