Peptide name : Oxidized purine nucleoside triphosphate hydrolase

Source/Organism : Human

Linear/Cyclic : Not found

Chirality : Not found

Peptide length: 156

C-terminal modification: Not found

N-terminal modification : Not found

Non-natural peptide information: None

Assay type : Antibody-based assay

Assay time : 48h

Activity : Not found

Cell line : HEK293

Cancer type : Not specified

Other activity : Not found

Amino acid composition bar chart :

Molecular mass : 17951.2892 Dalton

Aliphatic index : 0.792

Instability index : 42.2955

Hydrophobicity (GRAVY) : -0.335

Isoelectric point : 4.9497

Charge (pH 7) : -7.2238

Aromaticity : 0.121

Molar extinction coefficient (cysteine, cystine): (27960, 28085)

Hydrophobic/hydrophilic ratio : 1.13698630

hydrophobic moment : -0.090

Missing amino acid : None

Most occurring amino acid : G

Most occurring amino acid frequency : 16

Least occurring amino acid : N

Least occurring amino acid frequency : 1

Secondary structure fraction (Helix, Turn, Sheet): (0.2, 0.2, 0.3)

SMILES Notation: CC[C@H](C)[C@H](NC(=O)[C@H](CO)NC(=O)[C@H](CC(=O)O)NC(=O)[C@@H](NC(=O)[C@H](CS)NC(=O)[C@H](Cc1ccccc1)NC(=O)[C@@H](NC(=O)[C@H](Cc1c[nH]cn1)NC(=O)[C@@H](NC(=O)[C@H](CC(=O)O)NC(=O)[C@H](CCSC)NC(=O)[C@H](CC(C)C)NC(=O)[C@H](CCC(=O)O)NC(=O)[C@@H]1CCCN1C(=O)[C@H](CCC(=O)O)NC(=O)CNC(=O)[C@@H](NC(=O)[C@H](Cc1ccccc1)NC(=O)[C@H](CCC(=O)O)NC(=O)[C@H](Cc1ccccc1)NC(=O)[C@@H](NC(=O)[C@@H](NC(=O)[C@H](CCC(N)=O)NC(=O)CNC(=O)[C@@H](NC(=O)[C@H](CCCCN)NC(=O)[C@H](Cc1c[nH]cn1)NC(=O)[C@H](CC(C)C)NC(=O)[C@H](C)NC(=O)[C@H](CC(=O)O)NC(=O)[C@@H](NC(=O)[C@@H](NC(=O)[C@H](CC(C)C)NC(=O)CNC(=O)[C@H](CO)NC(=O)[C@H](CCC(=O)O)NC(=O)[C@H](CCC(=O)O)NC(=O)[C@H](CCC(N)=O)NC(=O)[C@H](CC(C)C)NC(=O)[C@H](CCC(=O)O)NC(=O)[C@H](CCCNC(=N)N)NC(=O)[C@H](CCCNC(=N)N)NC(=O)[C@H](C)NC(=O)CNC(=O)[C@H](CC(=O)O)NC(=O)[C@H](CCC(=O)O)NC(=O)[C@@H](NC(=O)[C@@H](NC(=O)[C@H](CCC(=O)O)NC(=O)CNC(=O)[C@H](CCC(=O)O)NC(=O)[C@H](CCC(N)=O)NC(=O)[C@@H](NC(=O)[C@H](CCCCN)NC(=O)CNC(=O)CNC(=O)[C@H](Cc1ccccc1)NC(=O)CNC(=O)[C@H](CC(N)=O)NC(=O)[C@H](Cc1c[nH]c2ccccc12)NC(=O)[C@H](CCCNC(=N)N)NC(=O)CNC(=O)[C@H](C)NC(=O)CNC(=O)[C@H](Cc1ccccc1)NC(=O)CNC(=O)[C@H](CCCNC(=N)N)NC(=O)[C@H](CCCCN)NC(=O)[C@H](CCCCN)NC(=O)[C@H](CCSC)NC(=O)CNC(=O)[C@H](CC(C)C)NC(=O)[C@H](CC(C)C)NC(=O)[C@@H](NC(=O)[C@H](CCCNC(=N)N)NC(=O)[C@H](CCC(N)=O)NC(=O)[C@@H]1CCCN1C(=O)[C@H](CCC(N)=O)NC(=O)[C@H](CC(C)C)NC(=O)[C@@H](NC(=O)[C@H](CC(C)C)NC(=O)[C@@H](NC(=O)[C@H](CC(C)C)NC(=O)[C@@H](NC(=O)[C@H](Cc1ccc(O)cc1)NC(=O)[C@H](CC(C)C)NC(=O)[C@H](CCCNC(=N)N)NC(=O)[C@H](CO)NC(=O)[C@H](C)NC(=O)CNC(=O)[C@@H](N)CCSC)[C@@H](C)O)C(C)C)C(C)C)C(C)C)C(C)C)[C@@H](C)O)[C@@H](C)CC)[C@@H](C)O)C(C)C)C(C)C)[C@@H](C)CC)C(C)C)C(C)C)C(C)C)C(C)C)[C@@H](C)O)C(=O)N[C@@H](CCC(N)=O)C(=O)NCC(=O)N[C@H](C(=O)N1CCC[C@H]1C(=O)N[C@H](C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@@H](CO)C(=O)N[C@@H](CC(=O)O)C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@@H](CCSC)C(=O)N[C@@H](CCCNC(=N)N)C(=O)N1CCC[C@H]1C(=O)N[C@@H](CS)C(=O)N[C@@H](Cc1c[nH]c2ccccc12)C(=O)N[C@@H](Cc1ccccc1)C(=O)N[C@@H](CCC(N)=O)C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CC(=O)O)C(=O)N[C@@H](CCC(N)=O)C(=O)N[C@H](C(=O)N1CCC[C@H]1C(=O)N[C@@H](Cc1ccccc1)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CC(=O)O)C(=O)N[C@@H](CCSC)C(=O)N[C@@H](Cc1c[nH]c2ccccc12)C(=O)N1CCC[C@H]1C(=O)N[C@@H](CC(=O)O)C(=O)N[C@@H](CC(=O)O)C(=O)N[C@@H](CO)C(=O)N[C@@H](Cc1ccc(O)cc1)C(=O)N[C@@H](Cc1c[nH]c2ccccc12)C(=O)N[C@@H](Cc1ccccc1)C(=O)N1CCC[C@H]1C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CCC(N)=O)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](Cc1ccccc1)C(=O)N[C@@H](Cc1c[nH]cn1)C(=O)NCC(=O)N[C@@H](Cc1ccc(O)cc1)C(=O)N[C@@H](Cc1ccccc1)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](Cc1ccccc1)C(=O)N[C@@H](CCC(N)=O)C(=O)NCC(=O)N[C@@H](CCC(N)=O)C(=O)N[C@@H](CC(=O)O)C(=O)N[C@H](C(=O)N[C@H](C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CC(=O)O)C(=O)N[C@@H](Cc1ccc(O)cc1)C(=O)N[C@H](C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CCCNC(=N)N)C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@H](C(=O)N[C@@H](CC(=O)O)C(=O)N[C@H](C(=O)N[C@H](C(=O)O)C(C)C)[C@@H](C)O)C(C)C)[C@@H](C)O)[C@@H](C)CC)[C@@H](C)O)[C@@H](C)CC)C(C)C)[C@@H](C)O

