1
|
Gutierrez R, Chan AY, Tsuen Lai SW, Itoh S, Lee DH, Sun K, Battad A, Chen S, O'Connor TR, Shuck SC. Lack of mismatch repair enhances resistance to methylating agents for cells deficient in oxidative demethylation. J Biol Chem 2024:107492. [PMID: 38925328 DOI: 10.1016/j.jbc.2024.107492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 05/21/2024] [Accepted: 05/31/2024] [Indexed: 06/28/2024] Open
Abstract
The human AlkB homologs, ALKBH2 and ALKBH3, respond to methylation damage to maintain genomic integrity and cellular viability. Both ALKBH2 and ALKBH3 are direct reversal repair (DRR) enzymes that remove 1meA and 3meC lesions commonly generated by alkylating chemotherapeutic agents. Thus, the existence of deficiencies in ALKBH proteins can be exploited in synergy with chemotherapy. In this study, we investigated possible interactions between ALKBH2 and ALKBH3 with other proteins that could alter damage response and discovered an interaction with the mismatch repair (MMR) system. To test whether the lack of active MMR impacts ALKBH2 and/or ALKBH3 response to methylating agents, we generated cells deficient in ALKBH2, ALKBH3, or both in addition to Mlh homolog 1 (MLH1), another MMR protein. We found that MLH1koALKBH3ko cells showed enhanced resistance towards SN1- and SN2-type methylating agents, whereas MLH1koALKBH2ko cells were only resistant to SN1-type methylating agents. Concomitant loss of ALKBH2 and ALKBH3 (ALKBH2ko3ko) rendered cells sensitive to SN1- and SN2-agents, but the additional loss of MLH1 enhanced resistance to both types of damage. We also showed that ALKBH2ko3ko cells have an ATR-dependent arrest at the G2/M checkpoint, increased apoptotic signalling, and replication fork stress in response to methylation. However, these responses were not observed with the loss of functional MLH1 in MLH1koALKBH2ko3ko cells. Finally, in MLH1koALKBH2ko3ko cells, we observed elevated mutant frequency in untreated and temozolomide treated cells. These results suggest that obtaining a more accurate prognosis of chemotherapeutic outcome requires information on the functionality of ALKBH2, ALKBH3, and MLH1.
Collapse
Affiliation(s)
- Roberto Gutierrez
- Department of Cancer Biology, Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute at the City of Hope, Duarte California, 91010 United States of America
| | - Annie Yin Chan
- Department of Cancer Biology, Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute at the City of Hope, Duarte California, 91010 United States of America
| | - Seigmund Wai Tsuen Lai
- Department of Diabetes and Cancer Metabolism, Beckman Research Institute at the City of Hope, Duarte California, 91010 United States of America
| | - Shunsuke Itoh
- Department of Cancer Biology, Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute at the City of Hope, Duarte California, 91010 United States of America
| | - Dong-Hyun Lee
- Department of Biological Sciences, College of Natural Sciences, Chonnam National University, Gwangju 61186 South Korea
| | - Kelani Sun
- Department of Diabetes and Cancer Metabolism, Beckman Research Institute at the City of Hope, Duarte California, 91010 United States of America
| | - Alana Battad
- Department of Diabetes and Cancer Metabolism, Beckman Research Institute at the City of Hope, Duarte California, 91010 United States of America
| | - Shiuan Chen
- Department of Cancer Biology, Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute at the City of Hope, Duarte California, 91010 United States of America
| | - Timothy R O'Connor
- Department of Cancer Biology, Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute at the City of Hope, Duarte California, 91010 United States of America.
| | - Sarah C Shuck
- Department of Diabetes and Cancer Metabolism, Beckman Research Institute at the City of Hope, Duarte California, 91010 United States of America.
| |
Collapse
|
2
|
Tomar MS, Kumar A, Srivastava C, Shrivastava A. Elucidating the mechanisms of Temozolomide resistance in gliomas and the strategies to overcome the resistance. Biochim Biophys Acta Rev Cancer 2021; 1876:188616. [PMID: 34419533 DOI: 10.1016/j.bbcan.2021.188616] [Citation(s) in RCA: 102] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Revised: 07/25/2021] [Accepted: 08/15/2021] [Indexed: 02/06/2023]
Abstract
Temozolomide (TMZ) is a first-choice alkylating agent inducted as a gold standard therapy for glioblastoma multiforme (GBM) and astrocytoma. A majority of patients do not respond to TMZ during the course of their treatment. Activation of DNA repair pathways is the principal mechanism for this phenomenon that detaches TMZ-induced O-6-methylguanine adducts and restores genomic integrity. Current understanding in the domain of oncology adds several other novel mechanisms of resistance such as the involvement of miRNAs, drug efflux transporters, gap junction's activity, the advent of glioma stem cells as well as upregulation of cell survival autophagy. This review describes a multifaceted account of different mechanisms responsible for the intrinsic and acquired TMZ-resistance. Here, we summarize different strategies that intensify the TMZ effect such as MGMT inhibition, development of novel imidazotetrazine analog, and combination therapy; with an aim to incorporate a successful treatment and increased overall survival in GBM patients.
