Shirvani Shervin, Xiang Fan, Koibuchi Nobutaka, Chin Michael T
Vascular Medicine Research, Brigham & Women's Hospital, Harvard Medical School, Cambridge, MA 02139, USA.
Biochem Biophys Res Commun. 2006 Jan 6;339(1):151-6. doi: 10.1016/j.bbrc.2005.10.190. Epub 2005 Nov 9.
The bHLH transcription factor CHF1/Hey2 has been previously shown to regulate neointimal formation after vascular injury, but the mechanisms have not been fully elucidated. The zinc-finger protein GATA-6 has also been shown to regulate vascular smooth-muscle phenotype through regulation of smooth-muscle contractile protein gene expression. To address the potential mechanisms by which CHF1/Hey2 regulates vascular smooth-muscle phenotype switching, we investigated the effect of CHF1/Hey2 on GATA-6-dependent smooth-muscle myosin heavy chain promoter activity. When cotransfected into NIH3T3 cells, CHF1/Hey2 reduced GATA-6-dependent activation of the promoter by 90%. Exogenous p300 was not sufficient to overcome this repression effect, demonstrating that the inhibitor effect did not involve coactivation by p300. Coimmunoprecipitation studies demonstrated that CHF1/Hey2 interacts directly with GATA-6. Mutational analysis demonstrated that the bHLH domain is required for transcriptional repression. Our findings highlight an important transcriptional mechanism by which CHF1/Hey2 may affect smooth-muscle cell phenotype.
bHLH转录因子CHF1/Hey2此前已被证明可调节血管损伤后的新生内膜形成，但其机制尚未完全阐明。锌指蛋白GATA-6也已被证明可通过调节平滑肌收缩蛋白基因表达来调节血管平滑肌表型。为了探究CHF1/Hey2调节血管平滑肌表型转换的潜在机制，我们研究了CHF1/Hey2对GATA-6依赖性平滑肌肌球蛋白重链启动子活性的影响。当共转染到NIH3T3细胞中时，CHF1/Hey2使启动子的GATA-6依赖性激活降低了90%。外源性p300不足以克服这种抑制作用，表明抑制作用不涉及p300的共激活。免疫共沉淀研究表明，CHF1/Hey2直接与GATA-6相互作用。突变分析表明，转录抑制需要bHLH结构域。我们的研究结果突出了CHF1/Hey2可能影响平滑肌细胞表型的重要转录机制。