1 : Kang D, et al. Intracellular localization of 8-oxo-dGTPase in human cells, with special reference to the role of the enzyme in mitochondria. J Biol Chem. 1995; 270:14659-65. doi: 10.1074/jbc.270.24.14659

2 : Sakumi K, et al. Cloning and expression of cDNA for a human enzyme that hydrolyzes 8-oxo-dGTP, a mutagenic substrate for DNA synthesis. J Biol Chem. 1993; 268:23524-30.

3 : Nakamura T, et al. Crystallization and preliminary X-ray analysis of human MTH1 complexed with two oxidized nucleotides, 8-oxo-dGMP and 2-oxo-dATP. Acta Crystallogr Sect F Struct Biol Cryst Commun. 2006; 62:1283-5. doi: 10.1107/S1744309106049529

4 : Oda H, et al. Regulation of expression of the human MTH1 gene encoding 8-oxo-dGTPase. Alternative splicing of transcription products. J Biol Chem. 1997; 272:17843-50. doi: 10.1074/jbc.272.28.17843

5 : Fujikawa K, et al. Human MTH1 protein hydrolyzes the oxidized ribonucleotide, 2-hydroxy-ATP. Nucleic Acids Res. 2001; 29:449-54. doi: 10.1093/nar/29.2.449

6 : Oda H, et al. Multi-forms of human MTH1 polypeptides produced by alternative translation initiation and single nucleotide polymorphism. Nucleic Acids Res. 1999; 27:4335-43. doi: 10.1093/nar/27.22.4335

7 : Ellermann M, et al. Novel Class of Potent and Cellularly Active Inhibitors Devalidates MTH1 as Broad-Spectrum Cancer Target. ACS Chem Biol. 2017; 12:1986-1992. doi: 10.1021/acschembio.7b00370

8 : Carter M, et al. Crystal structure, biochemical and cellular activities demonstrate separate functions of MTH1 and MTH2. Nat Commun. 2015; 6:7871. doi: 10.1038/ncomms8871

9 : Burkard TR, et al. Initial characterization of the human central proteome. BMC Syst Biol. 2011; 5:17. doi: 10.1186/1752-0509-5-17

10 : Takagi Y, et al. Human MTH3 (NUDT18) protein hydrolyzes oxidized forms of guanosine and deoxyguanosine diphosphates: comparison with MTH1 and MTH2. J Biol Chem. 2012; 287:21541-9. doi: 10.1074/jbc.M112.363010

11 : Miyako K, et al. Association study of human MTH1 gene polymorphisms with type 1 diabetes mellitus. Endocr J. 2004; 51:493-8. doi: 10.1507/endocrj.51.493

12 : Huber KV, et al. Stereospecific targeting of MTH1 by (S)-crizotinib as an anticancer strategy. Nature. 2014; 508:222-7. doi: 10.1038/nature13194

13 : Furuichi M, et al. Genomic structure and chromosome location of the human mutT homologue gene MTH1 encoding 8-oxo-dGTPase for prevention of A:T to C:G transversion. Genomics. 1994; 24:485-90. doi: 10.1006/geno.1994.1657

14 : Mishima M, et al. Structure of human MTH1, a Nudix family hydrolase that selectively degrades oxidized purine nucleoside triphosphates. J Biol Chem. 2004; 279:33806-15. doi: 10.1074/jbc.M402393200

15 : Fujii Y, et al. Functional significance of the conserved residues for the 23-residue module among MTH1 and MutT family proteins. J Biol Chem. 1999; 274:38251-9. doi: 10.1074/jbc.274.53.38251

16 : Hillier LW, et al. The DNA sequence of human chromosome 7. Nature. 2003; 424:157-64. doi: 10.1038/nature01782

17 : Scherer SW, et al. Human chromosome 7: DNA sequence and biology. Science. 2003; 300:767-72. doi: 10.1126/science.1083423

18 : Sakai Y, et al. The GT to GC single nucleotide polymorphism at the beginning of an alternative exon 2C of human MTH1 gene confers an amino terminal extension that functions as a mitochondrial targeting signal. J Mol Med (Berl). 2006; 84:660-70. doi: 10.1007/s00109-006-0053-5

19 : Scaletti ER, et al. MutT homologue 1 (MTH1) removes N6-methyl-dATP from the dNTP pool. J Biol Chem. 2020; 295:4761-4772. doi: 10.1074/jbc.RA120.012636

20 : Jemth AS, et al. MutT homologue 1 (MTH1) catalyzes the hydrolysis of mutagenic O6-methyl-dGTP. Nucleic Acids Res. 2018; 46:10888-10904. doi: 10.1093/nar/gky896

21 : Nissink JW, et al. MTH1 Substrate Recognition--An Example of Specific Promiscuity. PLoS One. 2016; 11:e0151154. doi: 10.1371/journal.pone.0151154

22 : Kwon O, et al. NF-kappaB inhibition increases chemosensitivity to trichostatin A-induced cell death of Ki-Ras-transformed human prostate epithelial cells. Carcinogenesis. 2006; 27:2258-68. doi: 10.1093/carcin/bgl097

23 : Gerhard DS, et al. The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). Genome Res. 2004; 14:2121-7. doi: 10.1101/gr.2596504

24 : Gad H, et al. MTH1 inhibition eradicates cancer by preventing sanitation of the dNTP pool. Nature. 2014; 508:215-21. doi: 10.1038/nature13181

25 : Yoshimura D, et al. An oxidized purine nucleoside triphosphatase, MTH1, suppresses cell death caused by oxidative stress. J Biol Chem. 2003; 278:37965-73. doi: 10.1074/jbc.M306201200

26 : Waz S, et al. Structural and Kinetic Studies of the Human Nudix Hydrolase MTH1 Reveal the Mechanism for Its Broad Substrate Specificity. J Biol Chem. 2017; 292:2785-2794. doi: 10.1074/jbc.M116.749713

27 : Svensson LM, et al. Crystal structure of human MTH1 and the 8-oxo-dGMP product complex. FEBS Lett. 2011; 585:2617-21. doi: 10.1016/j.febslet.2011.07.017

28 : Fujikawa K, et al. The oxidized forms of dATP are substrates for the human MutT homologue, the hMTH1 protein. J Biol Chem. 1999; 274:18201-5. doi: 10.1074/jbc.274.26.18201

29 : Sakai Y, et al. A molecular basis for the selective recognition of 2-hydroxy-dATP and 8-oxo-dGTP by human MTH1. J Biol Chem. 2002; 277:8579-87. doi: 10.1074/jbc.M110566200

Paper title : Intracellular localization of 8-oxo-dGTPase in human cells, with special reference to the role of the enzyme in mitochondria.

