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The redox-sensitive human antioxidant responsive element induces gene expression under low oxygen conditions
N S Waleh1, J Calaoagan, B J Murphy
1Pharmaceutical Discovery Division, SRI International, Menlo Park, CA 94025, USA. nahid_waleh@qm.sri.com
Carcinogenesis
|September 23, 1998
Summary
The antioxidant responsive element (ARE) can regulate gene expression in low oxygen conditions, impacting cellular responses. This finding is crucial for understanding gene regulation in hypoxic tumors and developing targeted therapies.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- The antioxidant responsive element (ARE) is a key regulatory DNA sequence involved in cellular defense mechanisms.
- Understanding ARE function under varying oxygen levels is critical for comprehending cellular adaptation and disease pathology, particularly in hypoxic tumors.
Purpose of the Study:
- To investigate the responsiveness of the NQO1 gene's ARE to hypoxic conditions in liver cancer cells.
- To determine the effect of N-acetyl L-cysteine (NAC) on ARE-mediated gene expression under aerobic and hypoxic conditions.
Main Methods:
- Transient transfection assays using reporter gene constructs in HepG2 and Hepa cells.
- Electrophoretic mobility shift assays (EMS) to analyze protein binding to the ARE.
Main Results:
- The ARE demonstrated responsiveness to low oxygen (hypoxic) conditions.
- N-acetyl L-cysteine (NAC) inhibited basal aerobic reporter gene activity but did not significantly affect hypoxic induction.
- Specific and constitutive protein binding to the ARE was observed under both aerobic and hypoxic conditions.
Conclusions:
- The ARE mediates gene expression in response to hypoxia.
- ARE-dependent genes, including phase II detoxification enzymes, may play a significant role in the phenotype of solid tumors with pathophysiological hypoxia.