1
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Thuresson A, Brazina J, Akram T, Albrecht J, Dahl N, Soussi Zander C, Caldecott KW. Novel PNKP mutations associated with reduced DNA single-strand break repair and severe microcephaly, seizures, and developmental delay. Mol Genet Genomic Med 2024; 12:e2295. [PMID: 37916443 PMCID: PMC10767416 DOI: 10.1002/mgg3.2295] [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: 03/16/2023] [Revised: 08/18/2023] [Accepted: 09/19/2023] [Indexed: 11/03/2023] Open
Abstract
BACKGROUND Microcephaly with early-onset seizures (MCSZ) is a neurodevelopmental disorder caused by pathogenic variants in the DNA strand break repair protein, polynucleotide kinase 3'-phosphatase (PNKP). METHODS We have used whole genome sequencing and Sanger sequencing to identify disease-causing variants, followed by a minigene assay, Western blotting, alkaline comet assay, γH2AX, and ADP-ribose immunofluorescence. RESULTS Here, we describe a patient with compound heterozygous variants in PNKP, including a missense variant in the DNA phosphatase domain (T323M) and a novel splice acceptor site variant within the DNA kinase domain that we show leads to exon skipping. We show that primary fibroblasts derived from the patient exhibit greatly reduced levels of PNKP protein and reduced rates of DNA single-strand break repair, confirming that the mutated PNKP alleles are dysfunctional. CONCLUSION The data presented show that the detected compound heterozygous variants result in reduced levels of PNKP protein, which affect the repair of both oxidative and TOP1-induced single-strand breaks, and most likely causes MCSZ in this patient.
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Affiliation(s)
- Ann‐Charlotte Thuresson
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory UppsalaUppsala UniversityUppsalaSweden
| | - Jan Brazina
- Genome Damage and Stability CentreUniversity of SussexBrightonUK
| | - Talia Akram
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory UppsalaUppsala UniversityUppsalaSweden
- Present address:
Departments of Pediatrics, Neurology and PhysiologyNorthwestern University Feinberg School of Medicine, Ann & Robert H. Lurie Children's Hospital of ChicagoChicagoIllinoisUSA
| | | | - Niklas Dahl
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory UppsalaUppsala UniversityUppsalaSweden
| | - Cecilia Soussi Zander
- Department of Immunology, Genetics and Pathology, Science for Life Laboratory UppsalaUppsala UniversityUppsalaSweden
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2
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Jha JS, Yin J, Haldar T, Wang Y, Gates KS. Reconsidering the Chemical Nature of Strand Breaks Derived from Abasic Sites in Cellular DNA: Evidence for 3'-Glutathionylation. J Am Chem Soc 2022; 144:10471-10482. [PMID: 35612610 DOI: 10.1021/jacs.2c02703] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The hydrolytic loss of coding bases from cellular DNA is a common and unavoidable reaction. The resulting abasic sites can undergo β-elimination of the 3'-phosphoryl group to generate a strand break with an electrophilic α,β-unsaturated aldehyde residue on the 3'-terminus. The work reported here provides evidence that the thiol residue of the cellular tripeptide glutathione rapidly adds to the alkenal group on the 3'-terminus of an AP-derived strand break. The resulting glutathionylated adduct is the only major cleavage product observed when β-elimination occurs at an AP site in the presence of glutathione. Formation of the glutathionylated cleavage product is reversible, but in the presence of physiological concentrations of glutathione, the adduct persists for days. Biochemical experiments provided evidence that the 3'-phosphodiesterase activity of the enzyme apurinic/apyrimidinic endonuclease (APE1) can remove the glutathionylated sugar remnant from an AP-derived strand break to generate the 3'OH residue required for repair via base excision or single-strand break repair pathways. The results suggest that a previously unrecognized 3'glutathionylated sugar remnant─and not the canonical α,β-unsaturated aldehyde end group─may be the true strand cleavage product arising from β-elimination at an abasic site in cellular DNA. This work introduces the 3'glutathionylated cleavage product as the major blocking group that must be trimmed to enable repair of abasic site-derived strand breaks by the base excision repair or single-strand break repair pathways.