Doi : https://doi.org/10.1074/jbc.270.24.14659

Abstract : We examined the intracellular distribution of 8-oxo-dGTPase (8-oxo-7,8-dihydrodeoxyguanosine triphosphatase) encoded by the MTH1 gene, a human mutator homologue. The activity of 8-oxo-dGTPase mainly located in cytosolic and mitochondrial soluble fractions of Jurkat cells, a human T-cell leukemia line. Electron microscopic immunocytochemistry, using a specific antibody against MTH1 protein, showed localization of MTH1 protein in the mitochondrial matrix. Activity in the mitochondria accounted for about 4% of the total activity. The specific activity in the mitochondrial soluble fraction (8093 units/mg protein) was as high as that in the cytosolic fraction (8111 unit/mg protein). The 8-oxo-dGTPase activities in cytosolic and mitochondrial soluble fractions co-eluted with MTH1 protein by anion-exchange chromatography, and the molecular mass of the mitochondrial MTH1 protein was much the same as that of the cytosolic MTH1 protein (about 18 kDa). HeLa cells expressing MTH1 cDNA showed an increased cytoplasmic signal together with a weak signal in the nucleus in in situ immunostaining of MTH1 protein, and the overexpressed MTH1 protein was recovered from both cytosolic and mitochondrial fractions. Thus, the 8-oxo-dGTPase encoded by MTH1 gene is localized in mitochondrial and cytosol.

Paper title : Cloning and expression of cDNA for a human enzyme that hydrolyzes 8-oxo-dGTP, a mutagenic substrate for DNA synthesis.

Doi : https://doi.org/Not available

Abstract : 8-Oxoguanine (8-oxo-7, 8-dihydroguanine) is produced in DNA, as well as in nucleotide pools of cells, by active oxygen species normally formed during cellular metabolic processes. 8-Oxoguanine nucleotide can pair with cytosine and adenine nucleotides at almost equal efficiencies, and transversion mutation ensues. Human cells contain enzyme activity, which hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP, and this enzyme is responsible for preventing misincorporation of 8-oxoguanine into DNA. We purified this particular human enzyme to physical homogeneity and determined a partial amino acid sequence. We then cloned the cDNA for human 8-oxo-dGTPase and examined its nucleotide sequence. The human protein comprises 156 amino acid residues and has some sequence homology with the Escherichia coli MutT protein, which has a distinct 8-oxo-dGTPase activity. When the human cDNA was expressed in E. coli mutT- mutant cells, there was a significant amount of 8-oxo-dGTPase activity. In such cells, the frequency of spontaneous mutation was greatly reduced. We propose that the human 8-oxo-dGTPase protects genetic information from the untoward effects of endogenous oxygen radicals.

Paper title : Crystallization and preliminary X-ray analysis of human MTH1 complexed with two oxidized nucleotides, 8-oxo-dGMP and 2-oxo-dATP.

Doi : https://doi.org/10.1107/S1744309106049529

Abstract : Human MutT homologue 1 (hMTH1) hydrolyzes a variety of oxidized purine nucleoside triphosphates, including 8-oxo-dGTP, 2-oxo-dATP, 2-oxo-ATP and 8-oxo-dATP, to their corresponding nucleoside monophosphates, while Escherichia coli MutT possesses prominent substrate specificity for 8-oxoguanine nucleotides. Three types of crystals were obtained corresponding to the following complexes: selenomethionine-labelled hMTH1 with 8-oxo-dGMP (SeMet hMTH1-8-oxo-dGMP), hMTH1 with 8-oxo-dGMP (hMTH1-8-oxo-dGMP) and hMTH1 with 2-oxo-dATP (hMTH1-2-oxo-dATP). Crystals of the SeMet hMTH1-8-oxo-dGMP complex belong to space group P4(1)2(1)2, with unit-cell parameters a = b = 45.8, c = 153.6 A, and diffracted to 2.90 A. Crystals of hMTH1-8-oxo-dGMP and hMTH1-2-oxo-dATP belong to space groups P2(1) and P2(1)2(1)2(1), with unit-cell parameters a = 34.0, b = 59.0, c = 65.9 A, beta = 90.7 degrees and a = 59.2, b = 67.3, c = 80.0 A, respectively. Their diffraction data were collected at resolutions of 1.95 and 2.22 A, respectively.

Paper title : Regulation of expression of the human MTH1 gene encoding 8-oxo-dGTPase. Alternative splicing of transcription products.

Doi : https://doi.org/10.1074/jbc.272.28.17843

Abstract : The enzyme 8-oxo-7,8-dihydrodeoxyguanosine triphosphatase (8-oxo-dGTPase) hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP, thereby preventing misincorporation of 8-oxo-dGTP into DNA. We investigated expression of MTH1 gene encoding 8-oxo-dGTPase. Large amounts of MTH1 mRNA were present in thymus and testis, embryonic tissues, and certain cell lines. In peripheral blood lymphocytes, the level of MTH1 mRNA was significantly increased after concomitant treatment with phytohemagglutinin and interleukin-2. Analyses of the 5' regions of the MTH1 transcripts revealed that 7 types of MTH1 mRNAs, which may be produced by transcription initiation at different sites and/or alternative splicing. The MTH1 gene consists of 5 major exons, some of which are composed of differentially processed segments. All types of MTH1 mRNAs carry the entire coding region, and may be functional. Three ATG initiation codons in-frame were found in the 5' regions of some of the MTH1 mRNAs. There is a polymorphic alteration at the 5' splicing site (GT to GC) located in exon 2, an event which affects splicing patterns of the MTH1 transcript. Allele frequency of this polymorphism is about 20% among healthy volunteers.

Paper title : Human MTH1 protein hydrolyzes the oxidized ribonucleotide, 2-hydroxy-ATP.