Collapse
Affiliation(s)
- Manendra Singh Tomar
- Center for Advance Research, Faculty of Medicine, King George's Medical University, Lucknow 226003, Uttar Pradesh, India
| | - Ashok Kumar
- Department of Biochemistry, All India Institute of Medical Sciences (AIIMS) Bhopal, Saket Nagar, Bhopal 462020, Madhya Pradesh, India
| | - Chhitij Srivastava
- Department of Neurosurgery, King George's Medical University, Lucknow 226003, Uttar Pradesh, India
| | - Ashutosh Shrivastava
- Center for Advance Research, Faculty of Medicine, King George's Medical University, Lucknow 226003, Uttar Pradesh, India.
| |
Collapse
|
3
|
Goersch MCDS, Schäfer L, Tonial M, de Oliveira VR, Ferraz ADBF, Fachini J, da Silva JB, Niekraszewicz LAB, Rodrigues CE, Pasquali G, Dias JF, Kist TBL, Picada JN. Nutritional composition of Eragrostis teff and its association with the observed antimutagenic effects. RSC Adv 2019; 9:3764-3776. [PMID: 35518081 PMCID: PMC9060251 DOI: 10.1039/c8ra09733j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 01/09/2019] [Indexed: 12/28/2022] Open
Abstract
Eragrostis teff is an Ethiopian native grass plant (Poaceae or Gramineae family) whose importance as a crop grain has increased in recent years. The aim of this study is to analyze the nutritional composition of its seeds and the mutagenic/antimutagenic activity of the hydroalcoholic extract of the seed flour. Chemical elements (colloquially known as minerals) were determined using Particle-Induced X-ray Emission (PIXE) and Flame Atomic Absorption Spectroscopy (FAAS), while the content of amino acids (aminogram) and fatty acids (profile of fatty acids) were quantified by HPLC. Mutagenic activities were tested using Salmonella/microsome assay. Mutagens doxorubicin, 4-nitroquinolin N-oxide, methylmethanosulphonate, and aflatoxin B-1 were used in Salmonella typhimurium TA98 and TA100 strains to assess antimutagenic activities. The major elements observed were K, P, S, Mg, and Ca. Almost all essential amino acids were observed and the predominance of unsaturated fatty acids in the total oil content of 2.72% (w/w) is also noted, including the two essential fatty acids alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid). Hydroalcoholic extract of E. teff seed flour showed antimutagenic activity, protecting against frameshift and base pair substitution mutations. These findings provide valuable information for further development of healthier foods that can be produced with increasing yields and minimal environmental impact. Eragrostis teff is an Ethiopian native grass plant (Poaceae or Gramineae family) whose importance as a crop grain has increased in recent years.![]()
Collapse
Affiliation(s)
- Maria Clara da Silva Goersch
- Graduating Program in Cell and Molecular Biology Applied to Health, Laboratory of Toxicological Genetics, Lutheran University of Brazil (ULBRA) Farroupilha Avenue 8001 92425-900 Canoas RS Brazil +55 51 34771313 +55 51 34779158
| | - Laura Schäfer
- Laboratory of Methods, Department of Biophysics, Institute of Biosciences, Federal University of Rio Grande do Sul Bento Goncalves Avenue 9500 Porto Alegre RS Brazil
| | - Marina Tonial
- Laboratory of Methods, Department of Biophysics, Institute of Biosciences, Federal University of Rio Grande do Sul Bento Goncalves Avenue 9500 Porto Alegre RS Brazil
| | - Viviani Ruffo de Oliveira
- Department of Nutrition, Medical School, Federal University of Rio Grande do Sul Ramiro Barcelos Street 2400 Porto Alegre RS Brazil
| | | | - Jean Fachini
- Graduating Program in Cell and Molecular Biology Applied to Health, Laboratory of Toxicological Genetics, Lutheran University of Brazil (ULBRA) Farroupilha Avenue 8001 92425-900 Canoas RS Brazil +55 51 34771313 +55 51 34779158
| | - Juliana Bondan da Silva
- Graduating Program in Cell and Molecular Biology Applied to Health, Laboratory of Toxicological Genetics, Lutheran University of Brazil (ULBRA) Farroupilha Avenue 8001 92425-900 Canoas RS Brazil +55 51 34771313 +55 51 34779158
| | - Liana Appel Boufleur Niekraszewicz
- Ion Implantation Laboratory (LII), Institute of Physics, Federal University of Rio Grande do Sul Bento Goncalves Avenue 9500 Porto Alegre RS Brazil
| | - Carlos Eduardo Rodrigues
- Laboratory of Methods, Department of Biophysics, Institute of Biosciences, Federal University of Rio Grande do Sul Bento Goncalves Avenue 9500 Porto Alegre RS Brazil.,Graduating Program in Cell and Molecular Biology, Center for Biotechnology, Federal University of Rio Grande do Sul (UFRGS) Porto Alegre RS Brazil
| | - Giancarlo Pasquali
- Graduating Program in Cell and Molecular Biology, Center for Biotechnology, Federal University of Rio Grande do Sul (UFRGS) Porto Alegre RS Brazil
| | - Johnny Ferraz Dias
- Ion Implantation Laboratory (LII), Institute of Physics, Federal University of Rio Grande do Sul Bento Goncalves Avenue 9500 Porto Alegre RS Brazil
| | - Tarso B Ledur Kist