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3
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Jiang B, Murray C, Cole BL, Glover JNM, Chan GK, Deschenes J, Mani RS, Subedi S, Nerva JD, Wang AC, Lockwood CM, Mefford HC, Leary SES, Ojemann JG, Weinfeld M, Ene CI. Mutations of the DNA repair gene PNKP in a patient with microcephaly, seizures, and developmental delay (MCSZ) presenting with a high-grade brain tumor. Sci Rep 2022; 12:5386. [PMID: 35354845 PMCID: PMC8967877 DOI: 10.1038/s41598-022-09097-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Accepted: 03/04/2022] [Indexed: 11/08/2022] Open
Abstract
Polynucleotide Kinase-Phosphatase (PNKP) is a bifunctional enzyme that possesses both DNA 3'-phosphatase and DNA 5'-kinase activities, which are required for processing termini of single- and double-strand breaks generated by reactive oxygen species (ROS), ionizing radiation and topoisomerase I poisons. Even though PNKP is central to DNA repair, there have been no reports linking PNKP mutations in a Microcephaly, Seizures, and Developmental Delay (MSCZ) patient to cancer. Here, we characterized the biochemical significance of 2 germ-line point mutations in the PNKP gene of a 3-year old male with MSCZ who presented with a high-grade brain tumor (glioblastoma multiforme) within the cerebellum. Functional and biochemical studies demonstrated these PNKP mutations significantly diminished DNA kinase/phosphatase activities, altered its cellular distribution, caused defective repair of DNA single/double stranded breaks, and were associated with a higher propensity for oncogenic transformation. Our findings indicate that specific PNKP mutations may contribute to tumor initiation within susceptible cells in the CNS by limiting DNA damage repair and increasing rates of spontaneous mutations resulting in pediatric glioma associated driver mutations such as ATRX and TP53.
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Affiliation(s)
- Bingcheng Jiang
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, AB, T6G 1Z2, Canada
| | - Cameron Murray
- Department of Biochemistry, University of Alberta, Medical Sciences Building, Edmonton, AB, T6G 2H7, Canada
| | - Bonnie L Cole
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - J N Mark Glover
- Department of Biochemistry, University of Alberta, Medical Sciences Building, Edmonton, AB, T6G 2H7, Canada
| | - Gordon K Chan
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, AB, T6G 1Z2, Canada
| | - Jean Deschenes
- Department of Laboratory Medicine and Pathology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, AB, T6G 1Z2, Canada
| | - Rajam S Mani
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, AB, T6G 1Z2, Canada
| | - Sudip Subedi
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, AB, T6G 1Z2, Canada
| | - John D Nerva
- Department of Neurological Surgery, Tulane University, New Orleans, LA, USA
| | - Anthony C Wang
- Department of Neurological Surgery, University of California Los Angeles, Los Angeles, CA, USA
| | | | - Heather C Mefford
- Division of Genetics Medicine, University of Washington, Seattle, WA, USA
| | - Sarah E S Leary
- Division of Pediatric Hematology/Oncology, Seattle Children's Hospital, Seattle, WA, USA
| | - Jeffery G Ojemann
- Department of Neurological Surgery, University of Washington, Seattle, WA, USA
| | - Michael Weinfeld
- Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, AB, T6G 1Z2, Canada.
| | - Chibawanye I Ene
- Department of Neurological Surgery, MD Anderson Cancer Center, Houston, TX, USA.
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4
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Crewe M, Madabhushi R. Topoisomerase-Mediated DNA Damage in Neurological Disorders. Front Aging Neurosci 2021; 13:751742. [PMID: 34899270 PMCID: PMC8656403 DOI: 10.3389/fnagi.2021.751742] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Accepted: 10/23/2021] [Indexed: 12/12/2022] Open
Abstract
The nervous system is vulnerable to genomic instability and mutations in DNA damage response factors lead to numerous developmental and progressive neurological disorders. Despite this, the sources and mechanisms of DNA damage that are most relevant to the development of neuronal dysfunction are poorly understood. The identification of primarily neurological abnormalities in patients with mutations in TDP1 and TDP2 suggest that topoisomerase-mediated DNA damage could be an important underlying source of neuronal dysfunction. Here we review the potential sources of topoisomerase-induced DNA damage in neurons, describe the cellular mechanisms that have evolved to repair such damage, and discuss the importance of these repair mechanisms for preventing neurological disorders.