Doi : https://doi.org/10.1093/nar/29.2.449

Abstract : The human nucleotide pool sanitization enzyme, MTH1, hydrolyzes 2-hydroxy-dATP and 8-hydroxy-dATP in addition to 8-hydroxy-dGTP. We report here that human MTH1 is highly specific for 2-hydroxy-ATP, among the cognate ribonucleoside triphosphates. The pyrophosphatase activities for 8-hydroxy-GTP, 2-hydroxy-ATP and 8-hydroxy-ATP were measured by high-performance liquid chromatography. The kinetic parameters thus obtained indicate that the catalytic efficiencies of MTH1 are in the order of 2-hydroxy-dATP > 2-hydroxy-ATP > 8-hydroxy-dGTP > 8-hydroxy-dATP >> dGTP > 8-hydroxy-GTP > 8-hydroxy-ATP. Notably, MTH1 had the highest affinity for 2-hydroxy-ATP among the known substrates. ATP is involved in energy metabolism and signal transduction, and is a precursor in RNA synthesis. We suggest that the 2-hydroxy-ATP hydrolyzing activity of MTH1 might prevent the perturbation of these ATP-related pathways by the oxidized ATP.

Paper title : Multi-forms of human MTH1 polypeptides produced by alternative translation initiation and single nucleotide polymorphism.

Doi : https://doi.org/10.1093/nar/27.22.4335

Abstract : The human MTH1 gene for 8-oxo-7,8-dihydrodeoxyguanosine triphosphatase, produces seven types (types 1, 2A, 2B, 3A, 3B, 4A and 4B) of mRNAs. The B-type mRNAs with exon 2b-2c segments have three additional in-frame AUGs in their 5' regions. We report here that these transcripts produce three forms of MTH1 polypeptides (p22, p21 and p18) in in vitro translation reactions. Three polypeptides were also detected in extracts of human cells, using western blotting. B-type mRNAs with a polymorphic alteration (GU-->GC) at the beginning of exon 2c that converts an in-frame UGA to CGA yielding another in-frame AUG further upstream, produced an additional polypeptide (p26) in vitro. Substitution of each AUG abolished the production of each corresponding polypeptide. Cell lines from individuals with the GC allele contain more B-type mRNAs than do those of GT homozygotes, and the former produce all of four polypeptides but the latter lack p26. Amounts of each polypeptide reflected copy number of the GC allele in each cell line. There is an apparent linkage dis-equilibrium between the two polymorphic sites, GT/GC at exon 2c and Val83/Met83 at codon 83 for p18.

Paper title : Novel Class of Potent and Cellularly Active Inhibitors Devalidates MTH1 as Broad-Spectrum Cancer Target.

Doi : https://doi.org/10.1021/acschembio.7b00370

Abstract : MTH1 is a hydrolase responsible for sanitization of oxidized purine nucleoside triphosphates to prevent their incorporation into replicating DNA. Early tool compounds published in the literature inhibited the enzymatic activity of MTH1 and subsequently induced cancer cell death; however recent studies have questioned the reported link between these two events. Therefore, it is important to validate MTH1 as a cancer dependency with high quality chemical probes. Here, we present BAY-707, a substrate-competitive, highly potent and selective inhibitor of MTH1, chemically distinct compared to those previously published. Despite superior cellular target engagement and pharmacokinetic properties, inhibition of MTH1 with BAY-707 resulted in a clear lack of in vitro or in vivo anticancer efficacy either in mono- or in combination therapies. Therefore, we conclude that MTH1 is dispensable for cancer cell survival.

Paper title : Crystal structure, biochemical and cellular activities demonstrate separate functions of MTH1 and MTH2.

Doi : https://doi.org/10.1038/ncomms8871

Abstract : Deregulated redox metabolism in cancer leads to oxidative damage to cellular components including deoxyribonucleoside triphosphates (dNTPs). Targeting dNTP pool sanitizing enzymes, such as MTH1, is a highly promising anticancer strategy. The MTH2 protein, known as NUDT15, is described as the second human homologue of bacterial MutT with 8-oxo-dGTPase activity. We present the first NUDT15 crystal structure and demonstrate that NUDT15 prefers other nucleotide substrates over 8-oxo-dGTP. Key structural features are identified that explain different substrate preferences for NUDT15 and MTH1. We find that depletion of NUDT15 has no effect on incorporation of 8-oxo-dGTP into DNA and does not impact cancer cell survival in cell lines tested. NUDT17 and NUDT18 were also profiled and found to have far less activity than MTH1 against oxidized nucleotides. We show that NUDT15 is not a biologically relevant 8-oxo-dGTPase, and that MTH1 is the most prominent sanitizer of the cellular dNTP pool known to date.

Paper title : Initial characterization of the human central proteome.

Doi : https://doi.org/10.1186/1752-0509-5-17

Abstract : BACKGROUND: On the basis of large proteomics datasets measured from seven human cell lines we consider their intersection as an approximation of the human central proteome, which is the set of proteins ubiquitously expressed in all human cells. Composition and properties of the central proteome are investigated through bioinformatics analyses. RESULTS: We experimentally identify a central proteome comprising 1,124 proteins that are ubiquitously and abundantly expressed in human cells using state of the art mass spectrometry and protein identification bioinformatics. The main represented functions are proteostasis, primary metabolism and proliferation. We further characterize the central proteome considering gene structures, conservation, interaction networks, pathways, drug targets, and coordination of biological processes. Among other new findings, we show that the central proteome is encoded by exon-rich genes, indicating an increased regulatory flexibility through alternative splicing to adapt to multiple environments, and that the protein interaction network linking the central proteome is very efficient for synchronizing translation with other biological processes. Surprisingly, at least 10% of the central proteome has no or very limited functional annotation. CONCLUSIONS: Our data and analysis provide a new and deeper description of the human central proteome compared to previous results thereby extending and complementing our knowledge of commonly expressed human proteins. All the data are made publicly available to help other researchers who, for instance, need to compare or link focused datasets to a common background.

Paper title : Human MTH3 (NUDT18) protein hydrolyzes oxidized forms of guanosine and deoxyguanosine diphosphates: comparison with MTH1 and MTH2.

Doi : https://doi.org/10.1074/jbc.M112.363010

Abstract : Most of the proteins carrying the 23-residue MutT-related sequence are capable of hydrolyzing compounds with a general structure of nucleoside diphosphate linked to another moiety X and are called the Nudix hydrolases. Among the 22 human Nudix proteins (identified by the sequence signature), some remain uncharacterized as enzymes without a defined substrate. Here, we reveal that the NUDT18 protein, whose substrate was unknown, can degrade 8-oxo-7,8-dihydroguanine (8-oxo-Gua)-containing nucleoside diphosphates to the monophosphates. Because this enzyme is closely related to MTH1 (NUDT1) and MTH2 (NUDT15), we propose that it should be named MTH3. Although these three human proteins resemble each other in their sequences, their substrate specificities differ considerably. MTH1 cleaves 8-oxo-dGTP but not 8-oxo-dGDP, whereas MTH2 can degrade both 8-oxo-dGTP and 8-oxo-dGDP, although the intrinsic enzyme activity of MTH2 is considerably lower than that of MTH1. On the other hand, MTH3 is specifically active against 8-oxo-dGDP and hardly cleaves 8-oxo-dGTP. Other types of oxidized nucleoside diphosphates, 2-hydroxy-dADP and 8-hydroxy-dADP, were also hydrolyzed by MTH3. Another notable feature of the MTH3 enzyme is its action toward the ribonucleotide counterpart. MTH3 can degrade 8-oxo-GDP as efficiently as 8-oxo-dGDP, which is in contrast to the finding that MTH1 and MTH2 show a limited activity against the ribonucleotide counterpart, 8-oxo-GTP. These three enzymes may function together to help maintain the high fidelity of DNA replication and transcription under oxidative stress.

