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Qian J, Ma Y, Tahaney WM, Moyer CL, Lanier A, Hill J, Coleman D, Koupaei N, Hilsenbeck SG, Savage MI, Page BDG, Mazumdar A, Brown PH. The novel phosphatase NUDT5 is a critical regulator of triple-negative breast cancer growth. Breast Cancer Res 2024; 26:23. [PMID: 38317231 PMCID: PMC10845800 DOI: 10.1186/s13058-024-01778-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 01/22/2024] [Indexed: 02/07/2024] Open
Abstract
BACKGROUND The most aggressive form of breast cancer is triple-negative breast cancer (TNBC), which lacks expression of the estrogen receptor (ER) and progesterone receptor (PR), and does not have overexpression of the human epidermal growth factor receptor 2 (HER2). Treatment options for women with TNBC tumors are limited, unlike those with ER-positive tumors that can be treated with hormone therapy, or those with HER2-positive tumors that can be treated with anti-HER2 therapy. Therefore, we have sought to identify novel targeted therapies for TNBC. In this study, we investigated the potential of a novel phosphatase, NUDT5, as a potential therapeutic target for TNBC. METHODS The mRNA expression levels of NUDT5 in breast cancers were investigated using TCGA and METABRIC (Curtis) datasets. NUDT5 ablation was achieved through siRNA targeting and NUDT5 inhibition with the small molecule inhibitor TH5427. Xenograft TNBC animal models were employed to assess the effect of NUDT5 inhibition on in vivo tumor growth. Proliferation, death, and DNA replication assays were conducted to investigate the cellular biological effects of NUDT5 loss or inhibition. The accumulation of 8-oxo-guanine (8-oxoG) and the induction of γH2AX after NUDT5 loss was determined by immunofluorescence staining. The impact of NUDT5 loss on replication fork was assessed by measuring DNA fiber length. RESULTS In this study, we demonstrated the significant role of an overexpressed phosphatase, NUDT5, in regulating oxidative DNA damage in TNBCs. Our findings indicate that loss of NUDT5 results in suppressed growth of TNBC both in vitro and in vivo. This growth inhibition is not attributed to cell death, but rather to the suppression of proliferation. The loss or inhibition of NUDT5 led to an increase in the oxidative DNA lesion 8-oxoG, and triggered the DNA damage response in the nucleus. The interference with DNA replication ultimately inhibited proliferation. CONCLUSIONS NUDT5 plays a crucial role in preventing oxidative DNA damage in TNBC cells. The loss or inhibition of NUDT5 significantly suppresses the growth of TNBCs. These biological and mechanistic studies provide the groundwork for future research and the potential development of NUDT5 inhibitors as a promising therapeutic approach for TNBC patients.
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Affiliation(s)
- Jing Qian
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- The University of Texas MD Anderson Cancer Center UTHealth Houston Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Yanxia Ma
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Department of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - William M Tahaney
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
- Monte Rosa Therapeutics, Boston, USA
| | - Cassandra L Moyer
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Amanda Lanier
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Jamal Hill
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Darian Coleman
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Negar Koupaei
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Department of Breast Surgical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Susan G Hilsenbeck
- Lester and Sue Smith Breast Center and Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, TX, USA
| | - Michelle I Savage
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Brent D G Page
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada
| | - Abhijit Mazumdar
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Powel H Brown
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA.