- Laboratory of Methods, Department of Biophysics, Institute of Biosciences, Federal University of Rio Grande do Sul Bento Goncalves Avenue 9500 Porto Alegre RS Brazil
| | - Jaqueline Nascimento Picada
- Graduating Program in Cell and Molecular Biology Applied to Health, Laboratory of Toxicological Genetics, Lutheran University of Brazil (ULBRA) Farroupilha Avenue 8001 92425-900 Canoas RS Brazil +55 51 34771313 +55 51 34779158
| |
Collapse
|
4
|
McKeague M, Otto C, Räz MH, Angelov T, Sturla SJ. The Base Pairing Partner Modulates Alkylguanine Alkyltransferase. ACS Chem Biol 2018; 13:2534-2541. [PMID: 30040894 DOI: 10.1021/acschembio.8b00446] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
O6-Alkylguanine DNA adducts are repaired by the suicide enzyme alkylguanine alkyltransferase (AGT). AGT facilitates repair by binding DNA in the minor groove, flipping out the damaged base, and transferring the O6-alkyl group to a cysteine residue in the enzyme's active site. Despite there being significant knowledge concerning the mechanism of AGT repair, there is limited insight regarding how altered interactions of the adduct with its complementary base in the DNA duplex influence its recognition and repair. In this study, the relationship of base pairing interactions and repair by human AGT (hAGT) was tested in the frequently mutated codon 12 of the KRAS gene with complementary sequences containing each canonical DNA base. The rate of O6-MeG repair decreased 2-fold when O6-MeG was paired with G, whereas all other canonical bases had no impact on the repair rate. We used a combination of biochemical studies, molecular modeling, and artificial nucleobases to elucidate the mechanism accounting for the 2-fold decrease. Our results suggest that the reduced rate of repair is due to O6-MeG adopting a syn conformation about the glycosidic bond precluding the formation of a repair-active complex. These data provide a novel chemical basis for how direct reversion repair may be impeded through modification of the base pair partner and support the use of artificial nucleobases as tools to probe the biochemistry of damage repair processes.
Collapse
Affiliation(s)
- Maureen McKeague
- Department of Health Sciences and Technology, ETH Zürich, Schmelzbergstrasse 9, 8092 Zürich, Switzerland
| | - Claudia Otto
- Department of Health Sciences and Technology, ETH Zürich, Schmelzbergstrasse 9, 8092 Zürich, Switzerland
| | - Michael H. Räz
- Department of Health Sciences and Technology, ETH Zürich, Schmelzbergstrasse 9, 8092 Zürich, Switzerland
| | - Todor Angelov
- Department of Health Sciences and Technology, ETH Zürich, Schmelzbergstrasse 9, 8092 Zürich, Switzerland
| | - Shana J. Sturla
- Department of Health Sciences and Technology, ETH Zürich, Schmelzbergstrasse 9, 8092 Zürich, Switzerland
| |
Collapse
|
5
|
Göder A, Nagel G, Kraus A, Dörsam B, Seiwert N, Kaina B, Fahrer J. Lipoic acid inhibits the DNA repair protein O 6-methylguanine-DNA methyltransferase (MGMT) and triggers its depletion in colorectal cancer cells with concomitant autophagy induction. Carcinogenesis 2015; 36:817-31. [PMID: 25998848 DOI: 10.1093/carcin/bgv070] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 05/10/2015] [Indexed: 11/13/2022] Open
Abstract
Alkylating agents are present in food and tobacco smoke, but are also used in cancer chemotherapy, inducing the DNA lesion O (6)-methylguanine. This critical adduct is repaired by O (6)-methylguanine-DNA methyltransferase (MGMT), resulting in MGMT inactivation and degradation. In the present study, we analyzed the effects of the natural disulfide compound lipoic acid (LA) on MGMT in vitro and in colorectal cancer cells. We show that LA, but not its reduced form dihydrolipoic acid, potently inhibits the activity of recombinant MGMT by interfering with its catalytic Cys-145 residue, which was partially reversible by N-acetyl cysteine. Incubation of HCT116 colorectal cancer cells with LA altered their glutathione pool and caused a decline in MGMT activity. This was mirrored by LA-induced depletion of MGMT protein, which was not attributable to changes in MGMT messenger RNA levels. Loss of MGMT protein coincided with LA-induced autophagy, a process resulting in lysosomal degradation of proteins, including presumably MGMT. LA-stimulated autophagy in a p53-independent manner as revealed by the response of isogenic HCT116 cell lines. Knockdown of the crucial autophagy component beclin-1 and chemical inhibitors blocked LA-induced autophagy, but did not abrogate LA-triggered MGMT degradation. Concomitant with MGMT depletion, LA pretreatment resulted in enhanced O (6)-methylguanine levels in DNA. It also increased the cytotoxicity of the alkylating anticancer drug temozolomide in temozolomide-resistant colorectal cancer cells. Taken together, our study showed that the natural compound LA inhibits MGMT and induces autophagy. Furthermore, LA enhanced the cytotoxic effects of temozolomide, which makes it a candidate for a supplement in cancer therapy.
