Mouse RS21-C6 is a mammalian 2′-deoxycytidine 5′-triphosphate pyrophosphohydrolase that prefers 5-iodocytosine
Mouse RS21-C6 is a mammalian 2′-deoxycytidine 5′-triphosphate pyrophosphohydrolase that prefers 5-iodocytosine
复制标题
DOI：
10.1111/j.1742-4658.2009.06898.x
复制
发表时间：
2009-03-01
期刊：
影响因子：
5.4
通讯作者：
Nakabeppu, Yusaku
中科院分区：
文献类型：
--
作者：
Nonaka, Mari;Tsuchimoto, Daisuke;Nakabeppu, Yusaku
活细胞中的游离核苷酸在多种生物反应中发挥重要作用，并经常发生化学修饰。碱基的阳离子。由于修饰的核苷酸可能对细胞有有害影响，因此必须将其从细胞内核苷酸池中清除。由于ITP是最丰富的核苷酸ATP的脱氨产物，我们对ITP结合蛋白进行了筛选，并鉴定出RS21-C6蛋白，该蛋白不仅结合ITP，还结合ATP。纯化的重组RS21-C6将几种典型的三磷酸核苷水解为相应的单磷酸核苷。RS21-C6的焦磷酸水解酶活性显示出对三磷酸脱氧核苷和胞嘧啶碱基的偏好。dtp、dATP和dTTP的k(cat)/ k -m （s(-1). m -1）值分别为3.11 × 10(4)、4.49 × 10(3)和1.87 × 10(3)， RS21-C6不水解dGTP。在分析的碱基修饰的核苷酸中，5-I-dCTP显示的k(cat)/ k -m值比相应的未修饰的核苷酸dCTP高8倍。RS21-C6在增殖细胞和非增殖细胞中均有表达，并且定位于细胞质中。这些结果表明RS21-C6通过水解典型的dCTP产生dTTP从头合成的上游前体dCMP。此外，RS21-C6还可能通过水解修饰的dCTP来防止不适当的DNA甲基化、DNA复制阻断或诱变。
Free nucleotides in living cells play important roles in a variety of biological reactions, and often undergo chemical modi. cations of their base moieties. As modified nucleotides may have deleterious effects on cells, they must be eliminated from intracellular nucleotide pools. We have performed a screen for ITP-binding proteins because ITP is a deaminated product of ATP, the most abundant nucleotide, and identified RS21-C6 protein, which bound not only ITP but also ATP. Purified, recombinant RS21-C6 hydrolyzed several canonical nucleoside triphosphates to the corresponding nucleoside monophosphates. The pyrophosphohydrolase activity of RS21-C6 showed a preference for deoxynucleoside triphosphates and cytosine bases. The k(cat)/K-m (s(-1).M-1) values were 3.11 X 10(4), 4.49 x 10(3) and 1.87 x 10(3) for dCTP, dATP and dTTP, respectively, and RS21-C6 did not hydrolyze dGTP. Of the base-modified nucleotides analyzed, 5-I-dCTP showed an eightfold higher k(cat)/K-m value compared with that of its corresponding unmodified nucleotide, dCTP. RS21-C6 is expressed in both proliferating and non-proliferating cells, and is localized to the cytoplasm. These results show that RS21-C6 produces dCMP, an upstream precursor for the de novo synthesis of dTTP, by hydrolyzing canonical dCTP. Moreover, RS21-C6 may also prevent inappropriate DNA methylation, DNA replication blocking or mutagenesis by hydrolyzing modified dCTP.