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Wang M, Feng Y, Cao Z, Yu N, Wang J, Wang X, Kang D, Su M, Hu J, Du H. Multiple generation exposure to ZnO nanoparticles induces loss of genomic integrity in Caenorhabditis elegans. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2023; 249:114383. [PMID: 36508841 DOI: 10.1016/j.ecoenv.2022.114383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 11/27/2022] [Accepted: 12/01/2022] [Indexed: 06/17/2023]
Abstract
Zinc oxide nanoparticles (ZnO NPs) are commonly used in industrial and household applications, prompting the assessment of their associated health risks. Previous studies indicated that ZnO NPs can induce somatic cell mutations, while the aging process appears to increase the mutagenicity of ZnO NPs. However, little is known about the influence of ZnO NPs on genome stability of germ cells, and non-exposed progeny. Here we show that 20 nm ZnO NPs exposure disrupts germ cell development, and elevates the overall mutation frequency of germ cells in Caenorhabditis elegans (C. elegans). We observed that pristine ZnO NPs elicit germ cell apoptosis to a greater extent than the 60-day aged ZnO NPs. By treating parental worms with ZnO NPs for seven successive generations, whole-genome sequencing data revealed that, although the frequency of point mutations is kept unchanged, large deletions are significantly increased in F8 worms. Furthermore, we found that the mutagenicity of ZnO NPs might be partially attributed to the release of Zn2+ ions. Together, our results demonstrate the genotoxic effects of ZnO NPs on germ cells, and the possible underlying mechanism. These findings suggest that germ cell mutagenicity is worthy of consideration for the health risk assessment of engineered NPs.
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Affiliation(s)
- Meimei Wang
- Department of Pathophysiology, School of Basic Medical Science, Anhui Medical University, No. 81, Mei-Shan Road, Hefei 230032, Anhui, PR China.
| | - Yu Feng
- High Magnetic Field Laboratory, Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, PR China
| | - Zhenxiao Cao
- High Magnetic Field Laboratory, Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, PR China; School of Environmental Science and Optoelectronic Technology, University of Science and Technology of China, Hefei 230026, PR China
| | - Na Yu
- Department of Pathophysiology, School of Basic Medical Science, Anhui Medical University, No. 81, Mei-Shan Road, Hefei 230032, Anhui, PR China
| | - Juan Wang
- Department of Public Health Inspection and Quarantine, School of Public Health, Anhui Medical University, Hefei 230032, Anhui, PR China
| | - Xiaowei Wang
- Department of Pathophysiology, School of Basic Medical Science, Anhui Medical University, No. 81, Mei-Shan Road, Hefei 230032, Anhui, PR China
| | - Dixiang Kang
- Department of Pathophysiology, School of Basic Medical Science, Anhui Medical University, No. 81, Mei-Shan Road, Hefei 230032, Anhui, PR China
| | - Mingqin Su
- Department of Pathophysiology, School of Basic Medical Science, Anhui Medical University, No. 81, Mei-Shan Road, Hefei 230032, Anhui, PR China
| | - Jian Hu
- Department of Pathophysiology, School of Basic Medical Science, Anhui Medical University, No. 81, Mei-Shan Road, Hefei 230032, Anhui, PR China
| | - Hua Du
- High Magnetic Field Laboratory, Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, Anhui, PR China.
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Leuthner T, Benzing L, Kohrn B, Bergemann C, Hipp M, Hershberger K, Mello D, Sokolskyi T, Stevenson K, Merutka I, Seay S, Gregory S, Kennedy S, Meyer J. Resistance of mitochondrial DNA to cadmium and Aflatoxin B1 damage-induced germline mutation accumulation in C. elegans. Nucleic Acids Res 2022; 50:8626-8642. [PMID: 35947695 PMCID: PMC9410910 DOI: 10.1093/nar/gkac666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 07/11/2022] [Accepted: 07/22/2022] [Indexed: 01/12/2023] Open
Abstract
Mitochondrial DNA (mtDNA) is prone to mutation in aging and over evolutionary time, yet the processes that regulate the accumulation of de novo mtDNA mutations and modulate mtDNA heteroplasmy are not fully elucidated. Mitochondria lack certain DNA repair processes, which could contribute to polymerase error-induced mutations and increase susceptibility to chemical-induced mtDNA mutagenesis. We conducted error-corrected, ultra-sensitive Duplex Sequencing to investigate the effects of two known nuclear genome mutagens, cadmium and Aflatoxin B1, on germline mtDNA mutagenesis in Caenorhabditis elegans. Detection of thousands of mtDNA mutations revealed pervasive heteroplasmy in C. elegans and that mtDNA mutagenesis is dominated by C:G → A:T mutations generally attributed to oxidative damage. However, there was no effect of either exposure on mtDNA mutation frequency, spectrum, or trinucleotide context signature despite a significant increase in nuclear mutation rate after aflatoxin B1 exposure. Mitophagy-deficient mutants pink-1 and dct-1 accumulated significantly higher levels of mtDNA damage compared to wild-type C. elegans after exposures. However, there were only small differences in mtDNA mutation frequency, spectrum, or trinucleotide context signature compared to wild-type after 3050 generations, across all treatments. These findings suggest mitochondria harbor additional previously uncharacterized mechanisms that regulate mtDNA mutational processes across generations.