Collapse
Affiliation(s)
- Anja Göder
- Department of Toxicology, University Medical Center Mainz, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany
| | - Georg Nagel
- Department of Toxicology, University Medical Center Mainz, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany
| | - Alexander Kraus
- Department of Toxicology, University Medical Center Mainz, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany
| | - Bastian Dörsam
- Department of Toxicology, University Medical Center Mainz, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany
| | - Nina Seiwert
- Department of Toxicology, University Medical Center Mainz, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany
| | - Bernd Kaina
- Department of Toxicology, University Medical Center Mainz, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany
| | - Jörg Fahrer
- Department of Toxicology, University Medical Center Mainz, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany
| |
Collapse
|
6
|
Abstract
Alkylating agents constitute a major class of frontline chemotherapeutic drugs that inflict cytotoxic DNA damage as their main mode of action, in addition to collateral mutagenic damage. Numerous cellular pathways, including direct DNA damage reversal, base excision repair (BER) and mismatch repair (MMR), respond to alkylation damage to defend against alkylation-induced cell death or mutation. However, maintaining a proper balance of activity both within and between these pathways is crucial for a favourable response of an organism to alkylating agents. Furthermore, the response of an individual to alkylating agents can vary considerably from tissue to tissue and from person to person, pointing to genetic and epigenetic mechanisms that modulate alkylating agent toxicity.
Collapse
Affiliation(s)
- Dragony Fu
- Departments of Biological Engineering and Biology, Center for Environmental Health Sciences, David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Jennifer A. Calvo
- Departments of Biological Engineering and Biology, Center for Environmental Health Sciences, David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Leona D Samson
- Departments of Biological Engineering and Biology, Center for Environmental Health Sciences, David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| |
Collapse
|
7
|
Kaina B, Margison GP, Christmann M. Targeting O⁶-methylguanine-DNA methyltransferase with specific inhibitors as a strategy in cancer therapy. Cell Mol Life Sci 2010; 67:3663-81. [PMID: 20717836 PMCID: PMC11115711 DOI: 10.1007/s00018-010-0491-7] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Accepted: 07/28/2010] [Indexed: 11/29/2022]
Abstract
O (6)-methylguanine-DNA methyltransferase (MGMT) repairs the cancer chemotherapy-relevant DNA adducts, O (6)-methylguanine and O (6)-chloroethylguanine, induced by methylating and chloroethylating anticancer drugs, respectively. These adducts are cytotoxic, and given the overwhelming evidence that MGMT is a key factor in resistance, strategies for inactivating MGMT have been pursued. A number of drugs have been shown to inactivate MGMT in cells, human tumour models and cancer patients, and O (6)-benzylguanine and O (6)-[4-bromothenyl]guanine have been used in clinical trials. While these agents show no side effects per se, they also inactivate MGMT in normal tissues and hence exacerbate the toxic side effects of the alkylating drugs, requiring dose reduction. This might explain why, in any of the reported trials, the outcome has not been improved by their inclusion. It is, however, anticipated that, with the availability of tumour targeting strategies and hematopoetic stem cell protection, MGMT inactivators hold promise for enhancing the effectiveness of alkylating agent chemotherapy.
Collapse
Affiliation(s)
- Bernd Kaina
- Institute of Toxicology, University Medical Center, Obere Zahlbacher Str. 67, 55131, Mainz, Germany.
| | | | | |
Collapse
|
8
|
Dahlmann HA, Vaidyanathan VG, Sturla SJ. Investigating the biochemical impact of DNA damage with structure-based probes: abasic sites, photodimers, alkylation adducts, and oxidative lesions. Biochemistry 2009; 48:9347-59. [PMID: 19757831 PMCID: PMC2789562 DOI: 10.1021/bi901059k] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
DNA sustains a wide variety of damage, such as the formation of abasic sites, pyrimidine dimers, alkylation adducts, or oxidative lesions, upon exposure to UV radiation, alkylating agents, or oxidative conditions. Since these forms of damage may be acutely toxic or mutagenic and potentially carcinogenic, it is of interest to gain insight into how their structures impact biochemical processing of DNA, such as synthesis, transcription, and repair. Lesion-specific molecular probes have been used to study polymerase-mediated translesion DNA synthesis of abasic sites and TT dimers, while other probes have been developed for specifically investigating the alkylation adduct O(6)-Bn-G and the oxidative lesion 8-oxo-G. In this review, recent examples of lesion-specific molecular probes are surveyed; their specificities of incorporation opposite target lesions compared to unmodified nucleotides are discussed, and limitations of their applications under physiologically relevant conditions are assessed.
