Cell-type specific and differential regulation of the human metallothionein genes. Correlation with DNA methylation and chromatin structure.

N Jahroudi,R Foster,J Price-Haughey,G Beitel,L Gedamu

doi:10.1016/s0021-9258(19)39356-1

Abstract

The expression of three human metallothionein genes, MT-IIA, MT-IF, and MT-IG was studied in the human hepatoblastoma (HepG2), the hepatocarcinoma (Hep3B2), the embryonic kidney (Hek 293), and the lymphoblastoid-derived (Wi-L2) cell lines. The pattern of expression of each specific MT gene in response to various heavy metals was different among the four cell lines studied indicating differential regulation of MT gene expression. The MT-IF or MT-IG and the MT-IIA genes were regulated in a cell-type specific manner in response to heavy metals and dexamethasone, respectively. DNA methylation was shown to be correlated to cell-type specific regulation of MT gene expression since 5-azacytidine treatment resulted in the expression of the MT-IF and MT-IG genes in response to cadmium and zinc in Wi-L2 cells, of the MT-IIA gene in response to dexamethasone in Wi-L2 cells, and of the MT-IG in response to zinc and copper in Hek 293 cells. Furthermore, transfection studies indicated that all the trans-acting factors necessary for the expression of these genes were present and functional in Wi-L2 and Hek 293 cells. The differential level of expression of the MT-IF and MT-IG genes in response to heavy metals in the Hek 293 cell line was shown to be correlated to their chromatin structure.

Highlights

DNA methylation was shown to be correlated to cell-type specific regulation of MT gene expression since 5-azacytidine treatment resulted in the expression of the MT-IF and MT-IG genes in response to cadmium and zinc in Wi-LB cells, of the MT-IIA gene in response to dexamethasone in Wi-L2 cells, and of the MT-IG in response to zinc and copper in Hek 293 cells
In order to further address the question of cell-type specific and differential regulation of the human MT gene family and to gain a better understanding of the molecular mechanisms of regulation, we have investigated the expression of the MT-IIA, MT-IF, and MT-IG genes in response to heavy metals and dexamethasone, a glucocorticoid analogue, in the human hepatoblastoma (HepGZ), hepatocarcinoma (Hep3B2), embryonic kidney (Hek 293), and lymphoblastoidderived (Wi-LB) cell lines
To begin characterization of human MT gene expression, we have examined the accumulation of total MT mRNA in response to optimal concentrations of four inducers in four human cell lines over

Summary

AND CHROMATIN STRUCTURE*

The pattern of expression of each specific MT gene in response to various heavy metals was different among the four cell lines studied indicating differential regulation of MT gene expression. In order to further address the question of cell-type specific and differential regulation of the human MT gene family and to gain a better understanding of the molecular mechanisms of regulation, we have investigated the expression of the MT-IIA, MT-IF, and MT-IG genes in response to heavy metals and dexamethasone, a glucocorticoid analogue, in the human hepatoblastoma (HepGZ), hepatocarcinoma (Hep3B2), embryonic kidney (Hek 293), and lymphoblastoidderived (Wi-LB) cell lines. Our results indicate that the MT-IF and MT-IG genes are expressed in a cell-type specific manner and are differentially regulated in response to heavy metals. DNA methylation was correlated to: (i) cell-type specific expression of the MT-IF and MT-IG genes; (ii) cell-type induction of the MT-IIA gene in response to dexamethasone in Wi-L2 cells and; (iii) cell-type specific induction of MT-IG gene in response to zinc and copper in Hek 293 cells

MATERIALS AND METHODS

RESULTS AND DISCUSSION

Barn HI