GATA- and Smad1-dependent enhancers in the Smad7 gene differentially interpret bone morphogenetic protein concentrations
GATA- and Smad1-dependent enhancers in the Smad7 gene differentially interpret bone morphogenetic protein concentrations
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DOI：
10.1128/mcb.23.18.6646-6661.2003
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发表时间：
2003-09-01
影响因子：
5.3
通讯作者：
Wrana, JL
中科院分区：
文献类型：
--
作者：
Benchabane, H;Wrana, JL
Smad7是一种转化生长因子β超家族信号的抑制剂，在抑制反馈回路中由骨形态发生蛋白（BMP）诱导。在这里，我们鉴定了Smad7基因中的多个BMP应答元件（BREs），并证明它们以细胞类型特异性的方式不同地解释BMP信号。两个bre （bre1和bre2）位于启动子区域。其中一个包含几个保守的Smad1和Smad4结合位点，它们协同介导bmp依赖性诱导，很可能是在缺乏DNA结合伙伴的情况下。第三个BRE （I-BRE）位于第一个内含子中，包含GATA因子结合位点。GATA-1、-5或-6是I-BRE强激活所必需的，我们发现它们在活细胞中与Smad1在I-BRE上组装。I-BRE的激活是由GATA-5和-6中的特定区域介导的，但不需要与Smad1直接的物理相互作用。I-BRE与BRE-1的比较表明，I-BRE对低BMP浓度的反应更强。此外，染色质免疫沉淀实验分析表明，内源性I-BRE被内源性Smad1比BRE-1更强烈地占据。这与Smad7基因的调控有关，在表达gata的细胞系中，与不表达gata的细胞系相比，BMP浓度较低时，Smad7基因被诱导表达。因此，这些数据定义了合作和非合作smad依赖的转录调控如何解释不同的BMP浓度。
Smad7, an inhibitor of transforming growth factor beta superfamily signaling, is induced by bone morphogenetic protein (BMP) in an inhibitory feedback loop. Here, we identify multiple BMP response elements (BREs) in the Smad7 gene and demonstrate that they function differentially to interpret BMP signals in a cell type-specific manner. Two BREs (BRE-1 and -2) reside in the promoter region. One of these contains several conserved Smad1 and Smad4 binding sites that cooperate to mediate BMP-dependent induction, most likely in the absence of DNA binding partners. The third BRE (I-BRE) resides in the first intron and contains GATA factor binding sites. GATA-1, -5, or -6 is required for strong activation of I-BRE, and we show that they assemble with Smad1 on the I-BRE in living cells. Activation of the I-BRE is mediated by a specific region in GATA-5 and -6 but does not require direct physical interaction with Smad1. Comparison of I-BRE to BRE-1 showed that I-BRE is more responsive to low BMP concentrations. Moreover, analysis by chromatin immunoprecipitation experiments demonstrates that the endogenous I-BRE is occupied more robustly by endogenous Smad1 than is BRE-1. This correlates with regulation of the Smad7 gene, which is induced at lower BMP concentrations in GATA-expressing cell lines compared to non-GATA-expressing lines. These data thus define how cooperative and noncooperative Smad-dependent transcriptional regulation can function to interpret different BMP concentrations.