Transcriptional repression by the basic helix-loop-helix protein Dec2: multiple mechanisms through E-box elements.
Transcriptional repression by the basic helix-loop-helix protein Dec2: multiple mechanisms through E-box elements.
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DOI：
10.3892/ijmm.19.6.925
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发表时间：
2007-06
影响因子：
5.4
通讯作者：
K. Fujimoto;Hidenori Hamaguchi;Takafumi Hashiba;Tadahiro Nakamura;T. Kawamoto;F. Sato;M. Noshiro;U. Bhawal;Ketut Suardita;Y. Kato
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文献类型：
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作者：
K. Fujimoto;Hidenori Hamaguchi;Takafumi Hashiba;Tadahiro Nakamura;T. Kawamoto;F. Sato;M. Noshiro;U. Bhawal;Ketut Suardita;Y. Kato
DEC2是碱性螺旋-环-螺旋超家族的一员，已被证明具有转录抑制因子的功能，并与细胞的增殖和分化有关。此外，Dec2转录本在视交叉上核表现出显著的昼夜节律振荡。为了确定Dec2调控基因表达的分子机制，我们进行了结构-功能分析。凝胶滞留和荧光素酶分析表明，Dec2及其相关蛋白Dec1以同源二聚体的形式优先与B类E盒元件(CACGTG)结合，并以组蛋白脱乙酰酶(HDAC)依赖的方式抑制靶基因的转录。对GAL4-DNA结合域融合蛋白的功能研究发现，DEC2在其C末端区域具有抑制活性的结构域，这也是招募HDAC1所必需的。此外，DEC2的碱性结构域和HLH域分别是DNA结合和同源二聚所必需的。相反，DEC蛋白通过A类E-box以不依赖于HDAC1的方式抑制肌肉肌酸激酶基因的MyoD激活的启动子活性。DEC2通过碱性结构域和HLH域与MyoD形成异二聚体。与此一致的是，DEC2抑制MyoD转录活性的能力既需要碱性结构域，也需要HLH域。这些发现表明，Dec2采用多种机制，包括DNA结合和蛋白质-蛋白质相互作用，实现E-box依赖的转录表达。
Dec2, a member of the basic helix-loop-helix (bHLH) superfamily, has been shown to function as a transcriptional repressor and is implicated in cell proliferation and differentiation. In addition, Dec2 transcripts exhibit a striking circadian oscillation in the suprachiasmatic nucleus. To identify the molecular mechanisms by which Dec2 regulates gene expression, we carried out structure-function analyses. Gel retardation and luciferase assays showed that Dec2, as well as its related protein Dec1, preferentially binds to class B E-box elements (CACGTG) as a homodimer and represses the transcription of target genes in a histone deacetylase (HDAC)-dependent manner. Functional studies with the GAL4-DNA binding domain fusion proteins identified the domain responsible for the repression activity of Dec2 in its C-terminal region, which is also necessary to recruit HDAC1. In addition, the basic and HLH domains of Dec2 were required for DNA binding and homodimerization, respectively. In contrast, Dec proteins repressed a MyoD-activated promoter activity of muscle creatine kinase gene through class A E-box in an HDAC1-independent manner. Dec2 formed a heterodimer with MyoD through the basic and HLH domains. Consistent with this, both the basic and HLH domains were required for the ability of Dec2 to inhibit the transcriptional activity of MyoD. These findings indicate that Dec2 employs multiple mechanisms, including DNA-binding and protein-protein interactions, to achieve E-box-dependent transcriptional repressions.