Promoter analysis of the human ascorbic acid transporters SVCT1 and 2: mechanisms of adaptive regulation in liver epithelial cells.
Promoter analysis of the human ascorbic acid transporters SVCT1 and 2: mechanisms of adaptive regulation in liver epithelial cells.
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DOI：
10.1016/j.jnutbio.2010.03.001
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发表时间：
2011-04
影响因子：
5.6
通讯作者：
Rubin, Stanley A.
中科院分区：
文献类型：
--
作者：
Reidling, Jack C.;Rubin, Stanley A.
抗坏血酸是维生素C的活性形式，是人体肝脏中一种重要的抗氧化剂，然而肝细胞中抗坏血酸转运蛋白（hSVCT1和hSVCT2）调控的分子机制尚不清楚。因此，我们在培养的人肝上皮细胞（HepG2）中表征了hSVCT1和2的最小启动子区域，并研究了抗坏血酸剥夺和补充对运输系统活性和调节的影响。已确定的基础活性所需的最小启动子包括多个顺式调控元件，而突变分析表明，hSVCT1启动子中的HNF-1位点和hSVCT2启动子中的KLF/Sp1位点对活性至关重要。当在抗坏血酸缺乏或补充培养基中培养时，HepG2细胞在[14C]-抗坏血酸摄取、hSVCT1 mRNA和蛋白水平以及hSVCT1启动子活性方面表现出显著（P < 0.01）和特异性的交互变化。然而，在抗坏血酸缺乏或补充条件下，没有观察到hSVCT2表达或启动子活性的显著变化。我们绘制了hSVCT1启动子中的抗坏血酸反应区域，并确定HNF-1位点对适应性调节反应很重要。这些研究的结果进一步表征了hSVCT1和2启动子，证实了抗坏血酸对人肝上皮细胞的摄取受到适应性调节，并表明hSVCT1启动子中HNF-1的转录机制可能部分参与了这种调节。
Ascorbic acid, the active form of vitamin C, is a vital antioxidant in the human liver, yet the molecular mechanisms involved in the regulation of ascorbic acid transporters (hSVCT1 and hSVCT2) in liver cells are poorly understood. Therefore, we characterized the minimal promoter regions of hSVCT1 & 2 in cultured human liver epithelial cells (HepG2) and examined the effects of ascorbic acid deprivation and supplementation on activity and regulation of the transport systems. Identified minimal promoters required for basal activity were found to include multiple cis-regulatory elements, whereas mutational analysis demonstrated that HNF-1 sites in the hSVCT1 promoter and KLF/Sp1 sites in the hSVCT2 promoter were essential for activities. When cultured in ascorbic acid deficient or supplemented media, HepG2 cells demonstrated significant (P < 0.01) and specific reciprocal changes in [14C]-Ascorbic acid uptake, and in hSVCT1 mRNA and protein levels as well as hSVCT1 promoter activity. However, no significant changes in hSVCT2 expression or promoter activity were observed during ascorbic acid deficient or supplemented conditions. We mapped the ascorbic acid responsive region in the hSVCT1 promoter and determined that HNF-1 sites are important for the adaptive regulation response. The results of these studies further characterize the hSVCT1 and 2 promoters, establish that ascorbic acid uptake by human liver epithelial cells is adaptively regulated, and show that transcriptional mechanisms via HNF-1 in the hSVCT1 promoter may, in part, be involved in this regulation.
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DOI：
10.1006/bbrc.1999.1272
发表时间：
1999-09-07
影响因子：
3.1
作者：
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通讯作者：
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10.1152/ajpgi.90399.2008
发表时间：
2008-12-01
影响因子：
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作者：
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作者：
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