Bipartite recognition of DNA by TCF/Pangolin is remarkably flexible and contributes to transcriptional responsiveness and tissue specificity of wingless signaling.
Bipartite recognition of DNA by TCF/Pangolin is remarkably flexible and contributes to transcriptional responsiveness and tissue specificity of wingless signaling.
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DOI：
10.1371/journal.pgen.1004591
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发表时间：
2014-09
期刊：
影响因子：
4.5
通讯作者：
Cadigan KM
中科院分区：
文献类型：
--
作者：
Archbold HC;Broussard C;Chang MV;Cadigan KM
T细胞因子家族转录因子是后生动物Wnt/β-catenin信号的主要介导者。所有的TCFs都含有一个高迁移率基团(HMG)结构域，具有特定的DNA结合活性。此外，许多TCFs含有第二个DNA结合域，即C-CLAMP，它与被称为辅助位点的DNA基序结合。虽然HMG和辅助位点对于几个WNT依赖的顺式调节模块(W-CRM)的激活都很重要，但什么构成一个功能性的HMG-辅助位点对的规则尚不清楚。在这份报告中，我们采用了体外结合、报告基因分析和生物信息学相结合的方法，以果蝇家族成员TCF/穿山甲(TCF/PAN)为模型。我们发现，虽然HMG-Helper对的方向和间距有限制，但在任何方向上HMG位点附近的Helper位点的存在都会增加结合和转录反应，有些方向显示出组织特有的模式。我们发现，将HMG-Helper位点对从次优改变为最佳取向/间距，极大地提高了W-CRM在几个苍蝇组织中的响应性。此外，我们利用所获得的知识以生物信息学的方式鉴定了两种新的W-CRM，其中一种是由前胸腺中的Wnt/β-连环蛋白信号激活的，这是一种以前没有连接到这一途径的组织。总之，这项工作扩展了辅助位点在Fly W-CRM中的重要性，并表明HMG-Helper对的类型是设置Wnt激活和组织反应性阈值的主要因素。基因表达的调控在很大程度上是由被称为转录因子的蛋白质控制的，这些蛋白质与基因组中特定的DNA序列结合。转录因子的DNA结合域识别短片段(5-11个碱基对)的DNA，具有相当大的序列简并性。这意味着，单个DNA结合域本身不能在大量的基因组序列中找到它的靶标。我们正在使用Tcf/穿山甲来研究这个问题，这是一种果蝇转录因子，介导Wnt/β-连环蛋白信号，这是一种重要的发育细胞-细胞通讯途径。Tcf/穿山甲包含两个DNA结合域，它们与一对DNA基序结合，称为HMG和Helper位点。我们结合生物化学、遗传学和生物信息学来解释HMG-Helper位点对的间距和方向限制。我们发现，HMG-Helper位点的间距/方向影响了目标对Wnt信号的敏感性，以及它的组织反应性。我们利用这些信息来提高我们搜索果蝇基因组中Wnt靶标的能力，其中一个靶标被昆虫主要内分泌器官苍蝇环腺中的途径激活。我们的工作与相关的哺乳动物TCF家族成员有关，这些成员与发育、干细胞生物学和癌症进展有关。
The T-cell factor (TCF) family of transcription factors are major mediators of Wnt/β-catenin signaling in metazoans. All TCFs contain a High Mobility Group (HMG) domain that possesses specific DNA binding activity. In addition, many TCFs contain a second DNA binding domain, the C-clamp, which binds to DNA motifs referred to as Helper sites. While HMG and Helper sites are both important for the activation of several Wnt dependent cis-regulatory modules (W-CRMs), the rules of what constitutes a functional HMG-Helper site pair are unknown. In this report, we employed a combination of in vitro binding, reporter gene analysis and bioinformatics to address this question, using the Drosophila family member TCF/Pangolin (TCF/Pan) as a model. We found that while there were constraints for the orientation and spacing of HMG-Helper pairs, the presence of a Helper site near a HMG site in any orientation increased binding and transcriptional response, with some orientations displaying tissue-specific patterns. We found that altering an HMG-Helper site pair from a sub-optimal to optimal orientation/spacing dramatically increased the responsiveness of a W-CRM in several fly tissues. In addition, we used the knowledge gained to bioinformatically identify two novel W-CRMs, one that was activated by Wnt/β-catenin signaling in the prothoracic gland, a tissue not previously connected to this pathway. In sum, this work extends the importance of Helper sites in fly W-CRMs and suggests that the type of HMG-Helper pair is a major factor in setting the threshold for Wnt activation and tissue-responsiveness. Regulation of gene expression is controlled in large part by proteins known as transcription factors, which bind to specific DNA sequences in the genome. The DNA binding domains of transcription factors recognize short stretches (5–11 base pairs) of DNA with considerable sequence degeneracy. This means that a single DNA binding domain, on its own, cannot find its targets in the vast excess of genomic sequence. We are studying this question using TCF/Pangolin, a Drosophila transcription factor that mediates Wnt/β-catenin signaling, an important developmental cell-cell communication pathway. TCF/Pangolin contains two DNA binding domains that bind to a pair of DNA motifs known as HMG and Helper sites. We used a combination of biochemistry, genetics and bioinformatics to elucidate the spacing and orientation constraints of HMG-Helper site pairs. We found that HMG-Helper site spacing/orientation influenced the sensitivity of a target to Wnt signaling, as well as its tissue-responsiveness. We used this information to improve our ability to search the Drosophila genome for Wnt targets, one of which was activated by the pathway in the fly ring gland, the major endocrine organ in insects. Our work is relevant to related mammalian TCF family members, which are implicated in development, stem cell biology and the progression of cancer.
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影响因子：
3.7
作者：
Bülow MH;Aebersold R;Pankratz MJ;Jünger MA
通讯作者：
Jünger MA
DOI：
10.1126/science.1162327
发表时间：
2009-06-26
期刊：
Science (New York, N.Y.)
影响因子：
--
作者：
Badis G;Berger MF;Philippakis AA;Talukder S;Gehrke AR;Jaeger SA;Chan ET;Metzler G;Vedenko A;Chen X;Kuznetsov H;Wang CF;Coburn D;Newburger DE;Morris Q;Hughes TR;Bulyk ML
通讯作者：
Bulyk ML
影响因子：
14.9
作者：
Blahnik KR;Dou L;O'Geen H;McPhillips T;Xu X;Cao AR;Iyengar S;Nicolet CM;Ludäscher B;Korf I;Farnham PJ
通讯作者：
Farnham PJ
影响因子：
10.5
作者：
Cole, Megan F.;Johnstone, Sarah E.;Young, Richard A.
通讯作者：
Young, Richard A.
影响因子：
4.6
作者：
Barker, Nick;Tan, Shawna;Clevers, Hans
通讯作者：
Clevers, Hans