Collapse
Affiliation(s)
| | | | - Shana J. Sturla
- To whom correspondence should be addressed: ; Phone: 612-626-0496; Fax: 612-624-0139
| |
Collapse
|
9
|
O(6)-methylguanine-DNA methyltransferase depletion and DNA damage in patients with melanoma treated with temozolomide alone or with lomeguatrib. Br J Cancer 2009; 100:1250-6. [PMID: 19367283 PMCID: PMC2676560 DOI: 10.1038/sj.bjc.6605015] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
We evaluated the pharmacodynamic effects of the O6-methylguanine-DNA methyltransferase (MGMT) inactivator lomeguatrib (LM) on patients with melanoma in two clinical trials. Patients received temozolomide (TMZ) for 5 days either alone or with LM for 5, 10 or 14 days. Peripheral blood mononuclear cells (PBMCs) were isolated before treatment and during cycle 1. Where available, tumour biopsies were obtained after the last drug dose in cycle 1. Samples were assayed for MGMT activity, total MGMT protein, and O6-methylguanine (O6-meG) and N7-methylguanine levels in DNA. MGMT was completely inactivated in PBMC from patients receiving LM, but detectable in those on TMZ alone. Tumours biopsied on the last day of treatment showed complete inactivation of MGMT but there was recovery of activity in tumours sampled later. Significantly more O6-meG was present in the PBMC DNA of LM/TMZ patients than those on TMZ alone. LM/TMZ leads to greater MGMT inactivation, and higher levels of O6-meG than TMZ alone. Early recovery of MGMT activity in tumours suggested that more protracted dosing with LM is required. Extended dosing of LM completely inactivated PBMC MGMT, and resulted in persistent levels of O6-meG in PBMC DNA during treatment.
Collapse
|
10
|
Yang CG, Garcia K, He C. Damage detection and base flipping in direct DNA alkylation repair. Chembiochem 2009; 10:417-23. [PMID: 19145606 DOI: 10.1002/cbic.200800580] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
THE FOREIGN LESION: The mechanistic questions for DNA base damage detection by repair proteins are discussed in this Minireview. Repair proteins could either probe and locate a weakened base pair that results from base damage, or passively capture an extrahelical base lesion in the first step of damage searching on double-stranded DNA. How some repair proteins, such as AGT (see figure), locate base lesions in DNA is still not fully understood.To remove a few damaged bases efficiently from the context of the entire genome, the DNA base repair proteins rely on remarkably specific detection mechanisms to locate base lesions. This efficient molecular recognition event inside cells has been extensively studied with various structural and biochemical tools. These studies suggest that DNA base damage can be located by repair proteins by using two mechanisms: a repair protein can probe and detect a weakened base pair that results from mutagenic or cytotoxic base damage; alternatively, a protein can passively capture and stabilize an extrahelical base lesion. Our chemical and structural studies on the direct DNA repair proteins hAGT, C-Ada and ABH2 suggest that these proteins search for weakened base pairs in their first step of damage searching. We have also discovered a very unique base-flipping mechanism used by the DNA repair protein AlkB. This protein distorts DNA and favors single stranded DNA (ssDNA) substrates over double-stranded (dsDNA) ones. Potentially, it locates base lesions in dsDNA by imposing a constraint that targets less rigid regions of the duplex DNA. The exact mechanism of how AlkB and related proteins search for damage in ssDNA and dsDNA still awaits further studies.
Collapse
Affiliation(s)
- Cai-Guang Yang
- Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | | | | |
Collapse
|
11
|
Doak SH, Brüsehafer K, Dudley E, Quick E, Johnson G, Newton RP, Jenkins GJS. No-observed effect levels are associated with up-regulation of MGMT following MMS exposure. Mutat Res 2008; 648:9-14. [PMID: 18992265 DOI: 10.1016/j.mrfmmm.2008.09.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 07/31/2008] [Accepted: 09/04/2008] [Indexed: 05/27/2023]
Abstract
The alkylating agents methyl methanesulphonate (MMS) and ethyl methanesulphonate (EMS) have non-linear dose-response curves, with a no-observed effect level (NOEL) and a lowest observed effect level (LOEL) for both gross chromosomal damage and mutagenicity. However, the biological mechanism responsible for the NOEL has yet to be identified. A strong candidate is DNA repair as it may be able to efficiently remove alkyl adducts at low doses resulting in a NOEL, but at higher doses fails to fully remove all lesions due to saturation of enzymatic activity resulting in a LOEL and subsequent linear increases in mutagenicity. We therefore assessed the transcriptional status of N-methylpurine-DNA glycoslase (MPG) and O(6)-methylguanine DNA methyltransferase (MGMT), which represent the first line of defence following exposure to alkylating agents through the respective enzymatic removal of N7-alkylG and O(6)-alkylG. The relative MPG and MGMT gene expression profiles were assessed by real-time RT-PCR following exposure to 0-2 microg/ml MMS for 1-24h. MPG expression remained fairly steady, but in contrast significant up-regulation of MGMT was observed when cells were treated with 0.5 and 1.0 microg/ml MMS for 4h (2.5- and 6.5-fold increases respectively). These doses lie within the NOEL for MMS mutagenicity (LOEL is 1.25 microg/ml), thus this boost in MGMT expression at low doses may be responsible for efficiently repairing O(6)methylG lesions and creating the non-linear response for mutations. However, as the LOEL for MMS clastogenicity is 0.85 microg/ml, O(6)-alkylG is unlikely to be responsible for the clastogenicity observed at these concentrations. Consequently, at low doses N7-methylG is possibly the predominant cause of MMS clastogenicity, while O(6)-methylG is more likely to be responsible for MMS mutagenicity, with MGMT up-regulation playing a key role in removal of O(6)-alkylG lesions before they are fixed as permanent point mutations, resulting in non-linear dose-responses for direct acting genotoxins.