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Affiliation(s)
- Tess C Leuthner
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Laura Benzing
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Brendan F Kohrn
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA 98195, USA
| | | | - Michael J Hipp
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA 98195, USA
| | | | - Danielle F Mello
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Tymofii Sokolskyi
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Kevin Stevenson
- Duke Molecular Physiology Institute, Duke University, Durham, NC 27701, USA
| | - Ilaria R Merutka
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Sarah A Seay
- Nicholas School of the Environment, Duke University, Durham, NC 27708, USA
| | - Simon G Gregory
- Duke Molecular Physiology Institute, Duke University, Durham, NC 27701, USA,Department of Neurology, Duke University, Durham, NC 27708, USA
| | - Scott R Kennedy
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA 98195, USA
| | - Joel N Meyer
- To whom correspondence should be addressed. Tel: +1 919 613 8109;
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Gartner A, Engebrecht J. DNA repair, recombination, and damage signaling. Genetics 2021; 220:6522877. [PMID: 35137093 PMCID: PMC9097270 DOI: 10.1093/genetics/iyab178] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 10/10/2021] [Indexed: 01/09/2023] Open
Abstract
DNA must be accurately copied and propagated from one cell division to the next, and from one generation to the next. To ensure the faithful transmission of the genome, a plethora of distinct as well as overlapping DNA repair and recombination pathways have evolved. These pathways repair a large variety of lesions, including alterations to single nucleotides and DNA single and double-strand breaks, that are generated as a consequence of normal cellular function or by external DNA damaging agents. In addition to the proteins that mediate DNA repair, checkpoint pathways have also evolved to monitor the genome and coordinate the action of various repair pathways. Checkpoints facilitate repair by mediating a transient cell cycle arrest, or through initiation of cell suicide if DNA damage has overwhelmed repair capacity. In this chapter, we describe the attributes of Caenorhabditis elegans that facilitate analyses of DNA repair, recombination, and checkpoint signaling in the context of a whole animal. We review the current knowledge of C. elegans DNA repair, recombination, and DNA damage response pathways, and their role during development, growth, and in the germ line. We also discuss how the analysis of mutational signatures in C. elegans is helping to inform cancer mutational signatures in humans.
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Affiliation(s)
- Anton Gartner
- Department for Biological Sciences, IBS Center for Genomic Integrity, Ulsan National Institute of Science and Technology, Ulsan 689-798, Republic of Korea,Corresponding author: (A.G.); (J.E.)
| | - JoAnne Engebrecht
- Department of Molecular and Cellular Biology, University of California Davis, Davis, CA 95616, USA,Corresponding author: (A.G.); (J.E.)