Paper title : Association study of human MTH1 gene polymorphisms with type 1 diabetes mellitus.

Doi : https://doi.org/10.1507/endocrj.51.493

Abstract : Reactive oxygen species are considered to play a role in the development of diabetes mellitus and its complications. Human MTH1 (mutT homologue 1) has 8-oxo-7,8-dihydrodeoxyguanosine triphosphatase activity, which repairs oxidized forms of dGTP. This enzyme is known to have a thermolabile Met83 variant. We examined whether Val83Met polymorphism of human MTH1 gene is associated with type 1 diabetes mellitus. We recruited 156 type 1 diabetic patients (59 males and 97 females). The polymorphism was analyzed by restriction fragment length polymorphism analysis with Nsi I. The Met/Met genotype at codon 83 was very rare in both control and patient groups. Val/Met genotype tended to be more frequent in the whole type 1 diabetic patients than in controls. When subjects were divided into subgroups according to gender, there were no differences in the genotype and allele frequencies between patients and controls in males. On the other hand, in female type 1 diabetic patients, the Val/Met genotype was more frequent than in female controls (corrected P = 0.102). The Met allele was significantly more frequent in female type 1 diabetic patients than in female controls (corrected P = 0.022). Our results suggested that the Met allele at codon 83 of MTH1 gene might be involved in the development of type 1 diabetes mellitus in the Japanese female population.

Paper title : Stereospecific targeting of MTH1 by (S)-crizotinib as an anticancer strategy.

Doi : https://doi.org/10.1038/nature13194

Abstract : Activated RAS GTPase signalling is a critical driver of oncogenic transformation and malignant disease. Cellular models of RAS-dependent cancers have been used to identify experimental small molecules, such as SCH51344, but their molecular mechanism of action remains generally unknown. Here, using a chemical proteomic approach, we identify the target of SCH51344 as the human mutT homologue MTH1 (also known as NUDT1), a nucleotide pool sanitizing enzyme. Loss-of-function of MTH1 impaired growth of KRAS tumour cells, whereas MTH1 overexpression mitigated sensitivity towards SCH51344. Searching for more drug-like inhibitors, we identified the kinase inhibitor crizotinib as a nanomolar suppressor of MTH1 activity. Surprisingly, the clinically used (R)-enantiomer of the drug was inactive, whereas the (S)-enantiomer selectively inhibited MTH1 catalytic activity. Enzymatic assays, chemical proteomic profiling, kinome-wide activity surveys and MTH1 co-crystal structures of both enantiomers provide a rationale for this remarkable stereospecificity. Disruption of nucleotide pool homeostasis via MTH1 inhibition by (S)-crizotinib induced an increase in DNA single-strand breaks, activated DNA repair in human colon carcinoma cells, and effectively suppressed tumour growth in animal models. Our results propose (S)-crizotinib as an attractive chemical entity for further pre-clinical evaluation, and small-molecule inhibitors of MTH1 in general as a promising novel class of anticancer agents.

Paper title : Genomic structure and chromosome location of the human mutT homologue gene MTH1 encoding 8-oxo-dGTPase for prevention of A:T to C:G transversion.

Doi : https://doi.org/10.1006/geno.1994.1657

Abstract : 8-Oxo-dGTP (8-oxo-7,8-dihydrodeoxyguanosine triphosphate) is produced by active oxygen species in the nucleotide pool of the cell and can be incorporated into cellular DNA. Human cells contain enzyme activity that hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP, thereby preventing occurrence of mutations, caused by misincorporation. When the cDNA for human 8-oxo-dGTPase was expressed in Escherichia coli mutT- mutant cells devoid of self 8-oxo-dGTPase activity, the elevated level of spontaneous A:T to C:G mutation frequency reverted to normal. We isolated the genomic sequence encoding the enzyme and named the gene MTH1 (for mutT human homologue). This gene is composed of at least 4 exons, spans approximately 9 kb, and is located on human chromosome 7p22.

Paper title : Structure of human MTH1, a Nudix family hydrolase that selectively degrades oxidized purine nucleoside triphosphates.

Doi : https://doi.org/10.1074/jbc.M402393200

Abstract : Oxygen radicals generated through normal cellular respiration processes can cause mutations in genomic and mitochondrial DNA. Human MTH1 hydrolyzes oxidized purine nucleoside triphosphates, such as 8-oxo-dGTP and 2-hydroxy-dATP, to monophosphates, thereby preventing the misincorporation of these oxidized nucleotides during replication. Here we present the solution structure of MTH1 solved by multidimensional heteronuclear NMR spectroscopy. The protein adopts a fold similar to that of Escherichia coli MutT, despite the low sequence similarity between these proteins outside the conserved Nudix motif. The substrate-binding pocket of MTH1, deduced from chemical shift perturbation experiments, is located at essentially the same position as in MutT; however, a pocket-forming helix is largely displaced in MTH1 (approximately 9 A) such that the shape of the pocket differs between the two proteins. Detailed analysis of the pocket-forming residues enabled us to identify Asn33 as one of the key residues in MTH1 for discriminating the oxidized form of purine, and mutation of this residue modifies the substrate specificity. We also show that MTH1 catalyzes hydrolysis of 8-oxo-dGTP through nucleophilic substitution of water at the beta-phosphate.

Paper title : Functional significance of the conserved residues for the 23-residue module among MTH1 and MutT family proteins.

