Defects in purine nucleotide metabolism lead to substantial incorporation of xanthine and hypoxanthine into DNA and RNA.
نویسندگان
چکیده
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.
منابع مشابه
Purine metabolism in mesophyll protoplasts of tobacco (Nicotiana tabacum) leaves.
The overall metabolism of purines was studied in tobacco (Nicotiana tabacum) mesophyll protoplasts. Metabolic pathways were studied by measuring the conversion of radioactive adenine, adenosine, hypoxanthine and guanine into purine ribonucleotides, ribonucleosides, bases and nucleic acid constituents. Adenine was extensively deaminated to hypoxanthine, whereupon it was also converted into AMP a...
متن کاملRegulation of de novo purine synthesis in human bone marrow mononuclear cells by hypoxanthine.
In previous studies from this laboratory, human bone marrow hypoxanthine concentrations were found to average 7.1 microM, three times higher than plasma hypoxanthine concentrations measured simultaneously. To assess the significance of this finding, the relationship between hypoxanthine concentration and the rate of purine nucleotide synthesis by the de novo pathway was studied in normal human ...
متن کاملSeparate de Novo and Salvage Purine Pools Are Involved in the Biosynthesis of Theobromine but Not Caffeine in Leaves of Coffea arabica L.
In Coffea arabica leaves, the purine ring of theobromine (3,7-dimethylxanthine) and caffeine (1,3,7-trimethylxanthine) is provided by de novo purine biosynthesis: (a) [14C]glycine, [14C]bicarbonate, and [14C]formate were incorporated into inosine 5[prime]- monophosphate (IMP), sum of adenine nucleotides ([sigma]Ade), theobromine, and caffeine; and (b) incorporation of [14C]formate into IMP, [si...
متن کاملHypoxanthine incorporation is nonmutagenic in Escherichia coli.
Endonuclease V, encoded by the nfi gene, initiates removal of the base analogs hypoxanthine and xanthine from DNA, acting to prevent mutagenesis from purine base deamination within the DNA. On the other hand, the RdgB nucleotide hydrolase in Escherichia coli is proposed to prevent hypoxanthine and xanthine incorporation into DNA by intercepting the noncanonical DNA precursors dITP and dXTP. Bec...
متن کاملPurine salvage networks in Giardia lamblia
Purine metabolism in Giardia lamblia was investigated by monitoring incorporation of radiolabeled precursors into purine nucleotides in the log-phase trophozoites cultivated in vitro in axenic media and incubated in buffered saline glucose. The lack of incorporation of formate, glycine, hypoxanthine, inosine, and xanthine into the nucleotide pool suggests the absence of de novo purine nucleotid...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Proceedings of the National Academy of Sciences of the United States of America
دوره 109 7 شماره
صفحات -
تاریخ انتشار 2012