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AP endonuclease EXO-3 deficiency causes developmental delay and abnormal vulval organogenesis, Pvl, through DNA glycosylase-initiated checkpoint activation in Caenorhabditis elegans. Sci Rep 2018; 8:16736. [PMID: 30425296 PMCID: PMC6233223 DOI: 10.1038/s41598-018-35063-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 10/25/2018] [Indexed: 12/27/2022] Open
Abstract
AP endonuclease deficiency causes cell death and embryonic lethality in mammals. However, the physiological roles of AP endonucleases in multicellular organisms remain unclear, especially after embryogenesis. Here, we report novel physiological roles of the AP endonuclease EXO-3 from larval to adult stages in Caenorhabditis elegans, and elucidated the mechanism of the observed phenotypes due to EXO-3 deficiency. The exo-3 mutants exhibited developmental delay, whereas the apn-1 mutants did not. The delay depended on the DNA glycosylase NTH-1 and checkpoint kinase CHK-2. The exo-3 mutants had further developmental delay when treated with AP site-generating agents such as methyl methane sulfonate and sodium bisulfite. The further delay due to sodium bisulfite was dependent on the DNA glycosylase UNG-1. The exo-3 mutants also demonstrated an increase in dut-1 (RNAi)-induced abnormal vulval organogenesis protruding vulva (Pvl), whereas the apn-1 mutants did not. The increase in Pvl was dependent on UNG-1 and CHK-2. Methyl viologen, ndx-1 (RNAi) and ndx-2 (RNAi) enhanced the incidence of Pvl among exo-3 mutants only when combined with dut-1 (RNAi). This further increase in Pvl incidence was independent of NTH-1. These results indicate that EXO-3 prevents developmental delay and Pvl in C. elegans, which are induced via DNA glycosylase-initiated checkpoint activation.
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Sanada Y, Zhang-Akiyama QM. An increase of oxidised nucleotides activates DNA damage checkpoint pathway that regulates post-embryonic development in Caenorhabditis elegans. Mutagenesis 2014; 29:107-14. [PMID: 24435662 DOI: 10.1093/mutage/get067] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
8-Oxo-dGTP, an oxidised form of dGTP generated in the nucleotide pool, can be incorporated opposite adenine or cytosine in template DNA, which can in turn induce mutations. In this study, we identified a novel MutT homolog (NDX-2) of Caenorhabditis elegans that hydrolyzes 8-oxo-dGDP to 8-oxo-dGMP. In addition, we found that NDX-1, NDX-2 and NDX-4 proteins have 8-oxo-GTPase or 8-oxo-GDPase activity. The sensitivity of ndx-2 knockdown C. elegans worms to methyl viologen and menadione bisulphite was increased compared with that of control worms. This sensitivity was rescued by depletion of chk-2 and clk-2, suggesting that growth of the worms is regulated by the checkpoint pathway in response to the accumulation of oxidised nucleotides. Moreover, we found that the sensitivity to menadione bisulphite of ndx-1 and ndx-2-double knockdown worms was enhanced by elimination of XPA-1, a factor involved in nucleotide excision repair. The rescue effect by depletion of chk-2 and clk-2 was limited in the xpa-1 mutant, suggesting that the chk-2 and clk-2 checkpoint pathway is partially linked to the function of XPA-1.
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Affiliation(s)
- Yu Sanada
- Department of Zoology, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
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McLennan AG. Substrate ambiguity among the nudix hydrolases: biologically significant, evolutionary remnant, or both? Cell Mol Life Sci 2013; 70:373-85. [PMID: 23184251 PMCID: PMC11113851 DOI: 10.1007/s00018-012-1210-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 11/01/2012] [Accepted: 11/05/2012] [Indexed: 12/20/2022]
Abstract
Many members of the nudix hydrolase family exhibit considerable substrate multispecificity and ambiguity, which raises significant issues when assessing their functions in vivo and gives rise to errors in database annotation. Several display low antimutator activity when expressed in bacterial tester strains as well as some degree of activity in vitro towards mutagenic, oxidized nucleotides such as 8-oxo-dGTP. However, many of these show greater activity towards other nucleotides such as ADP-ribose or diadenosine tetraphosphate (Ap(4)A). The antimutator activities have tended to gain prominence in the literature, whereas they may in fact represent the residual activity of an ancestral antimutator enzyme that has become secondary to the more recently evolved major activity after gene duplication. Whether any meaningful antimutagenic function has also been retained in vivo requires very careful assessment. Then again, other examples of substrate ambiguity may indicate as yet unexplored regulatory systems. For example, bacterial Ap(4)A hydrolases also efficiently remove pyrophosphate from the 5' termini of mRNAs, suggesting a potential role for Ap(4)A in the control of bacterial mRNA turnover, while the ability of some eukaryotic mRNA decapping enzymes to degrade IDP and dIDP or diphosphoinositol polyphosphates (DIPs) may also be indicative of new regulatory networks in RNA metabolism. DIP phosphohydrolases also degrade diadenosine polyphosphates and inorganic polyphosphates, suggesting further avenues for investigation. This article uses these and other examples to highlight the need for a greater awareness of the possible significance of substrate ambiguity among the nudix hydrolases as well as the need to exert caution when interpreting incomplete analyses.
