Copper Alters the Conformation and Transcriptional Activity of the Tumor Suppressor Protein p53 in Human Hep G2 Cells

Abstract

The tumor suppressor protein p53 plays a role in the molecular response to DNA damage by acting as a DNA-binding transcription factor that regulates specific target genes to arrest the cell cycle, induce repair mechanisms, and initiate apoptotic cell death. To test the effect of copper on the transcriptional activity of p53, Hep G2 cells were transiently transfected with a luciferase reporter gene downstream from multiple p53 response elements. Co-transfection with the p53 gene resulted in a 6-fold increase in luciferase activity, showing that p53 acts as a transcription factor in this system. However, in the presence of copper, luciferase activity was significantly reduced. Oligonucleotide arrays representing 145 known p53-associated genes were hybridized with biotinylated cDNAs from mRNA extracted from control and copper-treated Hep G2 cells. Among the genes that were differentially regulated were fos, RB1, glutathione peroxidase, TGF-beta, and 15-lipoxygenase, a gene known to be activated by mutant p53. Although control Hep G2 cells synthesize wild-type p53, immunocytochemistry identified not only wild type, but also mutant p53 in the presence of copper and other agents that induce oxidative damage. Thus, this report not only identifies genes that may play a role in copper-mediated apoptosis, but also suggests that copper-induced oxidative processes result in the synthesis of mutant p53 with altered transcriptional properties.

Acute and subchronic copper treatments alter extracellular nucleotide hydrolysis in zebrafish brain membranes

“…Moreover, the expression patterns of NTPDase2 mq and ecto-5 -nucleotidase transcripts were also reduced after subchronic treatment. Previous study has shown the effect of copper on gene expression, demonstrating that this metal may be able to regulate the transcriptional activity of human p53 protein (Tassabehji et al, 2005). Therefore, the lower NTPDase1, NTPDase2 mg and NTPDase2 mv after both treatments and the inhibition of NTPDase2 mq and ecto-5 -nucleotidase expression after a 96-h copper exposure could be one of the mechanisms involved in the inhibition of nucleotide hydrolysis in zebrafish brain membranes.…”

Impact of copper on the induction and repair of oxidative DNA damage, poly(ADP‐ribosyl)ation and PARP‐1 activity

“…The tumour suppressor protein p53 also contains a zinc binding domain, which is responsible for DNA binding and its function as transcription factor. Tassabehji et al [54] provided evidence that copper alters the conformation and transcriptional activity of p53 in human Hep G2 cells and just recently p53 has been assumed to be the major regulator of the expression and activity of the human 8-oxoguanin-DNA glycosylase (hOgg1) [55]. hOgg1 is responsible for the repair of the oxidative DNA base modification 8-oxoguanine.…”

Role and mechanism of the AMPK pathway in waterborne Zn exposure influencing the hepatic energy metabolism of Synechogobius hasta

“…In the present study, the mRNA levels of genes involved in the DNA fragmentation of apoptosis3132, such as AIF (apoptosis-inducing factor), DFFA (DNA fragmentation factor, 45 kD, alpha subunit) and DFFB (DNA fragmentation factor, 40 kD, beta subunit), were significantly higher in the Zn-treated group than those in the control. In addition, Zn exposure changed the expression levels of calpain and caspase-3 (CASP3), key genes mediating cellular apoptosis33. Together, these changes suggested that excessive Zn exposure also induced DNA damage and apoptosis in the liver of S .…”