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5
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Prenatal phenotype of PNKP-related primary microcephaly associated with variants affecting both the FHA and phosphatase domain. Eur J Hum Genet 2021; 30:101-110. [PMID: 34697416 PMCID: PMC8738728 DOI: 10.1038/s41431-021-00982-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 09/05/2021] [Accepted: 10/04/2021] [Indexed: 11/20/2022] Open
Abstract
Biallelic PNKP variants cause heterogeneous disorders ranging from neurodevelopmental disorder with microcephaly/seizures to adult-onset Charcot–Marie–Tooth disease. To date, only postnatal descriptions exist. We present the first prenatal diagnosis of PNKP-related primary microcephaly. Pathological examination of a male fetus in the 18th gestational week revealed micrencephaly with extracerebral malformations and thus presumed syndromic microcephaly. A recessive disorder was suspected because of previous pregnancy termination for similar abnormalities. Prenatal trio-exome sequencing identified compound heterozygosity for the PNKP variants c.498G>A, p.[(=),0?] and c.302C>T, p.(Pro101Leu). Segregation confirmed both variants in the sister fetus. Through RNA analyses, we characterized exon 4 skipping affecting the PNKP forkhead-associated (FHA) and phosphatase domains (p.Leu67_Lys166del) as the predominant effect of the paternal c.498G>A variant. We retrospectively investigated two unrelated individuals diagnosed with biallelic PNKP-variants to compare prenatal/postnatal phenotypes. Both carry the splice donor variant c.1029+2T>C intrans with a variant in the FHA domain (c.311T>C, p.(Leu104Pro); c.151G>C, p.(Val51Leu)). RNA-seq showed complex splicing for c.1029+2T>C and c.151G>C. Structural modeling revealed significant clustering of missense variants in the FHA domain with variants generating structural damage. Our clinical description extends the PNKP-continuum to the prenatal stage. Investigating possible PNKP-variant effects using RNA and structural modeling, we highlight the mutational complexity and exemplify a PNKP-variant characterization framework.
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6
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Shin W, Alpaugh W, Hallihan LJ, Sinha S, Crowther E, Martin GR, Scheidl-Yee T, Yang X, Yoon G, Goldsmith T, Berger ND, de Almeida LG, Dufour A, Dobrinski I, Weinfeld M, Jirik FR, Biernaskie J. PNKP is required for maintaining the integrity of progenitor cell populations in adult mice. Life Sci Alliance 2021; 4:4/9/e202000790. [PMID: 34226276 PMCID: PMC8321660 DOI: 10.26508/lsa.202000790] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 06/22/2021] [Accepted: 06/23/2021] [Indexed: 11/24/2022] Open
Abstract
Knockout of Pnkp in adult mice impairs the growth of hair follicle, spermatogonial, and neural progenitor populations. DNA repair proteins are critical to the maintenance of genomic integrity. Specific types of genotoxic factors, including reactive oxygen species generated during normal cellular metabolism or as a result of exposure to exogenous oxidative agents, frequently leads to “ragged” single-strand DNA breaks. The latter exhibits abnormal free DNA ends containing either a 5′-hydroxyl or 3′-phosphate requiring correction by the dual function enzyme, polynucleotide kinase phosphatase (PNKP), before DNA polymerase and ligation reactions can occur to seal the break. Pnkp gene deletion during early murine development leads to lethality; in contrast, the role of PNKP in adult mice is unknown. To investigate the latter, we used an inducible conditional mutagenesis approach to cause global disruption of the Pnkp gene in adult mice. This resulted in a premature aging-like phenotype, characterized by impaired growth of hair follicles, seminiferous tubules, and neural progenitor cell populations. These results point to an important role for PNKP in maintaining the normal growth and survival of these murine progenitor populations.
