The insulin-like growth factor-binding protein 1 gene is a primary target of peroxisome proliferator-activated receptors
The insulin-like growth factor-binding protein 1 gene is a primary target of peroxisome proliferator-activated receptors
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DOI：
10.1074/jbc.m605623200
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发表时间：
2006-12-22
影响因子：
4.8
通讯作者：
Carlberg, Carsten
中科院分区：
文献类型：
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作者：
Degenhardt, Tatjana;Matilainen, Merja;Carlberg, Carsten
胰岛素样生长因子结合蛋白-1(IGFBP-1)是代谢性和增生性疾病的生物标志物。与此同时，核受体过氧化物酶体增殖物激活受体(PPAR)在代谢综合征和各种癌症的发生发展中起着关键作用。在这里，我们证明，在人肝细胞癌细胞和正常小鼠肝脏中，IGFBP-1mRNA的表达受PPAR配体的初级调控。我们应用一种改进的PPAR反应元件(PPRE)的电子筛选方法，确定了位于IGFBP-1基因转录起始点(TSS)10kb内的5个候选PPRE。染色质免疫沉淀分析表明，在活细胞中，在-1200位(相对于TSS)包含最近端PPRE的基因组区域优先与多种PPAR亚型和转录装置的其他组件结合，包括它们的异二聚体伙伴、维甲酸X受体以及磷酸化的RNA聚合酶II、共阻遏蛋白、共激活蛋白和介质蛋白。此外，进一步的染色质免疫沉淀分析表明，IGFBP-1基因的TSS区以及相关的IGFBP-2、-5和-6基因的TSS区，而不是IGFBP-3和-4基因的TSS区，也与PPAR结合。我们还发现，这些额外的PPAR结合基因包含一些候选的PPRE，它们的mRNA水平对PPAR配体的存在做出快速反应，表明它们也是PPAR的主要靶基因。
Insulin-like growth factor-binding protein 1 (IGFBP-1) is a biomarker for metabolic and hyperproliferative diseases. At the same time, the nuclear receptors peroxisome proliferator-activated receptors (PPARs) are known for their critical role in the development of both the metabolic syndrome and various cancers. Here we demonstrate, in human hepatocellular carcinoma cells and in normal mouse liver, that IGFBP-1 mRNA expression is under the primary control of PPAR ligands. We applied an improved in silico screening approach for PPAR response elements (PPREs) and identified five candidate PPREs located within 10 kb of the transcription start site (TSS) of the IGFBP-1 gene. Chromatin immunoprecipitation assays showed that, in living cells, the genomic region containing the most proximal PPRE, at position -1200 (relative to the TSS), preferentially associates with multiple PPAR subtypes and various other components of the transcriptional apparatus, which include their heterodimerizing partner, retinoid X receptor, as well as phosphorylated RNA polymerase II, co-repressor, co-activator, and mediator proteins. Moreover, further chromatin immunoprecipitation assays demonstrated that the TSS regions of the IGFBP-1 gene and those of the related IGFBP-2, -5, and -6, but not of IGFBP-3 and -4 genes, bind PPARs as well. We also show that these additional PPAR binding genes contain a number of candidate PPREs and that their mRNA levels respond quickly to the presence of PPAR ligands, indicating that they are also primary PPAR target genes.