Defects in purine nucleotide metabolism lead to substantial incorporation of xanthine and hypoxanthine into DNA and RNA
Defects in purine nucleotide metabolism lead to substantial incorporation of xanthine and hypoxanthine into DNA and RNA
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DOI：
10.1073/pnas.1118455109
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发表时间：
2012-02-14
影响因子：
11.1
通讯作者：
Dedon, Peter C.
中科院分区：
文献类型：
--
作者：
Pang, Bo;McFaline, Jose L.;Dedon, Peter C.
DNA和RNA中核碱基的脱氨导致黄嘌呤（X）、次黄嘌呤（I）、恶嘌呤和尿嘧啶的形成，所有这些在DNA中都是错误编码和致突变的，并且可以干扰RNA编辑和功能。在许多形式的核酸损伤中，脱氨基作用由几种不相关的机制引起，包括水解、亚硝化化学和脱氨酶。在这里，我们提出了第四种机制，有助于核碱基脱氨的负担：次黄嘌呤和黄嘌呤掺入DNA和RNA的嘌呤核苷酸代谢缺陷所造成的。使用嘌呤代谢中具有确定突变的大肠杆菌和酿酒酵母，结合定量DNA和RNA中脱氨基核碱基的分析方法，在不能将IMP转化为XMP或AMP的细胞中，DNA和RNA中的次黄嘌呤（高达600倍）（IMP脱氢酶，guaB;腺苷酸琥珀酸合成酶，purA和ADE 12），并且不能从核苷酸库中去除dITP/ITP和dXTP/XTP（dITP/XTP焦磷酸水解酶，rdgB和HAM 1）。相反，在E.缺乏purA和rdgB的大肠杆菌和将XMP转化为GMP的酶（GMP合成酶，guaA）。这些观察结果表明，由已知的遗传多态性引起的嘌呤代谢紊乱可能会增加DNA中致突变脱氨基核碱基的负担，并干扰基因表达和RNA功能，这种情况可能会因并发炎症的亚硝化应激而加剧。研究结果也为人类先天性嘌呤核苷酸代谢缺陷的病理生理学提供了机制基础。
Deamination of nucleobases in DNA and RNA results in the formation of xanthine (X), hypoxanthine (I), oxanine, and uracil, all of which are miscoding and mutagenic in DNA and can interfere with RNA editing and function. Among many forms of nucleic acid damage, deamination arises from several unrelated mechanisms, including hydrolysis, nitrosative chemistry, and deaminase enzymes. Here we present a fourth mechanism contributing to the burden of nucleobase deamination: incorporation of hypoxanthine and xanthine into DNA and RNA caused by defects in purine nucleotide metabolism. Using Escherichia coli and Saccharomyces cerevisiae with defined mutations in purine metabolism in conjunction with analytical methods for quantifying deaminated nucleobases in DNA and RNA, we observed large increases (up to 600-fold) in hypoxanthine in both DNA and RNA in cells unable to convert IMP to XMP or AMP (IMP dehydrogenase, guaB; adenylosuccinate synthetase, purA, and ADE12), and unable to remove dITP/ITP and dXTP/XTP from the nucleotide pool (dITP/XTP pyrophosphohydrolase, rdgB and HAM1). Conversely, modest changes in xanthine levels were observed in RNA (but not DNA) from E. coli lacking purA and rdgB and the enzyme converting XMP to GMP (GMP synthetase, guaA). These observations suggest that disturbances in purine metabolism caused by known genetic polymorphisms could increase the burden of mutagenic deaminated nucleobases in DNA and interfere with gene expression and RNA function, a situation possibly exacerbated by the nitrosative stress of concurrent inflammation. The results also suggest a mechanistic basis for the pathophysiology of human inborn errors of purine nucleotide metabolism.