Collapse
Affiliation(s)
- Shareen H Doak
- Institute of Life Science, School of Medicine, Swansea University, Singleton Park, Swansea, Wales, UK.
| | | | | | | | | | | | | |
Collapse
|
12
|
Kaina B, Christmann M, Naumann S, Roos WP. MGMT: key node in the battle against genotoxicity, carcinogenicity and apoptosis induced by alkylating agents. DNA Repair (Amst) 2007; 6:1079-99. [PMID: 17485253 DOI: 10.1016/j.dnarep.2007.03.008] [Citation(s) in RCA: 444] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
O(6)-methylguanine-DNA methyltransferase (MGMT) plays a crucial role in the defense against alkylating agents that generate, among other lesions, O(6)-alkylguanine in DNA (collectively termed O(6)-alkylating agents [O(6)AA]). The defense is highly important, since O(6)AA are common environmental carcinogens, are formed endogenously during normal cellular metabolism and possibly inflammation, and are being used in cancer therapy. O(6)AA induced DNA damage is subject to repair, which is executed by MGMT, AlkB homologous proteins (ABH) and base excision repair (BER). Although this review focuses on MGMT, the mechanism of repair by ABH and BER will also be discussed. Experimental systems, in which MGMT has been modulated, revealed that O(6)-methylguanine (O(6)MeG) and O(6)-chloroethylguanine are major mutagenic, carcinogenic, recombinogenic, clastogenic and killing lesions. O(6)MeG-induced clastogenicity and cell death require MutS alpha-dependent mismatch repair (MMR), whereas O(6)-chloroethylguanine-induced killing occurs independently of MMR. Extensive DNA replication is required for O(6)MeG to provoke cytotoxicity. In MGMT depleted cells, O(6)MeG induces apoptosis almost exclusively, barely any necrosis, which is presumably due to the remarkable ability of secondarily formed DNA double-strand breaks (DSBs) to trigger apoptosis via ATM/ATR, Chk1, Chk2, p53 and p73. Depending on the cellular background, O(6)MeG activates both the death receptor and the mitochondrial apoptotic pathway. The inter-individual expression of MGMT in human lymphocytes is highly variable. Given the key role of MGMT in cellular defense, determination of MGMT activity could be useful for assessing a patient's drug sensitivity. MGMT is expressed at highly variable amounts in human tumors. In gliomas, a correlation was found between MGMT activity, MGMT promoter methylation and response to O(6)AA. Although the human MGMT gene is inducible by glucocorticoids and genotoxins such as radiation and alkylating agents, the role of this induction in the protection against carcinogens and the development of chemotherapeutic alkylating drug resistance are still unclear. Modulation of MGMT expression in tumors and normal tissue is currently being investigated as a possible strategy for improving cancer therapy.
Collapse
Affiliation(s)
- Bernd Kaina
- Department of Toxicology, University of Mainz, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany.
| | | | | | | |
Collapse
|
13
|
Ahn JM, Kim BC, Gu MB. Characterization ofgltA: luxCDABE fusion inEscherichia coli as a toxicity biosensor. BIOTECHNOL BIOPROC E 2006. [DOI: 10.1007/bf02932076] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
14
|
Pan S, Sun X, Lee JK. DNA stability in the gas versus solution phases: a systematic study of thirty-one duplexes with varying length, sequence, and charge level. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2006; 17:1383-1395. [PMID: 16914323 DOI: 10.1016/j.jasms.2006.07.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2006] [Revised: 07/21/2006] [Accepted: 07/21/2006] [Indexed: 05/11/2023]
Abstract
We report herein a systematic mass spectrometric study of a series of thirty-one non-self-complementary, matched, DNA duplexes ranging in size from 5- to 12-mers. The purpose of this work is threefold: (1) to establish the viability of using mass spectrometry as a tool for examining solution phase stabilities of DNA duplexes; (2) to systematically assess gas-phase stabilities of DNA duplexes; and (3) to compare gas and solution phase stabilities in an effort to understand how media affects DNA stability. These fundamental issues are of importance both on their own, and also for harnessing the potential of mass spectrometry for biological applications. We have found that ion abundances do not always track with solution phase stability; GC content must be taken into account. Two duplexes with the same Tm yet with differing GC content can yield different ion abundances. That is, if two duplexes have the exact same melting temperature, yet one has a higher GC content, the duplex with the higher GC content yields a higher ion abundance. It thus appears that not only is a GC base pair stronger than an AT base pair, but the relative strengths of each differ in the gas phase versus in solution, such that the electrospray process can differentiate between them. We also characterize the gas-phase stabilities of the duplexes, using collision-induced dissociation (CID) as a method to assess stability. We focus on two aspects of this CID experiment. One, we examine what factors appear to control whether the duplexes dissociate into single strands or covalently fragment; we are able to utilize a charge state normalization we coin "charge level" to compare our results with others' and establish generalities regarding dissociation versus fragmentation patterns. Two, we examine those duplexes that primarily dissociate and use CID to assess the gas-phase stabilities. We find that correlation of gas-phase to solution-phase stabilities is more likely to occur when duplexes of varying GC content are examined. Duplexes with the same GC content tend to have stabilities that do not parallel those in solution. We discuss these results in light of the different roles that hydrogen bonding and base stacking play in solution versus the gas phase. Ultimately, we apply what we learn to lend insight into the biological problem of how the carcinogenic, damaged nucleobase O6-methylguanine causes mutations.
