The SRE Motif in the Human PNPLA3 Promoter (-97 to-88bp) Mediates Transactivational Effects of SREBP-1c
The SRE Motif in the Human PNPLA3 Promoter (-97 to-88bp) Mediates Transactivational Effects of SREBP-1c
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DOI：
10.1002/jcp.24951
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发表时间：
2015-09-01
影响因子：
5.6
通讯作者：
Weng, Jianping
中科院分区：
文献类型：
--
作者：
Liang, Hua;Xu, Jing;Weng, Jianping
Patatin-like phospholipase domain containing 3（PNPLA 3）是一种主要在肝脏和脂肪组织中表达的非分泌性蛋白。近年来，大量的遗传学研究表明PNPLA 3是非酒精性脂肪性肝病（NAFLD）的主要易感基因。然而，PNPLA 3基因的转录调控机制仍不清楚。我们对人PNPLA 3基因启动子进行了详细的分析，并鉴定了两个新的顺式作用元件（SRE和NFY结合基序），分别位于-97/-88和-26/-22bp。在HepG 2细胞中过表达SREBP-1c显著增加PNPLA 3启动子活性。假定的SRE或NFY结合基序的突变阻断了SREBP-1c对启动子的反式激活作用。SREBP-1c和NFY共同过表达增加PNPLA 3启动子活性是SREBP-1c或NFY单独表达的两倍。该结果表明，SREBP-1c和NFY协同反式激活人PNPLA 3基因。使用凝胶位移分析证实SREBP-1c和NFY结合这些顺式元件的能力。推测的SRE和NFY基序也介导了HepG 2细胞中PNPLA 3启动子的协同胰岛素诱导的反式激活。此外，SREBP-1c与PNPLA 3启动子结合的能力通过胰岛素以剂量依赖性方式增加。此外，用PI 3 K抑制剂LY 294002处理HepG 2细胞导致胰岛素启动子激活能力降低，伴随着PNPLA 3和SREBP-1c蛋白表达的降低。这些结果表明，SREBP-1c是人PNPLA 3基因的直接激活剂，并且胰岛素在HepG 2细胞中通过PI 3 K-SREBP-1c/NFY途径反式激活PNPLA 3基因。J.细胞。230：2224-2232，2015。(c)2015 Wiley Periodicals，Inc.
Patatin-like phospholipase domain containing 3 (PNPLA3) is a non-secreted protein primarily expressed in liver and adipose tissue. Recently, numerous genetic studies have shown that PNPLA3 is a major susceptibility gene for nonalcoholic fatty liver disease (NAFLD). However, the mechanism involved in transcriptional regulation of the PNPLA3 gene remains unknown. We performed a detailed analysis of the human PNPLA3 gene promoter and identified two novel cis-acting elements (SRE and NFY binding motifs) located at -97/-88 and -26/-22bp, respectively. Overexpression of SREBP-1c in HepG2 cells significantly increased PNPLA3 promoter activity. Mutation of either of the putative SRE or NFY binding motifs blocked the transactivation effects of SREBP-1c on the promoter. Overexpression of SREBP-1c and NFY together increased PNPLA3 promoter activity twice as much as that of SREBP-1c or NFY expression alone. This result suggests that SREBP-1c and NFY synergistically transactivate the human PNPLA3 gene. The ability of SREBP-1c and NFY to bind these cis-elements was confirmed using gel shift analysis. Putative SRE and NFY motifs also mediated synergistic insulin-induced transactivation of the PNPLA3 promoter in HepG2 cells. Additionally, the ability of SREBP-1c to bind to the PNPLA3 promoter was increased by insulin in a dose-dependent manner. Moreover, the treatment of HepG2 cells with the PI3K inhibitor LY294002 led to reduced insulin promoter-activating ability accompanied by a decrease in PNPLA3 and SREBP-1c protein expression. These results demonstrate that SREBP-1c is a direct activator of the human PNPLA3 gene and insulin transactivates the PNPLA3 gene via the PI3K-SREBP-1c/NFY pathway in HepG2 cells. J. Cell. Physiol. 230: 2224-2232, 2015. (c) 2015 Wiley Periodicals, Inc.