Transcription Factor RTEF-1 Mediates a1-Adrenergic Reactivation of the Fetal Gene Program in Cardiac Myocytes

a1-Adrenergic receptor stimulation induces cardiac myocytes to hypertrophy and reactivates many fetal genes, including b-myosin heavy chain (bMyHC) and skeletal a-actin (SKA), by signaling through myocyte-specific CAT (M-CAT) cis elements, binding sites of the transcriptional enhancer factor-1 (TEF-1) family of transcription factors. To examine functional differences between TEF-1 and related to TEF-1 (RTEF-1) in a1-adrenergic reactivation of the fetal program, expression constructs were cotransfected with bMyHC and SKA promoter/reporter constructs in neonatal rat cardiac myocytes. TEF-1 overexpression tended to transactivate a minimal bMyHC promoter but significantly interfered with a minimal SKA promoter. In contrast, RTEF-1 transactivated both the minimal bMyHC and SKA promoters. TEF-1 and RTEF-1 also affected the a1-adrenergic response of the bMyHC and SKA promoters differently. TEF-1 had no effect. In contrast, RTEF-1 potentiated the a1-adrenergic responses of the SKA promoter and of a 23.3-kb bMyHC promoter. To determine why the promoters responded differently to TEF-1 and RTEF-1, promoters with mutated M-CAT elements were tested in the same way. The bMyHC promoter required an intact M-CAT element to respond to TEF-1 and RTEF-1, whereas the SKA promoter M-CAT was required for the TEF-1 response but not for the RTEF-1 response, suggesting that SKA promoter–specific cofactors may be involved. By competition gel shift assay, the M-CAT of the minimal bMyHC promoter had a lower affinity than that of the SKA promoter, which partly explains the different responses of these promoters to TEF-1. These results highlight functional differences between TEF-1 and RTEF-1 and suggest a novel function of RTEF-1 in mediating the a1-adrenergic response in hypertrophic cardiac myocytes. (Circ Res. 1998;83:43-49.)