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Affiliation(s)
- Wisoo Shin
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada
| | - Whitney Alpaugh
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada
| | - Laura J Hallihan
- McCaig Institute for Bone and Joint Health, Calgary, Canada.,Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Canada
| | - Sarthak Sinha
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada
| | - Emilie Crowther
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada
| | - Gary R Martin
- McCaig Institute for Bone and Joint Health, Calgary, Canada.,Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Canada
| | | | - Xiaoyan Yang
- Department of Oncology, University of Alberta, and Cross Cancer Institute, Edmonton, Canada
| | - Grace Yoon
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada
| | - Taylor Goldsmith
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada
| | - Nelson D Berger
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Canada
| | - Luiz Gn de Almeida
- McCaig Institute for Bone and Joint Health, Calgary, Canada.,Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Canada
| | - Antoine Dufour
- McCaig Institute for Bone and Joint Health, Calgary, Canada.,Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Canada.,Department of Physiology and Pharmacology, University of Calgary, Calgary, Canada
| | - Ina Dobrinski
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada
| | - Michael Weinfeld
- Department of Oncology, University of Alberta, and Cross Cancer Institute, Edmonton, Canada
| | - Frank R Jirik
- McCaig Institute for Bone and Joint Health, Calgary, Canada .,Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Canada.,Alberta Children's Hospital Research Institute, Calgary, Canada
| | - Jeff Biernaskie
- Department of Comparative Biology and Experimental Medicine, University of Calgary, Calgary, Canada .,Department of Physiology and Pharmacology, University of Calgary, Calgary, Canada.,Department of Surgery, University of Calgary, Calgary, Canada.,Hotchkiss Brain Institute, Calgary, Canada
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7
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Bermúdez-Guzmán L, Jimenez-Huezo G, Arguedas A, Leal A. Mutational survivorship bias: The case of PNKP. PLoS One 2020; 15:e0237682. [PMID: 33332469 PMCID: PMC7746193 DOI: 10.1371/journal.pone.0237682] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 11/23/2020] [Indexed: 01/21/2023] Open
Abstract
The molecular function of a protein relies on its structure. Understanding how variants alter structure and function in multidomain proteins is key to elucidate the generation of a pathological phenotype. However, one may fall into the logical bias of assessing protein damage only based on the variants that are visible (survivorship bias), which can lead to partial conclusions. This is the case of PNKP, an important nuclear and mitochondrial DNA repair enzyme with both kinase and phosphatase function. Most variants in PNKP are confined to the kinase domain, leading to a pathological spectrum of three apparently distinct clinical entities. Since proteins and domains may have a different tolerability to variation, we evaluated whether variants in PNKP are under survivorship bias. Here, we provide the evidence that supports a higher tolerance in the kinase domain even when all variants reported are deleterious. Instead, the phosphatase domain is less tolerant due to its lower variant rates, a higher degree of sequence conservation, lower dN/dS ratios, and the presence of more disease-propensity hotspots. Together, our results support previous experimental evidence that demonstrated that the phosphatase domain is functionally more necessary and relevant for DNA repair, especially in the context of the development of the central nervous system. Finally, we propose the term "Wald’s domain" for future studies analyzing the possible survivorship bias in multidomain proteins.
