Alkaline induces metallothionein gene expression and potentiates cell proliferation in Chinese hamster ovary cells

✍ Scribed by Kuei-Ann Lin; Je-Hsin Chen; Dong-Fong Lee; Lih-Yuan Lin

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 259 KB
• Volume: 205
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.20417

✦ Synopsis

Abstract

Metallothionein (MT) gene expression is increased in cadmium resistant Chinese hamster ovary cells (CHO Cd^R^) upon medium (regular or serum‐free) change during culturing. Among the major components of the medium, NaHCO~3~ was found to be able to induce MT gene expression in a dose‐ and time‐dependent manner. The same effect was observed with other alkaline solutions, such as HEPES and NaOH. Using MT promoter‐luciferase reporter gene constructs, we found that the presence of metal response elements (MREs) in the promoter region is necessary for NaHCO~3~‐induced MT gene transcription. This finding is further supported by the observation that the binding activity between the metal‐responsive transcription factor 1 (MTF‐1) and the MRE were increased after NaHCO~3~ treatment. Following NaHCO~3~ treatment, an increase in cell proliferation was observed in Cd^R^ cells but not in the parental CHO K1 cells that do not express MT transcripts due to MT gene methylation. Using synchronized cells, an increase in cell proliferation was observed 9 h after NaHCO~3~ addition. Notably, proliferation of CHO K1 cells was increased when transfected with an MT gene. The effect of MT on cell growth was affirmed by treating CHO K1 cells with 5‐azacytidine (Aza) to demethylate the MT gene. Proliferation increased in Aza‐treated CHO K1 cells after NaHCO~3~ treatment. These results demonstrate that NaHCO~3~ stimulates MT gene expression and causes an enhancement of cell proliferation in CHO cells. © 2005 Wiley‐Liss, Inc.