Folate deficiency in vitro induces uracil misincorporation and DNA hypomethylation and inhibits DNA excision repair in immortalized normal human colon epithelial cells
Folate deficiency in vitro induces uracil misincorporation and DNA hypomethylation and inhibits DNA excision repair in immortalized normal human colon epithelial cells
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DOI：
10.1207/s15327914nc372_18
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发表时间：
2000-01-01
影响因子：
2.9
通讯作者：
Brand, GM
中科院分区：
文献类型：
--
作者：
Duthie, SJ;Narayanan, S;Brand, GM
流行病学研究表明，叶酸可以预防多种癌症，特别是结肠直肠癌。叶酸对有效的DNA合成和修复至关重要。此外，叶酸可以影响细胞S-腺苷甲硫氨酸水平，其调节DNA甲基化和控制基因表达。我们研究了叶酸影响永生化正常人结肠细胞（HCEC）DNA稳定性的机制。DNA链断裂，尿嘧啶错误掺入，DNA修复，在氧化和烷基化损伤，确定在叶酸充足和叶酸缺乏的结肠细胞通过单细胞凝胶电泳。此外，使用细菌酶Sss 1甲基化酶测量甲基掺入基因组DNA。培养的人结肠细胞DNA含有内源性链断裂和尿嘧啶。叶酸缺乏显着增加链断裂和尿嘧啶错误掺入这些细胞。这种对DNA稳定性的负面影响是浓度依赖性的，其水平通常见于人血浆中（1-10 ng/ml）。在没有叶酸的情况下生长的HCEC中DNA甲基化降低。相反，低甲基化也不是浓度依赖性的。叶酸缺乏损害了HCEC修复氧化和烷基化损伤的能力。这些结果表明，叶酸调节DNA修复DNA链断裂，尿嘧啶错误掺入永生化的人结肠细胞，叶酸缺乏显着降低这些细胞中的DNA稳定性。
Epidemiological studies have indicated that folic acid protects against a variety of cancers, particularly cancer of the colorectum. Folate is essential for efficient DNA synthesis and repair. Moreover folate can affect cellular S-adenosylmethionine levels, which regulate DNA methylation and control gene expression. We have investigated the mechanisms through which folate affects DNA stability in immortalized normal human colonocytes (HCEC). DNA strand breakage, uracil misincorporation, and DNA repair, in response to oxidative and alkylation damage, were determined in folate-sufficient and folate-deficient colonocytes by single cell gel electrophoresis. In addition, methyl incorporation into genomic DNA was measured using the bacterial enzyme Sss1 methylase. Cultured human colonocyte DNA contained endogenous strand breaks and uracil. Folate deficiency significantly increased strand breakage and uracil misincorporation in these cells. This negative effect on DNA stability was concentration dependent at levels usually found in human plasma (1-10 ng/ml). DNA methylation was decreased in HCEC grown in the absence of folate. Conversely, hypomethylation was nor concentration dependent. Folate deficiency impaired the ability of HCEC to repair oxidative and alkylation damage. These results demonstrate that folic acid modulates DNA repair DNA strand breakage, and uracil misincorporation in immortalized human colonocytes and that folate deficiency substantially decreases DNA stability in these cells.