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Affiliation(s)
- Alexander G McLennan
- Institute of Integrative Biology, University of Liverpool, Biosciences Building, Crown St., Liverpool, L69 7ZB, UK.
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Functional characterization of the Caenorhabditis elegans DNA repair enzyme APN-1. DNA Repair (Amst) 2012; 11:811-22. [PMID: 22819077 DOI: 10.1016/j.dnarep.2012.06.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Revised: 05/17/2012] [Accepted: 06/29/2012] [Indexed: 11/23/2022]
Abstract
Caenorhabditis elegans possesses two distinct DNA repair enzymes EXO-3 and APN-1 that have been identified by cross-specie complementation analysis of the Saccharomyces cerevisiae apn1Δapn2Δtpp1Δ triple mutant deficient in the ability to repair apurinic/apyrimidinc (AP) sites and DNA strand breaks with blocked 3'-ends. While purified EXO-3 directly incises AP sites and removes 3'-blocking groups, such characterization has not been previously reported for APN-1. We recently documented that C. elegans knockdown for apn-1 is unable to maintain integrity of the genome. Despite the presence of EXO-3, the apn-1 knockdown animals are also defective in the division of the P1 blastomere, an observation consistent with the accumulation of unrepaired DNA lesions suggesting a unique role for APN-1 DNA repair functions. Herein, we show that C. elegans APN-1 is stably expressed as GST-fusion protein in S. cerevisiae only when it carries a nuclear localization signal, and with this requirement rescued the DNA repair defects of the S. cerevisiae apn1Δapn2Δtpp1Δ triple mutant. We purified the APN-1 from the yeast expression system and established that it displays AP endonuclease and 3'-diesterase activities. In addition, we showed that APN-1 also possesses a 3'- to 5'-exonuclease and the nucleotide incision repair activity. This latter activity is capable of directly incising DNA at the 5'-side of various oxidatively damaged bases, as previously observed for Escherichia coli endonuclease IV and S. cerevisiae Apn1, underscoring the importance of this family of enzymes in removing these types of lesions. Glycine substitution of the conserved amino acid residue Glu261 of APN-1, corresponding to Glu145 involved in coordinating Zn(2+) ions in the active site pocket of E. coli endonuclease IV, resulted in an inactive variant that lose the ability to rescue the DNA repair defects of S. cerevisiae apn1Δapn2Δtpp1Δ mutant. Interestingly, the Glu261Gly variant did not sustain purification and yielded a truncated polypeptide. These data suggest that the Glu261 residue of APN-1 may have a broader role in maintaining the structure of the protein.
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Takagi Y, Setoyama D, Ito R, Kamiya H, Yamagata Y, Sekiguchi M. Human MTH3 (NUDT18) protein hydrolyzes oxidized forms of guanosine and deoxyguanosine diphosphates: comparison with MTH1 and MTH2. J Biol Chem 2012; 287:21541-9. [PMID: 22556419 PMCID: PMC3375575 DOI: 10.1074/jbc.m112.363010] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 04/25/2012] [Indexed: 01/25/2023] Open
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.
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Affiliation(s)
| | | | - Riyoko Ito
- From the Fukuoka Dental College, Fukuoka 814-0193
| | - Hiroyuki Kamiya
- the Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, and
| | - Yuriko Yamagata
- the Graduate School of Pharmaceutical Science, Kumamoto University, Kumamoto 862-0973, Japan
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