Identification and expression analysis of alternative transcripts of the mouse GA-binding protein (Gabp) subunits alpha and beta1.

The erythroblast transformation specific (ETS) transcription factor GA-binding protein (Gabp) is widely expressed and acts on a diverse range of target genes, including nuclear-encoded mitochondrial proteins and neuromuscular-specific genes. The GABPalpha subunit contains an ETS DNA binding domain and the beta subunit contains a nuclear localization signal (NLS) and transactivation domain. Here, we show coincident expression of Gabpalpha and beta1 throughout mouse embryogenesis, consistent with the gene products functioning in a complex. We have also identified 2 alternatively spliced, tissue-specific exons 1 (5' untranslated regions) of mouse Gabpalpha and 4 alternative 3' polyadenylation signals that, in combination, result in 12 transcripts for Gabpalpha. These alternative transcripts are suggested to have altered stability, subcellular localization and/or translation efficiency. Further, we identified nine differentially expressed splice variants of mouse Gabpbeta1 that encode beta protein forms lacking functional domains, suggesting a dominant negative function. Together, alternative transcripts of Gabpalpha and beta1 provide a mechanism for tissue-specific regulation of Gabp activity.