Identification and functional characterization of human glycerol-3-phosphate acyltransferase 1 gene promoters.
Identification and functional characterization of human glycerol-3-phosphate acyltransferase 1 gene promoters.
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DOI：
10.1016/j.bbrc.2012.05.094
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发表时间：
2012-06
影响因子：
3.1
通讯作者：
N. Harada;E. Fujimoto;Maiko Okuyama;H. Sakaue;Y. Nakaya
中科院分区：
文献类型：
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作者：
N. Harada;E. Fujimoto;Maiko Okuyama;H. Sakaue;Y. Nakaya
甘油-3-磷酸酰基转移酶1（GPAT 1）在哺乳动物中作为三酰甘油和磷脂合成的限速酶。GPAT 1调节与代谢紊乱相关的肝脏脂质蓄积。在这里，我们已经确定了两个转录起始位点和两个启动子（启动子I和II）所需的人GPAT 1（hGPAT 1）基因的表达。启动子I调节三种可选的hGPAT 1 mRNA变体hGPAT 1-V1、V2和V3的转录，而启动子II诱导第四种变体hGPAT 1-V4的表达。RT-PCR分析和荧光素酶报告基因分析显示，启动子II在脂肪生成组织如肝脏（和肝脏衍生的HepG 2细胞）中起作用，而启动子I受到差异调节，并且也在非肝脏HeLa细胞中起作用。在肝脏富集的转录因子中，HNF 4 α和C/EBPα轻微激活hGPAT 1启动子I，而包括HNF 1 α在内的因子改变启动子II的活性。脂肪生成转录因子SREBP 1c在HepG 2细胞中大大增加了启动子II的活性。使用各种截短或突变片段的启动子II显示，一个甾醇调控元件样基序和一个倒CCAAT盒启动子II促成SREBP 1c的反应。这些顺式作用元件和反式作用因子可能是操纵人类肝脏GPAT 1水平的潜在靶点。
Glycerol-3-phosphate acyltransferase 1 (GPAT1) acts as a rate limiting enzyme in triacylglycerol and phospholipid synthesis in mammals. GPAT1 regulates hepatic lipid accumulation associated with metabolic disorders. Here we have identified two transcriptional initiation sites and two promoters (promoter I and II) required for expression of the human GPAT1 (hGPAT1) gene. Promoter I regulates transcription of three alternative hGPAT1 mRNA variants, hGPAT1-V1, V2, and V3, while promoter II induces expression of a fourth variant, hGPAT1-V4. RT-PCR analysis and luciferase reporter assays revealed that promoter II acts in lipogenic tissues like the liver (and liver-derived HepG2 cells), whereas promoter I is differentially regulated and also acts in non-liver HeLa cells. Among liver-enriched transcription factors, HNF4α and C/EBPα slightly activated hGPAT1 promoter I, while factors including HNF1α altered promoter II activity. The lipogenic transcription factor SREBP1c greatly increased promoter II activity in HepG2 cells. The use of various truncated or mutated fragments of promoter II revealed that one sterol regulatory element-like motif and one inverted CCAAT box on promoter II contributed to the SREBP1c response. These cis-acting elements and trans-acting factors can be potential targets for manipulation of hepatic GPAT1 levels in humans.