Zinc depletion reduced Egr-1 and HNF-3beta expression and apolipoprotein A-I promoter activity in Hep G2 cells.
We examined the influence of zinc status on expression of certain transcription factors involved in regulation of apolipoprotein A-I (apoAI) expression in human hepatoblastoma Hep G2 cells. A low zinc basal medium (zinc deficient, ZD) consisting of DMEM and 10% Chelex100-treated fetal bovine serum was used to deplete cellular zinc over one passage. Cells were also cultured for one passage in medium supplemented with 0.4 (ZD0.4), 4.0 (zinc normal, ZN), 16.0 (zinc adequate, ZA), or 32.0 microM zinc (zinc supplemented, ZS). Compared with ZN cells, cellular zinc levels were 43 and 31% lower in ZD and ZD0.4 cells but 70 and 146% higher in ZA and ZS cells, respectively. Supplementation of 0.4 microM zinc significantly increased DNA contents per plate, from 65% in ZD cells to 83% in ZD0.4 cells compared with ZN cells. Addition of >4 microM zinc in medium did not further increase DNA contents. The proportion of cells in G(1)/S and S phase was about fourfold higher and threefold lower, respectively, in ZD cells compared with ZN and other groups. Nuclear Egr-1 protein was markedly decreased in ZD and ZD0.4 cells. Moreover, hepatocyte nuclear factor (HNF)-3beta was severely degraded in ZD and ZD0.4 cells. In contrast, HNF-4alpha remained stable in all groups and was not significantly lower in ZD and ZD0.4 cells. Furthermore, downregulation of trans-acting factor Egr-1 and cleavage of HNF-3beta were associated with reduction of apoAI promoter activity in zinc-deficient Hep G2 cells. Thus zinc is critical in transcriptional regulation of apoAI gene expression in hepatocytes.
Cui
Libin
L
Department of Nutrition and Food Science, University of Maryland, College Park 20742, USA.
Schoene
Norberta W
NW
Zhu
Lei
L
Fanzo
Jessica C
JC
Alshatwi
Ali
A
Lei
K Y
KY
D016632:Apolipoprotein A-I / Q000235:genetics*; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D002453:Cell Cycle; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D051766:Early Growth Response Protein 1; D016193:G1 Phase; D018197:Hepatoblastoma / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D051542:Hepatocyte Nuclear Factor 3-beta; D051557:Hepatocyte Nuclear Factor 4; D006801:Humans; D017874:Immediate-Early Proteins; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology*; D016196:S Phase; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D015032:Zinc / Q000172:deficiency* / Q000378:metabolism / Q000494:pharmacology
D016632:Apolipoprotein A-I; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; C496502:FOXA2 protein, human; C496592:HNF4A protein, human; D051557:Hepatocyte Nuclear Factor 4; D017874:Immediate-Early Proteins; C403128:MLX protein, human; D009687:Nuclear Proteins; D010750:Phosphoproteins; D014157:Transcription Factors; D051542:Hepatocyte Nuclear Factor 3-beta; D004247:DNA; D015032:Zinc