tailieunhanh - Báo cáo khoa học: Mouse RS21-C6 is a mammalian 2¢-deoxycytidine 5¢-triphosphate pyrophosphohydrolase that prefers 5-iodocytosine

Free nucleotides in living cells play important roles in a variety of biolo-gical reactions, and often undergo chemical modifications of their base moieties. As modified nucleotides may have deleterious effects on cells, they must be eliminated from intracellular nucleotide pools. | ễFEBS Journal Mouse RS21-C6 is a mammalian 2 -deoxycytidine 5 -triphosphate pyrophosphohydrolase that prefers 5-iodocytosine Mari Nonaka Daisuke Tsuchimoto Kunihiko Sakumi and Yusaku Nakabeppu Division of NeurofunctionalGenomics Department of Immunobiology and Neuroscience Medical institute of Bioregulation Kyushu University Fukuoka Japan Keywords 5-I-dCTP CpG methylation dCTPase modified nucleotide nucleotide metabolism Correspondence D. Tsuchimoto Division of Neurofunctional Genomics Department of Immunobiology and Neuroscience Medical institute of Bioregulation Kyushu University Maidashi 3-1-1 Higashi-ku Fukuoka 812-8582 Japan Fax 81 92 642 6804 Tel 81 92 642 6802 E-mail daisuke@ Received 2 September 2008 revised 8 January 2009 accepted 12 January 2009 doi Free nucleotides in living cells play important roles in a variety of biological reactions and often undergo chemical modifications 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 kcat Km s-1 M-1 values were X 104 X 103 and X 103 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 kcat Km 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