Doi : https://doi.org/10.1074/jbc.274.53.38251

Abstract : Human MTH1 and Escherichia coli MutT proteins hydrolyze 7, 8-dihydro-8-oxo-dGTP (8-oxo-dGTP) to monophosphate, thus avoiding the incorporation of 8-oxo-7,8-dihydroguanine into nascent DNA. Although only 30 amino acid residues (23%) are identical between MTH1 and MutT, there is a highly conserved region consisting of 23 residues (MTH1, Gly(36)-Gly(58)) with 14 identical residues. A chimeric protein MTH1-Ec, in which the 23-residue sequence of MTH1 was replaced with that of MutT, retains its capability to hydrolyze 8-oxo-dGTP, thereby indicating that the 23-residue sequences of MTH1 and MutT are functionally and structurally equivalent and constitute functional modules. By saturation mutagenesis of the module in MTH1, 14 of the 23 residues proved to be essential to exert 8-oxo-dGTPase activity. For the other 9 residues (40, 42, 44, 46, 47, 49, 50, 54, and 58), positive mutants were obtained, and Arg(50) can be replaced with hydrophobic residues (Val, Leu, or Ile), with a greater stability and higher specific activity of the enzyme. Indispensabilities of Val(39), Ile(45), and Leu(53) indicate that an amphipathic property of alpha-helix I consisting of 14 residues of the module (Thr(44)-Gly(58)) is essential to maintain the stable catalytic surface for 8-oxo-dGTPase.

Paper title : The DNA sequence of human chromosome 7.

Doi : https://doi.org/10.1038/nature01782

Abstract : Human chromosome 7 has historically received prominent attention in the human genetics community, primarily related to the search for the cystic fibrosis gene and the frequent cytogenetic changes associated with various forms of cancer. Here we present more than 153 million base pairs representing 99.4% of the euchromatic sequence of chromosome 7, the first metacentric chromosome completed so far. The sequence has excellent concordance with previously established physical and genetic maps, and it exhibits an unusual amount of segmentally duplicated sequence (8.2%), with marked differences between the two arms. Our initial analyses have identified 1,150 protein-coding genes, 605 of which have been confirmed by complementary DNA sequences, and an additional 941 pseudogenes. Of genes confirmed by transcript sequences, some are polymorphic for mutations that disrupt the reading frame.

Paper title : Human chromosome 7: DNA sequence and biology.

Doi : https://doi.org/10.1126/science.1083423

Abstract : DNA sequence and annotation of the entire human chromosome 7, encompassing nearly 158 million nucleotides of DNA and 1917 gene structures, are presented. To generate a higher order description, additional structural features such as imprinted genes, fragile sites, and segmental duplications were integrated at the level of the DNA sequence with medical genetic data, including 440 chromosome rearrangement breakpoints associated with disease. This approach enabled the discovery of candidate genes for developmental diseases including autism.

Paper title : The GT to GC single nucleotide polymorphism at the beginning of an alternative exon 2C of human MTH1 gene confers an amino terminal extension that functions as a mitochondrial targeting signal.

Doi : https://doi.org/10.1007/s00109-006-0053-5

Abstract : Human MTH1 protein hydrolyzes oxidized purine nucleotides 8-oxo-2'-deoxyguanosine triphosphate (8-oxo-dGTP), 2-OH-dATP or their ribo-forms to their monophosphates, thus minimizing replicational and transcriptional errors both in the nuclei and mitochondria. MTH1 suppresses mitochondrial dysfunction and cell death caused by H(2)O(2). Furthermore, MTH1 suppresses the transient increase in 8-oxoguanine in mitochondrial DNA in the dopaminergic nerve terminals in mouse striatum after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine administration, and it protects the nerve terminals. We previously reported that a novel MTH1 allele with a single nucleotide polymorphism (SNP) in its exon 2c segment encodes the fourth MTH1 isoform, namely, MTH1a (p26), in addition to the three known isoforms, MTH1b (p22), c (p21), and d (p18). Another SNP located in exon 4 of the MTH1 gene, which is closely linked to the SNP in exon 2c, substitutes the Val83 residue in MTH1d with Met83. We herein show that all MTH1 isoforms efficiently hydrolyzed 2-OH-dATP and 8-oxo-dGTP. The amino terminal region of MTH1a functioned as a mitochondrial targeting signal when it was expressed in the HeLa cells as a fusion protein with enhanced green fluorescent protein. The cellular fractionation revealed that MTH1a(Met83) was localized in the mitochondria to the same extent as was MTH1d(Val83). However, the mitochondrial translocation of MTH1d(Met83) was less efficient than that of MTH1d(Val83).

Paper title : MutT homologue 1 (MTH1) removes N6-methyl-dATP from the dNTP pool.

Doi : https://doi.org/10.1074/jbc.RA120.012636

Abstract : MutT homologue 1 (MTH1) removes oxidized nucleotides from the nucleotide pool and thereby prevents their incorporation into the genome and thereby reduces genotoxicity. We previously reported that MTH1 is an efficient catalyst of O6-methyl-dGTP hydrolysis suggesting that MTH1 may also sanitize the nucleotide pool from other methylated nucleotides. We here show that MTH1 efficiently catalyzes the hydrolysis of N6-methyl-dATP to N6-methyl-dAMP and further report that N6-methylation of dATP drastically increases the MTH1 activity. We also observed MTH1 activity with N6-methyl-ATP, albeit at a lower level. We show that N6-methyl-dATP is incorporated into DNA in vivo, as indicated by increased N6-methyl-dA DNA levels in embryos developed from MTH1 knock-out zebrafish eggs microinjected with N6-methyl-dATP compared with noninjected embryos. N6-methyl-dATP activity is present in MTH1 homologues from distantly related vertebrates, suggesting evolutionary conservation and indicating that this activity is important. Of note, N6-methyl-dATP activity is unique to MTH1 among related NUDIX hydrolases. Moreover, we present the structure of N6-methyl-dAMP-bound human MTH1, revealing that the N6-methyl group is accommodated within a hydrophobic active-site subpocket explaining why N6-methyl-dATP is a good MTH1 substrate. N6-methylation of DNA and RNA has been reported to have epigenetic roles and to affect mRNA metabolism. We propose that MTH1 acts in concert with adenosine deaminase-like protein isoform 1 (ADAL1) to prevent incorporation of N6-methyl-(d)ATP into DNA and RNA. This would hinder potential dysregulation of epigenetic control and RNA metabolism via conversion of N6-methyl-(d)ATP to N6-methyl-(d)AMP, followed by ADAL1-catalyzed deamination producing (d)IMP that can enter the nucleotide salvage pathway.

Paper title : MutT homologue 1 (MTH1) catalyzes the hydrolysis of mutagenic O6-methyl-dGTP.

