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Human rad21 gene, hHR21(SP), is downregulated by hypoxia in human tumor cells
M Sook Kim1, J Hyen Baek, M K Bae
1Department of Molecular Biology, Pusan National University, Pusan, 609-735, Korea.
Abstract:
To identify genes differentially expressed under normoxic (21% O(2)) or hypoxic (1% O(2)) conditions, we used the technique of mRNA differential display using total RNA extracted from Chang human liver cells. Among downregulated genes by hypoxia, we focused on hHR21(SP) (human homologue of rad21 S. pombe) that is involved in DNA double-strand break repair. Northern blot analysis revealed that mRNA expression of hHR21(SP) was inhibited by hypoxia in various tumor cell lines, such as HepG2, SKHep1, MCF7, and HT1080 cells. We also found that hypoglycemia and heat shock significantly decreased the hHR21(SP) level, indicating that a DNA double-strand break repair gene, hHR21(SP) might be regulated by environmental stresses. In addition, wortmannin, a DNA-dependent protein kinase (DNA-PK) inhibitor, decreased the level of hHR21(SP) mRNA, indicating that DNA-PK might be involved in the regulation of hHR21(SP). These results propose a new understanding of hHR21(SP) regulations in human tumor cells.
Insights
Hypoxia downregulates the DNA repair gene hHR21(SP) in human tumor cells. Environmental stresses and DNA-PK may regulate this gene, offering new insights into its function in cancer.
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Biology
Background:
- Hypoxia, a hallmark of solid tumors, significantly alters gene expression.
- DNA double-strand break repair pathways are crucial for maintaining genomic stability in cancer cells.
Purpose of the Study:
- To identify genes differentially expressed under hypoxic conditions.
- To investigate the regulation of the DNA repair gene hHR21(SP) in human tumor cells.
Main Methods:
- Differential display of mRNA from Chang human liver cells under normoxic and hypoxic conditions.
- Northern blot analysis to assess hHR21(SP) mRNA expression in various tumor cell lines.
- Treatment with wortmannin, a DNA-dependent protein kinase (DNA-PK) inhibitor.
Main Results:
- Hypoxia significantly downregulated hHR21(SP) mRNA expression in multiple tumor cell lines (HepG2, SKHep1, MCF7, HT1080).
- Hypoglycemia and heat shock also decreased hHR21(SP) levels, suggesting regulation by environmental stresses.
- Wortmannin treatment reduced hHR21(SP) mRNA levels, implicating DNA-PK in its regulation.
Conclusions:
- The DNA double-strand break repair gene hHR21(SP) is downregulated by hypoxia in human tumor cells.
- Environmental stresses and DNA-PK signaling pathways are involved in the regulation of hHR21(SP).
- These findings provide novel insights into the regulation of hHR21(SP) in the context of human cancer.