Collapse
Affiliation(s)
- Su Pan
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 08854, Piscataway, NJ, USA
| | - Xuejun Sun
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 08854, Piscataway, NJ, USA
| | - Jeehiun K Lee
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 08854, Piscataway, NJ, USA.
| |
Collapse
|
15
|
Roberts A, Pelton JG, Wemmer DE. Structural studies of MJ1529, an O6-methylguanine-DNA methyltransferase. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2006; 44 Spec No:S71-82. [PMID: 16826543 DOI: 10.1002/mrc.1823] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The structure of an O6-methylguanine-DNA methyltransferase (MGMT) from the thermophile Methanococcus jannaschii has been determined using multinuclear multidimensional NMR spectroscopy. The structure is similar to homologs from other organisms that have been determined by crystallography, with some variation in the N-terminal domain. The C-terminal domain is more highly conserved in both sequence and structure. Regions of the protein show broadening, reflecting conformational flexibility that is likely related to function.
Collapse
Affiliation(s)
- Anne Roberts
- Department of Chemistry, University of California and Physical Biosciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720-1460, USA
| | | | | |
Collapse
|
16
|
Affiliation(s)
- Yukiko Mishina
- Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637
| | - Erica M. Duguid
- Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637
| | - Chuan He
- Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637
| |
Collapse
|
17
|
Bobola MS, Silber JR, Ellenbogen RG, Geyer JR, Blank A, Goff RD. O6-methylguanine-DNA methyltransferase, O6-benzylguanine, and resistance to clinical alkylators in pediatric primary brain tumor cell lines. Clin Cancer Res 2005; 11:2747-55. [PMID: 15814657 DOI: 10.1158/1078-0432.ccr-04-2045] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Primary brain tumors are the leading cause of cancer death in children. Our purpose is (a) to assess the contribution of the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) to the resistance of pediatric brain tumor cell lines to clinical alkylating agents and (b) to evaluate variables for maximal potentiation of cell killing by the MGMT inhibitor O6-benzylguanine, currently in clinical trials. Few such data for pediatric glioma lines, particularly those from low-grade tumors, are currently available. EXPERIMENTAL DESIGN We used clonogenic assays of proliferative survival to quantitate cytoxicity of the chloroethylating agent 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and the methylating agent temozolomide in 11 glioma and five medulloblastoma lines. Twelve lines are newly established and characterized here, nine of them from low-grade gliomas including pilocytic astrocytomas. RESULTS (a) MGMT is a major determinant of BCNU resistance and the predominant determinant of temozolomide resistance in both our glioma and medulloblastoma lines. On average, O(6)-benzylguanine reduced LD10 for BCNU and temozolomide, 2.6- and 26-fold, respectively, in 15 MGMT-expressing lines. (b) O6-Benzylguanine reduced DT (the threshold dose for killing) for BCNU and temozolomide, 3.3- and 138-fold, respectively. DT was decreased from levels higher than, to levels below, clinically achievable plasma doses for both alkylators. (c) Maximal potentiation by O6-benzylguanine required complete and prolonged suppression of MGMT. CONCLUSIONS Our results support the use of O6-benzylguanine to achieve full benefit of alkylating agents, particularly temozolomide, in the chemotherapy of pediatric brain tumors.