Doi : https://doi.org/10.1093/nar/gky896

Abstract : Nucleotides in the free pool are more susceptible to nonenzymatic methylation than those protected in the DNA double helix. Methylated nucleotides like O6-methyl-dGTP can be mutagenic and toxic if incorporated into DNA. Removal of methylated nucleotides from the nucleotide pool may therefore be important to maintain genome integrity. We show that MutT homologue 1 (MTH1) efficiently catalyzes the hydrolysis of O6-methyl-dGTP with a catalytic efficiency similar to that for 8-oxo-dGTP. O6-methyl-dGTP activity is exclusive to MTH1 among human NUDIX proteins and conserved through evolution but not found in bacterial MutT. We present a high resolution crystal structure of human and zebrafish MTH1 in complex with O6-methyl-dGMP. By microinjecting fertilized zebrafish eggs with O6-methyl-dGTP and inhibiting MTH1 we demonstrate that survival is dependent on active MTH1 in vivo. O6-methyl-dG levels are higher in DNA extracted from zebrafish embryos microinjected with O6-methyl-dGTP and inhibition of O6-methylguanine-DNA methyl transferase (MGMT) increases the toxicity of O6-methyl-dGTP demonstrating that O6-methyl-dGTP is incorporated into DNA. MTH1 deficiency sensitizes human cells to the alkylating agent Temozolomide, a sensitization that is more pronounced upon MGMT inhibition. These results expand the cellular MTH1 function and suggests MTH1 also is important for removal of methylated nucleotides from the nucleotide pool.

Paper title : MTH1 Substrate Recognition--An Example of Specific Promiscuity.

Doi : https://doi.org/10.1371/journal.pone.0151154

Abstract : MTH1 (NUDT1) is an oncologic target involved in the prevention of DNA damage. We investigate the way MTH1 recognises its substrates and present substrate-bound structures of MTH1 for 8-oxo-dGTP and 8-oxo-rATP as examples of novel strong and weak binding substrate motifs. Investigation of a small set of purine-like fragments using 2D NMR resulted in identification of a fragment with weak potency. The protein-ligand X-Ray structure of this fragment provides insight into the role of water molecules in substrate selectivity. Wider fragment screening by NMR resulted in three new protein structures exhibiting alternative binding configurations to the key Asp-Asp recognition element of the protein. These inhibitor binding modes demonstrate that MTH1 employs an intricate yet promiscuous mechanism of substrate anchoring through its Asp-Asp pharmacophore. The structures suggest that water-mediated interactions convey selectivity towards oxidized substrates over their non-oxidised counterparts, in particular by stabilization of a water molecule in a hydrophobic environment through hydrogen bonding. These findings may be useful in the design of inhibitors of MTH1.

Paper title : NF-kappaB inhibition increases chemosensitivity to trichostatin A-induced cell death of Ki-Ras-transformed human prostate epithelial cells.

Doi : https://doi.org/10.1093/carcin/bgl097

Abstract : Chemoresistance has been one of the major problems in anticancer therapy. In our effort to find a potential molecular target for overcoming the chemoresistance in prostate cancer, a promising anticancer drug trichostatin A (TSA) induced cell death was found to be compromised by enhanced NF-kappaB activation in 267B1/K-ras human prostate epithelial cancer cells. However, both the NF-kappaB activation and chemoresistance were reduced by pretreatment with proteasome inhibitor-I (ProI), accompanied by accumulations of both IkappaBalpha and p65/RelA (but not p50/NF-kappaB1) in the cytoplasm. Clonogenic cell survival and soft agar assays further confirmed the increased TSA chemosensitivity of 267B1/K-ras cells by ProI treatment. Moreover, dominant negative mutant of IKKbeta, IkappaBalpha and p65 enhanced the chemosensitization, too. Unexpectedly, using LY294002 and PD98059, phosphatidylinositol-3-kinase and mitogen-activated protein kinase were also implied in TSA chemoresistance through NF-kappaB activation, while these compounds had showed no effect on radiosensitization in the cells. On the other hand, together with TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) assay, activations of caspase-8 and caspase-3 by TSA and ProI were noticed, suggesting the involvement of apoptotic process in chemosensitization of 267B1/K-ras cells. Altogether, these results suggest that blocking the NF-kappaB activation pathway could be an efficient target for improving the TSA chemosensitization and applying to the development of anticancer therapeutics in Ki-Ras-overexpressing tumorigenic cells, including prostate cancer.

Paper title : The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).

Doi : https://doi.org/10.1101/gr.2596504

Abstract : The National Institutes of Health's Mammalian Gene Collection (MGC) project was designed to generate and sequence a publicly accessible cDNA resource containing a complete open reading frame (ORF) for every human and mouse gene. The project initially used a random strategy to select clones from a large number of cDNA libraries from diverse tissues. Candidate clones were chosen based on 5'-EST sequences, and then fully sequenced to high accuracy and analyzed by algorithms developed for this project. Currently, more than 11,000 human and 10,000 mouse genes are represented in MGC by at least one clone with a full ORF. The random selection approach is now reaching a saturation point, and a transition to protocols targeted at the missing transcripts is now required to complete the mouse and human collections. Comparison of the sequence of the MGC clones to reference genome sequences reveals that most cDNA clones are of very high sequence quality, although it is likely that some cDNAs may carry missense variants as a consequence of experimental artifact, such as PCR, cloning, or reverse transcriptase errors. Recently, a rat cDNA component was added to the project, and ongoing frog (Xenopus) and zebrafish (Danio) cDNA projects were expanded to take advantage of the high-throughput MGC pipeline.

Paper title : MTH1 inhibition eradicates cancer by preventing sanitation of the dNTP pool.

Doi : https://doi.org/10.1038/nature13181

Abstract : Cancers have dysfunctional redox regulation resulting in reactive oxygen species production, damaging both DNA and free dNTPs. The MTH1 protein sanitizes oxidized dNTP pools to prevent incorporation of damaged bases during DNA replication. Although MTH1 is non-essential in normal cells, we show that cancer cells require MTH1 activity to avoid incorporation of oxidized dNTPs, resulting in DNA damage and cell death. We validate MTH1 as an anticancer target in vivo and describe small molecules TH287 and TH588 as first-in-class nudix hydrolase family inhibitors that potently and selectively engage and inhibit the MTH1 protein in cells. Protein co-crystal structures demonstrate that the inhibitors bind in the active site of MTH1. The inhibitors cause incorporation of oxidized dNTPs in cancer cells, leading to DNA damage, cytotoxicity and therapeutic responses in patient-derived mouse xenografts. This study exemplifies the non-oncogene addiction concept for anticancer treatment and validates MTH1 as being cancer phenotypic lethal.

Paper title : An oxidized purine nucleoside triphosphatase, MTH1, suppresses cell death caused by oxidative stress.

