Genomic instability and catalase gene amplification induced by chronic exposure to oxidative stress.
Genomic instability and catalase gene amplification induced by chronic exposure to oxidative stress.
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发表时间：
1998-09
期刊：
影响因子：
11.2
通讯作者：
C. Hunt;J. E. Sim;S. Sullivan;T. Featherstone;W. Golden;C. von Kapp-Herr;R. Hock;R. A. Gomez;A. Parsian;D. Spitz
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作者：
C. Hunt;J. E. Sim;S. Sullivan;T. Featherstone;W. Golden;C. von Kapp-Herr;R. Hock;R. A. Gomez;A. Parsian;D. Spitz
HA 1成纤维细胞长期暴露（>200天）于增加浓度的H2 O2或O2导致发展稳定的抗氧化应激表型，其特征在于增加的细胞抗氧化剂水平，特别是过氧化氢酶（D. R. Spitz等人，Arch. Biochem. Biophys.，279：249-260，1990; D. R. Spitz等人，生物化学与生物物理学，292：221-227，1992; S. J. Sullivan等人，Am. J. Physiol.（Lung Cell.摩尔生理学），262：L748-L756，1992）。急性应激细胞未能发展稳定的耐药表型或增加过氧化氢酶活性，表明慢性暴露是需要这种表型的发展。本研究探讨的机制增加过氧化氢酶活性的H2 O2和O2抗性细胞系。在H2 O2-和O2-抗性细胞中，过氧化氢酶活性被发现是20-30倍高于在亲本HA 1细胞中，并与增加的免疫反应性过氧化氢酶蛋白和稳态过氧化氢酶mRNA水平。通过Southern印迹分析，抗性细胞系还显示过氧化氢酶基因拷贝数增加4-6倍，这指示基因扩增。染色体显带和原位杂交研究确定了一个单一的扩增过氧化氢酶基因位点位于重排的染色体与Z-4的仓鼠成纤维细胞核型带相似性。与Z-4特异性腺嘌呤磷酸核糖转移酶（APRT）基因的同时原位杂交显示，扩增的过氧化氢酶基因位于同一染色体上的所有抗性细胞接近APRT。相比之下，HA 1细胞只含有单一拷贝的过氧化氢酶基因，不位于含APRT的染色体上，表明扩增与染色体重排可能涉及Z-4。HA 1细胞长期暴露于HO 2或95%O2导致基因扩增的事实表明，基因扩增代表了对氧化应激的普遍反应，有助于耐药表型的发展。这些结果支持的假设，慢性暴露于内源性代谢或外源性环境氧化应激是一个重要因素，有助于基因扩增和基因组不稳定性。
Chronic exposure (>200 days) of HA1 fibroblasts to increasing concentrations of H2O2 or O2 results in the development of a stable oxidative stress-resistant phenotype characterized by increased cellular antioxidant levels, particularly catalase (D. R. Spitz et al, Arch. Biochem. Biophys., 279: 249-260, 1990; D. R. Spitz et al., Arch. Biochem. Biophys., 292: 221-227, 1992; S. J. Sullivan et al., Am. J. Physiol. (Lung Cell. Mol. Physiol.), 262: L748-L756, 1992). Acutely stressed cells failed to develop a stably resistant phenotype or increased catalase activity, suggesting that chronic exposure is required for the development of this phenotype. This study investigates the mechanism underlying increased catalase activity in the H2O2- and O2-resistant cell lines. In H2O2- and O2-resistant cells, catalase activity was found to be 20-30-fold higher than that in the parental HA1 cells and correlated with increased immunoreactive catalase protein and steady-state catalase mRNA levels. Resistant cell lines also demonstrated a 4-6-fold increase in catalase gene copy number by Southern blot analysis, which is indicative of gene amplification. Chromosome banding and in situ hybridization studies identified a single amplified catalase gene site located on a rearranged chromosome with banding similarities to Z-4 in the hamster fibroblast karyotype. Simultaneous in situ hybridization with a Z-4-specific adenine phosphoribosyltransferase (APRT) gene revealed that the amplified catalase genes were located proximate to APRT on the same chromosome in all resistant cells. In contrast, HA1 cells contained only single copies of the catalase gene that were not located on APRT-containing chromosomes, indicating that amplification is associated with a chromosomal rearrangement possibly involving Z-4. The fact that chronic exposure of HA1 cells to either HO2 or 95% O2 resulted in gene amplification suggests that gene amplification represents a generalized response to oxidative stress, contributing to the development of resistant phenotypes. These results support the hypothesis that chronic exposure to endogenous metabolic or exogenous environmental oxidative stress represents an important factor contributing to gene amplification and genomic instability.