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Affiliation(s)
- Luis Bermúdez-Guzmán
- Section of Genetics and Biotechnology, School of Biology, University de Costa Rica, San Pedro, San José, Costa Rica
| | - Gabriel Jimenez-Huezo
- Section of Genetics and Biotechnology, School of Biology, University de Costa Rica, San Pedro, San José, Costa Rica
| | - Andrés Arguedas
- School of Statistics, University de Costa Rica, San Pedro, San José, Costa Rica
| | - Alejandro Leal
- Section of Genetics and Biotechnology, School of Biology, University de Costa Rica, San Pedro, San José, Costa Rica
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8
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The FHA domain of PNKP is essential for its recruitment to DNA damage sites and maintenance of genome stability. Mutat Res 2020; 822:111727. [PMID: 33220551 DOI: 10.1016/j.mrfmmm.2020.111727] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 09/28/2020] [Accepted: 10/26/2020] [Indexed: 01/08/2023]
Abstract
Polynucleotide kinase phosphatase (PNKP) has dual enzymatic activities as kinase and phosphatase for DNA ends, which are the prerequisite for the ligation, and thus is involved in base excision repair, single-strand break repair and non-homologous end joining for double-strand break (DSB) repair. In this study, we examined mechanisms for the recruitment of PNKP to DNA damage sites by laser micro-irradiation and live-cell imaging analysis using confocal microscope. We show that the forkhead-associated (FHA) domain of PNKP is essential for the recruitment of PNKP to DNA damage sites. Arg35 and Arg48 within the FHA domain are required for interactions with XRCC1 and XRCC4. PNKP R35A/R48A mutant failed to accumulate on the laser track and siRNA-mediated depletion of XRCC1 and/or XRCC4 reduced PNKP accumulation on the laser track, indicating that PNKP is recruited to DNA damage sites via the interactions between its FHA domain and XRCC1 or XRCC4. Furthermore, cells expressing PNKP R35A/R48A mutant exhibited increased sensitivity toward ionizing radiation in association with delayed SSB and DSB repair and genome instability, represented by micronuclei and chromosome bridges. Taken together, these findings revealed the importance of PNKP recruitment to DNA damage sites via its FHA domain for DNA repair and maintenance of genome stability.
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9
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Kalasova I, Hailstone R, Bublitz J, Bogantes J, Hofmann W, Leal A, Hanzlikova H, Caldecott KW. Pathological mutations in PNKP trigger defects in DNA single-strand break repair but not DNA double-strand break repair. Nucleic Acids Res 2020; 48:6672-6684. [PMID: 32504494 PMCID: PMC7337934 DOI: 10.1093/nar/gkaa489] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 04/30/2020] [Accepted: 06/04/2020] [Indexed: 12/20/2022] Open
Abstract
Hereditary mutations in polynucleotide kinase-phosphatase (PNKP) result in a spectrum of neurological pathologies ranging from neurodevelopmental dysfunction in microcephaly with early onset seizures (MCSZ) to neurodegeneration in ataxia oculomotor apraxia-4 (AOA4) and Charcot-Marie-Tooth disease (CMT2B2). Consistent with this, PNKP is implicated in the repair of both DNA single-strand breaks (SSBs) and DNA double-strand breaks (DSBs); lesions that can trigger neurodegeneration and neurodevelopmental dysfunction, respectively. Surprisingly, however, we did not detect a significant defect in DSB repair (DSBR) in primary fibroblasts from PNKP patients spanning the spectrum of PNKP-mutated pathologies. In contrast, the rate of SSB repair (SSBR) is markedly reduced. Moreover, we show that the restoration of SSBR in patient fibroblasts collectively requires both the DNA kinase and DNA phosphatase activities of PNKP, and the fork-head associated (FHA) domain that interacts with the SSBR protein, XRCC1. Notably, however, the two enzymatic activities of PNKP appear to affect different aspects of disease pathology, with reduced DNA phosphatase activity correlating with neurodevelopmental dysfunction and reduced DNA kinase activity correlating with neurodegeneration. In summary, these data implicate reduced rates of SSBR, not DSBR, as the source of both neurodevelopmental and neurodegenerative pathology in PNKP-mutated disease, and the extent and nature of this reduction as the primary determinant of disease severity.