Doi : https://doi.org/10.1074/jbc.M306201200

Abstract : MTH1 hydrolyzes oxidized purine nucleoside triphosphates such as 8-oxo-2'-deoxyguanosine 5'-triphosphate (8-oxo-dGTP) and 2-hydroxy-2'-deoxyadenosine 5'-triphosphate (2-OH-dATP) and thus protects cells from damage caused by their misincorporation into DNA. In the present study, we established MTH1-null mouse embryo fibroblasts that were highly susceptible to cell dysfunction and death caused by exposure to H2O2, with morphological features of pyknosis and electron-dense deposits accumulated in mitochondria. The cell death observed was independent of both poly(ADP-ribose) polymerase and caspases. A high performance liquid chromatography tandem mass spectrometry analysis and immunofluorescence microscopy revealed a continuous accumulation of 8-oxo-guanine both in nuclear and mitochondrial DNA after exposure to H2O2. All of the H2O2-induced alterations observed in MTH1-null mouse embryo fibroblasts were effectively suppressed by the expression of wild type human MTH1 (hMTH1), whereas they were only partially suppressed by the expression of mutant hMTH1 defective in either 8-oxo-dGTPase or 2-OH-dATPase activity. Human MTH1 thus protects cells from H2O2-induced cell dysfunction and death by hydrolyzing oxidized purine nucleotides including 8-oxo-dGTP and 2-OH-dATP, and these alterations may be partly attributed to a mitochondrial dysfunction.

Paper title : Structural and Kinetic Studies of the Human Nudix Hydrolase MTH1 Reveal the Mechanism for Its Broad Substrate Specificity.

Doi : https://doi.org/10.1074/jbc.M116.749713

Abstract : The human MutT homolog 1 (hMTH1, human NUDT1) hydrolyzes oxidatively damaged nucleoside triphosphates and is the main enzyme responsible for nucleotide sanitization. hMTH1 recently has received attention as an anticancer target because hMTH1 blockade leads to accumulation of oxidized nucleotides in the cell, resulting in mutations and death of cancer cells. Unlike Escherichia coli MutT, which shows high substrate specificity for 8-oxoguanine nucleotides, hMTH1 has broad substrate specificity for oxidized nucleotides, including 8-oxo-dGTP and 2-oxo-dATP. However, the reason for this broad substrate specificity remains unclear. Here, we determined crystal structures of hMTH1 in complex with 8-oxo-dGTP or 2-oxo-dATP at neutral pH. These structures based on high quality data showed that the base moieties of two substrates are located on the similar but not the same position in the substrate binding pocket and adopt a different hydrogen-bonding pattern, and both triphosphate moieties bind to the hMTH1 Nudix motif (i.e. the hydrolase motif) similarly and align for the hydrolysis reaction. We also performed kinetic assays on the substrate-binding Asp-120 mutants (D120N and D120A), and determined their crystal structures in complex with the substrates. Analyses of bond lengths with high-resolution X-ray data and the relationship between the structure and enzymatic activity revealed that hMTH1 recognizes the different oxidized nucleotides via an exchange of the protonation state at two neighboring aspartate residues (Asp-119 and Asp-120) in its substrate binding pocket. To our knowledge, this mechanism of broad substrate recognition by enzymes has not been reported previously and may have relevance for anticancer drug development strategies targeting hMTH1.

Paper title : Crystal structure of human MTH1 and the 8-oxo-dGMP product complex.

Doi : https://doi.org/10.1016/j.febslet.2011.07.017

Abstract : MTH1 hydrolyzes oxidized nucleotide triphosphates, thereby preventing them from being incorporated into DNA. We here present the structures of human MTH1 (1.9Å) and its complex with the product 8-oxo-dGMP (1.8Å). Unexpectedly MTH1 binds the nucleotide in the anti conformation with no direct interaction between the 8-oxo group and the protein. We suggest that the specificity depends on the stabilization of an enol tautomer of the 8-oxo form of dGTP. The binding of the product induces no major structural changes. The structures reveal the mode of nucleotide binding in MTH1 and provide the structural basis for inhibitor design.

Paper title : The oxidized forms of dATP are substrates for the human MutT homologue, the hMTH1 protein.

Doi : https://doi.org/10.1074/jbc.274.26.18201

Abstract : The possibility that Escherichia coli MutT and human MTH1 (hMTH1) hydrolyze oxidized DNA precursors other than 8-hydroxy-dGTP (8-OH-dGTP) was investigated. We report here that hMTH1 hydrolyzed 2-hydroxy-dATP (2-OH-dATP) and 8-hydroxy-dATP (8-OH-dATP), oxidized forms of dATP, but not (R)-8,5'-cyclo-dATP, 5-hydroxy-dCTP, and 5-formyl-dUTP. The kinetic parameters indicated that 2-OH-dATP was hydrolyzed more efficiently and with higher affinity than 8-OH-dGTP. 8-OH-dATP was hydrolyzed as efficiently as 8-OH-dGTP. The preferential hydrolysis of 2-OH-dATP over 8-OH-dGTP was observed at all of the pH values tested (pH 7.2 to pH 8.8). In particular, a 5-fold difference in the hydrolysis efficiencies for 2-OH-dATP over 8-OH-dGTP was found at pH 7.2. However, E. coli MutT had no hydrolysis activity for either 2-OH-dATP or 8-OH-dATP. Thus, E. coli MutT is an imperfect counterpart for hMTH1. Furthermore, we found that 2-hydroxy-dADP and 8-hydroxy-dGDP competitively inhibited both the 2-OH-dATP hydrolase and 8-OH-dGTP hydrolase activities of hMTH1. The inhibitory effects of 2-hydroxy-dADP were 3-fold stronger than those of 8-hydroxy-dGDP. These results suggest that the three damaged nucleotides share the same recognition site of hMTH1 and that it is a more important sanitization enzyme than expected thus far.

Paper title : A molecular basis for the selective recognition of 2-hydroxy-dATP and 8-oxo-dGTP by human MTH1.

Doi : https://doi.org/10.1074/jbc.M110566200

Abstract : MTH1 hydrolyzes oxidized purine nucleoside triphosphates such as 8-oxo-dGTP, 8-oxo-dATP, 2-hydroxy-dATP, and 2-hydroxy rATP to monophosphates, and thus avoids errors caused by their misincorporation during DNA replication or transcription, which may result in carcinogenesis or neurodegeneration. This substrate specificity for oxidized purine nucleoside triphosphates was investigated by mutation analyses based on the sequence comparison with the Escherichia coli homolog, MutT, which hydrolyzes only 8-oxo-dGTP and 8-oxo-rGTP but not oxidized forms of dATP or ATP. Neither a replacement of the phosphohydrolase module of MTH1 with that of MutT nor deletions of the C-terminal region of MTH1, which is unique for MTH1, altered the substrate specificity of MTH1. In contrast, the substitution of residues at position Trp-117 and Asp-119 of MTH1, which showed apparent chemical shift perturbations with 8-oxo-dGDP in NMR analyses but are not conserved in MutT, affected the substrate specificity. Trp-117 is essential for MTH1 to recognize both 8-oxo-dGTP and 2-hydroxy-dATP, whereas Asp-119 is only essential for recognizing 2-hydroxy-dATP, thus suggesting that origins of the substrate-binding pockets for MTH1 and MutT are different.