FOXO1 cysteine-612 mediates stimulatory effects of the coregulators CBP and PGC1α on FOXO1 basal transcriptional activity
FOXO1 cysteine-612 mediates stimulatory effects of the coregulators CBP and PGC1α on FOXO1 basal transcriptional activity
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DOI：
10.1016/j.freeradbiomed.2018.02.034
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发表时间：
2018-04-01
影响因子：
7.4
通讯作者：
Klotz, Lars-Oliver
中科院分区：
文献类型：
--
作者：
Tsitsipatis, Dimitrios;Gopal, Keshav;Klotz, Lars-Oliver
肝脏代谢产物、营养物质和微量营养素转运蛋白的产生和释放在基因表达水平上受到严格调控。在这方面，转录因子FOXO 1调节基因的表达，如G6 PC和SELENOP，分别编码葡萄糖6-磷酸酶和血浆硒转运蛋白硒蛋白P的催化亚基。在这里，我们分析了FOXO 1中的半胱氨酸残基在控制其活性方面的作用，在HepG 2人肝癌细胞中调节G6 PC和SELENOP。7个FOXO 1半胱氨酸都不影响FOXO 1与DNA的结合或其基础亚细胞分布。而野生型FOXO 1的过表达引起G6 PC和SELENOP启动子活性和mRNA水平的强烈诱导，诱导降低了约。50%，如果半胱氨酸缺陷型FOXO 1过度表达。只有最C-末端的7个FOXO 1半胱氨酸，Cys 612，是必需的，足以确保充分的FOXO 1反式激活活性。FOXO 1辅助调节因子CBP或PGC 1 α的共表达在刺激G6 PC启动子活性和表达方面具有很强的协同效应，完全依赖于FOXO 1 Cys 612的存在。同样，对于SELENOP，观察到FOXO 1和CBP的协同效应。相比之下，PGC 1 α对SELENP的刺激不依赖于FOXO 1-Cys 612，这是由于肝细胞核因子-4 α结合位点与SELENP启动子内的FOXO 1结合位点非常接近，如使用突变型SELENP启动子构建体所证明的。总之，完全的基础FOXO 1反式激活活性依赖于Cys 612，Cys 612介导辅助调节因子CBP或PGC 1 α对FOXO 1转录活性的协同作用。Cys 612的贡献程度取决于FOXO 1靶基因的启动子背景。
Hepatic production and release of metabolites, nutrients and micronutrient transporters is tightly regulated at the level of gene expression. In this regard, transcription factor FOXO1 modulates the expression of genes such as G6PC and SELENOP, encoding the catalytic subunit of glucose 6-phosphatase and the plasma selenium transporter selenoprotein P, respectively. Here, we analyzed the role of cysteine residues in FOXO1 in controlling its activity with respect to regulation of G6PC and SELENOP in HepG2 human hepatoma cells. None of the seven FOXO1 cysteines affected FOXO1 binding to DNA or its basal subcellular distribution. Whereas overexpression of wildtype FOXO1 caused a strong induction of both G6PC and SELENOP promoter activities and mRNA levels, the induction was lowered by approx. 50% if cysteine-deficient FOXO1 was overexpressed instead. Only the most C-terminal of the seven FOXO1 cysteines, Cys612, was required and sufficient to ensure full FOXO1 transactivation activity. Coexpression of FOXO1 coregulators, CBP or PGC1 alpha, had a strong synergistic effect in stimulating G6PC promoter activity and expression, fully relying on the presence of FOXO1 Cys612. Similarly, a synergistic effect of FOXO1 and CBP was observed for SELENOP. In contrast, stimulation of SELENOP by PGC1 alpha was independent of FOXO1-Cys612, due to the close proximity of a hepatocyte nuclear factor-4 alpha binding site to the FOXO1 binding site within the SELENOP promoter, as demonstrated using mutant SELENOP promoter constructs. In summary, full basal FOXO1 transactivation activity relies on Cys612, which mediates synergistic effects of coregulators, CBP or PGC1 alpha, on FOXO1 transcriptional activity. The extent of Cys612 contribution depends on the promoter context of FOXO1 target genes.