Nucleotide sequence of a cDNA encoding an alternative form of LEF-1

Proteins derived from alternatively spliced forms of transcription factor genes have been discovered and shown to be involved in the regulation of their target gene expression. Since alternative forms usually lack one or two functional domains that mediate transcriptional activation, the supressive effect on the function of their normal counterpart is explained by competitive joining to the transcriptional machinery. As for the lymphoid enhancer-binding factor LEF-1, two major transcripts (4.2 and 2.7 kb), which we propose to call LEF-1L and LEF-1S, respectively, have been detected in lymphoid organs as well as pre-B, pre-T, and T cell lines. So far, only the cDNA for LEF-1L has been cloned and analysed. A mouse thymic cDNA library in which insert sizes are restricted between 1.5 and 3.0 kb was screened with a PCR amplified LEF-1L probe (nucleotides 1030-1481 of cDNA clone GN8). One clone we obtained carried a novel 5' part whereas the 3' hybridizing part included the DNA-binding HMG box encoding region. An EcoRI 0.3kb fragment within the novel 5' part detected exclusively the 2.7 kb transcript by Northern blot analysis. Sequence analysis revealed that this clone was 2740bp long (DDBJ, EMBL and GenBank accession number D16503) and that nucleotides 1673-2740 were indentical with the 3' part of LEF-1L, which corresponds to the third and following exons.