Characterization of the human and mouse ETV1/ER81 transcription factor genes: role of the two alternatively spliced isoforms in the human

The Ets transcription factors of the PEA3 group-E1AF/PEA3, ETV1/ER81 and ER M-are almost identical in the ETS DNA-binding and the transcriptional acidi c domains. To accelerate our understanding of the molecular basis of putati ve diseases linked to ETV1 such as Ewing's sarcoma we characterized the hum an ETV1 and the mouse ER81 genes. We showed that these genes are both encod ed by 13 exons in more than 90 kbp genomic DNA, and that the classical acce ptor and donor splicing sites are present in each junction except for the 5 ' donor site of intron 9 where GT is replaced by TT. The genomic organizati on of the ETS and acidic domains in the human ETV1 and mouse ER81 (localize d to chromosome 12) genes is similar to that observed in human ERM and huma n E1AF/PEA3 genes. Moreover, as in human ERM and human E1AF/PEA3 genes, a f irst untranslated exon is upstream from the first methionine, and the mouse ER81 gene transcription is regulated by a 1.8 kbp of genomic DNA upstream from this exon. In human, the alternative splicing of the ETV1 gene leads t o the presence (ETV1 alpha) or the absence (ETV1 beta) of exon 5 encoding t he C-terminal part of the transcriptional acidic domain, but without affect ing the alpha helix previously described as crucial for transactivation. We demonstrated here that the truncated isoform (human ETV1 beta) and the ful l-length isoform (human ETV1 alpha) bind similarly specific DNA Ets binding sites. Moreover, they both activate transcription similarly through the PK A-transduction pathway, so suggesting that this alternative splicing is not crucial for the function of this protein as a transcription factor. The co mparison of human ETV1 A and human ETV1 beta expression in the same tissues , such as the adrenal gland or the bladder, showed no clear-cut differences . Altogether, these data open a new avenue of investigation leading to a be tter understanding of the functional role of this transcription factor.