Collapse
Affiliation(s)
- Michael S Bobola
- Division of Neurosurgery, Department of Surgery and Hematology/Oncology, Children's Hospital and Regional Medical Center, Seattle, Washington 98105, USA.
| | | | | | | | | | | |
Collapse
|
18
|
Kaina B. DNA damage-triggered apoptosis: critical role of DNA repair, double-strand breaks, cell proliferation and signaling. Biochem Pharmacol 2003; 66:1547-54. [PMID: 14555233 DOI: 10.1016/s0006-2952(03)00510-0] [Citation(s) in RCA: 219] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Genotoxic DNA damaging agents may activate both membrane death receptors and the endogenous mitochondrial damage pathway leading to cell death via apoptosis. Here, apoptotic responses in cells exhibiting a defect in various DNA repair pathways such as alkyltransferase, base excision repair, nucleotide excision repair and mismatch repair are reviewed. The HSVTk/ganciclovir and VZV/BVDU suicide system will also be discussed. Data are available to show that critical DNA damage triggers apoptosis in a DNA replication dependent way by activating the mitochondrial damage pathway in fibroblasts. It is proposed that DNA double-strand breaks (DSBs) are common ultimate apoptosis-triggering lesions arising from primary DNA lesions during DNA replication. Thus, DNA replication is a necessary component in DNA damage-triggered apoptosis, at least in fibroblasts treated with genotoxins not inducing DSBs themselves. For methylating agents inducing O(6)-methylguanine, an additional requirement is mismatch repair provoking DSB formation that triggers Bcl-2 decline and caspase-9/-3 activation. This occurs independent of p53 since most of the repair deficient cell lines under study were mutated for p53. Moreover, p53 knockout fibroblasts are more sensitive to methylating agents and UV light than p53 wt cells, suggesting p53 to play a protective rather than a pro-apoptotic role in this cell system, probably by its involvement in DNA repair. However, for lymphoblastoid cells p53 wt variants are more sensitive to DNA damage indicating that p53 participates in apoptotic signaling in a cell type-specific fashion. The role of topoisomerase II inhibitors and c-Fos/AP-1 in apoptosis will also be discussed.
Collapse
Affiliation(s)
- Bernd Kaina
- Division of Applied Toxicology, Institute of Toxicology, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany.
| |
Collapse
|
19
|
Abstract
AIMS The aim of this study is to understand different adaptive responses in bacteria caused by three different mutagens, namely, an intercalating agent, an alkylating agent and a hydroxylating agent, and the repair systems according to the type of DNA damage, that is, DNA cross-linking and delayed DNA synthesis, alkylation and hydroxylation of DNA. A recombinant bioluminescent Escherichia coli, DPD2794 with the recA promoter fused to luxCDABE originating from Vibrio fischeri, was used in this study. METHODS AND RESULTS The recombinant bioluminescent E. coli strain DPD2794, containing a recA promoter fused to luxCDABE from V. fischeri, was used to detect adaptive and repair responses to DNA damage caused by mitomycin C (MMC), and these responses were compared with those when the cells were induced with N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and hydrogen peroxide (H2O2). The response ratio between the induced samples and that of the controls decreased suddenly when the induced culture was used in further inductions, indicating a possible adaptive response to DNA damage. DNA damage, or the proteins produced, because of MMC addition does not appear to be completely resolved until the seventh sub-culture after the initial induction, whereas simple damage, such as the base modification caused by MNNG and H2O2, appears to be repaired rapidly as evidenced by the quick recovery of sensitivity. CONCLUSIONS These results suggest that it takes more time to completely repair DNA damage caused by MMC, as compared with a simple repair such as that required for the damage caused by MNNG and H2O2. Therefore, repair of the damage caused by these three mutagens is controlled by different regulons, even though they all induced the recA promoter. SIGNIFICANCE AND IMPACT OF THE STUDY Using a bioluminescent E. coli harbouring a recA promoter-lux fusion, it was found that different adaptive responses and repair systems for DNA damage caused by several mutagens exists in E. coli.
Collapse
Affiliation(s)
- J Min
- National Research Laboratory on Environmental Biotechnology, Kwangju Institute of Science and Technology, Kwangju, South Korea
| | | |
Collapse
|
20
|
Duguid EM, Mishina Y, He C. How Do DNA Repair Proteins Locate Potential Base Lesions? A Chemical Crosslinking Method to Investigate O6-Alkylguanine-DNA Alkyltransferases. ACTA ACUST UNITED AC 2003; 10:827-35. [PMID: 14522053 DOI: 10.1016/j.chembiol.2003.08.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
O(6)-alkylguanine-DNA alkyltransferases directly reverse the alkylation on the O(6) position of guanine in DNA. This group of proteins has been proposed to repair the damaged base in an extrahelical manner; however, the detailed mechanism is not understood. Here we applied a chemical disulfide crosslinking method to probe the damage-searching mechanism of two O(6)-alkylguanine-DNA alkyltransferases, the Escherichia coli C-Ada and the human AGT. Crosslinking reactions with different efficiency occur between the reactive Cys residues of both proteins and a modified cytosine bearing a thiol tether in various DNA probes. Our results indicate that it is not necessary for these proteins to actively flip out every base to find damage. Instead they can locate potential lesions by simply capturing a lesioned base that is transiently extrahelical or sensing the unstable nature of a damaged base pair.
Collapse
Affiliation(s)
- Erica M Duguid
- Department of Chemistry, University of Chicago, 5735 South Ellis Avenue, Chicago, IL 60637, USA
| | | | | |
Collapse
|