Stewart A F, Suzow J, Kubota T, Ueyama T, Chen H H
Department of Medicine, University of Pittsburgh, PA 15213, USA. als6+@pitt.edu
Circ Res. 1998 Jul 13;83(1):43-9. doi: 10.1161/01.res.83.1.43.
Alpha1-adrenergic receptor stimulation induces cardiac myocytes to hypertrophy and reactivates many fetal genes, including beta-myosin heavy chain (betaMyHC) and skeletal alpha-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 alpha1-adrenergic reactivation of the fetal program, expression constructs were cotransfected with betaMyHC and SKA promoter/reporter constructs in neonatal rat cardiac myocytes. TEF-I overexpression tended to transactivate a minimal betaMyHC promoter but significantly interfered with a minimal SKA promoter. In contrast, RTEF-1 transactivated both the minimal betaMyHC and SKA promoters. TEF-1 and RTEF-I also affected the alpha1-adrenergic response of the betaMyHC and SKA promoters differently. TEF-1 had no effect. In contrast, RTEF-1 potentiated the alpha1-adrenergic responses of the SKA promoter and of a -3.3-kb betaMyHC 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 betaMyHC 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 betaMyHC 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 alpha1-adrenergic response in hypertrophic cardiac myocytes.
α1 - 肾上腺素能受体刺激通过肌细胞特异性CAT（M - CAT）顺式元件（转录增强因子 - 1（TEF - 1）家族转录因子的结合位点）发出信号，诱导心肌细胞肥大并重新激活许多胎儿基因，包括β - 肌球蛋白重链（βMyHC）和骨骼肌α - 肌动蛋白（SKA）。为了研究TEF - 1和与TEF - 1相关的RTEF - 1在胎儿程序α1 - 肾上腺素能再激活中的功能差异，将表达构建体与βMyHC和SKA启动子/报告基因构建体共转染到新生大鼠心肌细胞中。TEF - I过表达倾向于反式激活最小的βMyHC启动子，但显著干扰最小的SKA启动子。相反，RTEF - 1反式激活最小的βMyHC和SKA启动子。TEF - 1和RTEF - I对βMyHC和SKA启动子的α1 - 肾上腺素能反应也有不同影响。TEF - 1没有作用。相反，RTEF - 1增强了SKA启动子和 - 3.3 kbβMyHC启动子的α1 - 肾上腺素能反应。为了确定启动子对TEF - 1和RTEF - 1反应不同的原因，以相同方式测试了具有突变M - CAT元件的启动子。βMyHC启动子需要完整的M - CAT元件才能对TEF - 1和RTEF - 1作出反应，而SKA启动子M - CAT是TEF - 1反应所必需的，但不是RTEF - 1反应所必需的，这表明可能涉及SKA启动子特异性辅因子。通过竞争凝胶迁移试验，最小βMyHC启动子的M - CAT亲和力低于SKA启动子，这部分解释了这些启动子对TEF - 1的不同反应。这些结果突出了TEF - 1和RTEF - 1之间的功能差异，并提示RTEF - 1在介导肥厚心肌细胞α1 - 肾上腺素能反应中的新功能。
