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Mouse RS21‐C6 is a mammalian 2′‐deoxycytidine 5′‐triphosphate pyrophosphohydrolase that prefers 5‐iodocytosine
Author(s) -
aka Mari,
Tsuchimoto Daisuke,
Sakumi Kunihiko,
Nakabeppu Yusaku
Publication year - 2009
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2009.06898.x
Subject(s) - nucleotide , biochemistry , nucleoside , dna , cytosine , biology , dna replication , nucleoside triphosphate , microbiology and biotechnology , chemistry , gene
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 k cat / K m (s −1 · m −1 ) values were 3.11 × 10 4 , 4.49 × 10 3 and 1.87 × 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.