A novel functional interaction between the Sp1-like protein KLF13 and SREBP-Sp1 activation complex underlies regulation of low density lipoprotein receptor promoter function
A novel functional interaction between the Sp1-like protein KLF13 and SREBP-Sp1 activation complex underlies regulation of low density lipoprotein receptor promoter function
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DOI：
10.1074/jbc.m509417200
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发表时间：
2006-02-10
影响因子：
4.8
通讯作者：
Veldhuis, JD
中科院分区：
文献类型：
--
作者：
Natesampillai, S;Zapico, ME;Veldhuis, JD
胆固醇稳态是由一系列被称为固醇调节元件结合蛋白（SREBPs）的转录因子调控的。精确控制srebp靶向基因需要与共调控转录因子的额外相互作用。在低密度脂蛋白受体（LDLR）的情况下，SREBP与特异性蛋白Sp1合作激活启动子。在本报告中，我们描述了一种不同于SREBP-Sp1激活复合物的LDLR转录调控新途径，涉及sp1样蛋白krueppel样因子13 （KLF13）。通过结合RNA干扰、电泳迁移、染色质免疫沉淀、报告基因测定、缺失和位点定向诱变，我们证明了KLF13以DNA上下文选择性的方式介导抑制。KLF13抑制LDLR启动子活性似乎是保持受体沉默所必需的，这种状态可以被Sp1、SREBP和组蛋白去乙酰化酶活性抑制剂拮抗。染色质免疫沉淀法证实，KLF13在体内结合LDLR近端DNA序列，外源氧甾醇上调这种结合。这些研究共同确定了一种新的调控途径，在该途径中，Sp1-SREBP复合体必须克服KLF13的基因抑制才能激活LDLR启动子。因此，这些数据应该取代先前存在的更简单的范式，即只考虑LDLR启动子驱动所必需的激活蛋白Sp1-SREBP的诱导，而不包括LDLR基因的默认抑制，如KLF13。
Cholesterol homeostasis is regulated by a family of transcription factors designated sterol regulatory element-binding proteins ( SREBPs). Precise control of SREBP-targeted genes requires additional interactions with co-regulatory transcription factors. In the case of the low density lipoprotein receptor ( LDLR), SREBP cooperates with the specificity protein Sp1 to activate the promoter. In this report, we describe a novel pathway in LDLR transcriptional regulation distinct from the SREBP-Sp1 activation complex involving the Sp1-like protein Krueppel-like factor 13 ( KLF13). Using a combination of RNA interference, electrophoretic mobility shift, chromatin immunoprecipitation, and reporter assays, deletion, and site-directed mutagenesis, we demonstrated that KLF13 mediates repression in a DNA context-selective manner. KLF13 repression of LDLR promoter activity appears to be needed to keep the receptor silent, a state that can be antagonized by Sp1, SREBP, and inhibitors of histone deacetylase activity. Chromatin immunoprecipitation assay confirmed that KLF13 binds proximal LDLR DNA sequences in vivo and that exogenous oxysterol up-regulates such binding. Together these studies identify a novel regulatory pathway in which gene repression by KLF13 must be overcome by the Sp1-SREBP complex to activate the LDLR promoter. Therefore, these data should replace a pre-existent and more simple paradigm that takes into consideration only the induction of the activator proteins Sp1-SREBP as necessary for LDLR promoter drive without including default repression, such as that by KLF13, of the LDLR gene.