Song Min Ok, Freedman Jonathan H
National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA.
Biochim Biophys Acta. 2011 Jan;1813(1):102-8. doi: 10.1016/j.bbamcr.2010.09.009. Epub 2010 Sep 27.
Previous global transcriptome and interactome analyses of copper-treated HepG2 cells identified hepatocyte nuclear factor 4α (HNF4α) as a potential master regulator of copper-responsive transcription. Copper exposure caused a decrease in the expression of HNF4α at both mRNA and protein levels, which was accompanied by a decrease in the level of HNF4α binding to its consensus DNA binding sequence. qRT-PCR and RNAi studies demonstrated that changes in HNF4α expression ultimately affected the expressions of its down-stream target genes. Analysis of upstream regulators of HNF4α expression, including p53 and ATF3, showed that copper caused an increase in the steady-state levels of these proteins. These results support a model for copper-responsive transcription in which the metal affects ATF3 expression and stabilizes p53 resulting in the down-regulation of HNF4α expression. In addition, copper may directly affect p53 protein levels. The suppression of HNF4α activity may contribute to the molecular mechanisms underlying the physiological and toxicological consequences of copper toxicity in hepatic-derived cells.
先前对铜处理的HepG2细胞进行的全基因组转录组和相互作用组分析确定，肝细胞核因子4α（HNF4α）是铜反应性转录的潜在主要调节因子。铜暴露导致HNF4α在mRNA和蛋白质水平的表达均下降，同时HNF4α与其共有DNA结合序列的结合水平也降低。qRT-PCR和RNAi研究表明，HNF4α表达的变化最终影响其下游靶基因的表达。对包括p53和ATF3在内的HNF4α表达上游调节因子的分析表明，铜导致这些蛋白质的稳态水平升高。这些结果支持了一种铜反应性转录模型，其中金属影响ATF3表达并稳定p53，从而导致HNF4α表达下调。此外，铜可能直接影响p53蛋白水平。HNF4α活性的抑制可能有助于解释肝源性细胞中铜毒性的生理和毒理后果的分子机制。