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Affiliation(s)
- Ilona Kalasova
- Department of Genome Dynamics, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague 4, 142 20, Czech Republic
| | - Richard Hailstone
- Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton BN1 9RQ, UK
| | - Janin Bublitz
- Department of Human Genetics, Hannover Medical School, Hannover, Germany
| | - Jovel Bogantes
- Servicio de Cirugía Reconstructiva, Hospital Rafael Ángel Calderón Guardia, Caja Costarricense de Seguro Social, San José, Costa Rica
| | - Winfried Hofmann
- Department of Human Genetics, Hannover Medical School, Hannover, Germany
| | - Alejandro Leal
- Section of Genetics and Biotechnology, School of Biology, University of Costa Rica, San José, Costa Rica
| | - Hana Hanzlikova
- Department of Genome Dynamics, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague 4, 142 20, Czech Republic.,Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton BN1 9RQ, UK
| | - Keith W Caldecott
- Department of Genome Dynamics, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague 4, 142 20, Czech Republic.,Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton BN1 9RQ, UK
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10
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Yang B, Zhang B, Cao Z, Xu X, Huo Z, Zhang P, Xiang S, Zhao Z, Lv C, Meng M, Zhang G, Dong L, Shi S, Yang L, Zhou Q. The lipogenic LXR-SREBF1 signaling pathway controls cancer cell DNA repair and apoptosis and is a vulnerable point of malignant tumors for cancer therapy. Cell Death Differ 2020; 27:2433-2450. [PMID: 32144382 PMCID: PMC7370224 DOI: 10.1038/s41418-020-0514-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 01/23/2020] [Accepted: 02/03/2020] [Indexed: 01/13/2023] Open
Abstract
Cancer cells are defective in DNA repair, so they experience increased DNA strand breaks, genome instability, gene mutagenesis, and tumorigenicity; however, multiple classic DNA repair genes and pathways are strongly activated in malignant tumor cells to compensate for the DNA repair deficiency and gain an apoptosis resistance. The mechanisms underlying this phenomenon in cancer are unclear. We speculate that a key DNA repair gene or signaling pathway in cancer has not yet been recognized. Here, we show that the lipogenic liver X receptor (LXR)-sterol response element binding factor-1 (SREBF1) axis controls the transcription of a key DNA repair gene polynucleotide kinase/phosphatase (PNKP), thereby governing cancer cell DNA repair and apoptosis. Notably, the PNKP levels were significantly reduced in 95% of human pancreatic cancer (PC) patients, particularly deep reduction for sixfold in all of the advanced-stage PC cases. PNKP is also deficient in three other types of cancer that we examined. In addition, the expression of LXRs and SREBF1 was significantly reduced in the tumor tissues from human PC patients compared with the adjacent normal tissues. The newly identified LXR-SREBF1-PNKP signaling pathway is deficient in PC, and the defect in the pathway contributes to the DNA repair deficiency in the cancer. Strikingly, further diminution of the vulnerable LXR-SREBF1-PNKP signaling pathway using a small molecule triptonide, a new LXR antagonist identified in this investigation, at a concentration of 8 nM robustly activated tumor-suppressor p53 and readily elevated cancer cell DNA strand breaks over an apoptotic threshold, and selectively induced PC cell apoptosis, resulting in almost complete elimination of tumors in xenograft mice without obvious complications. Our findings provide new insight into DNA repair and apoptosis in cancer, and offer a new platform for developing novel anticancer therapeutics.
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Affiliation(s)
- Bo Yang
- Department of General Surgery, The Third Affiliated Hospital of Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- The First People's Hospital of Changzhou, Changzhou, 213003, P. R. China
| | - Bin Zhang
- Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- State Key Laboratory of Radiation Medicine, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- 2011 Collaborative Innovation Center of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- Center of Systems Medicine, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100005, China
- Suzhou Institute of Systems Medicine, Suzhou, 215123, China
| | - Zhifei Cao
- Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China.
- State Key Laboratory of Radiation Medicine, Soochow University, Suzhou, Jiangsu, 215123, P. R. China.
- Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, Soochow University, Suzhou, Jiangsu, 215123, P. R. China.
- 2011 Collaborative Innovation Center of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China.
- Department of Pathology, The Second Affiliated Hospital of Soochow University, Suzhou, Jiangsu, 215123, P. R. China.
| | - Xingdong Xu
- Department of General Surgery, The People's Hospital of China, Three Gorges University, Yichang, 443000, P. R. China
- The First People's Hospital of Yichang, Yichang, 443000, P. R. China
| | - Zihe Huo
- Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- State Key Laboratory of Radiation Medicine, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- 2011 Collaborative Innovation Center of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Pan Zhang
- Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- State Key Laboratory of Radiation Medicine, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- 2011 Collaborative Innovation Center of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Shufen Xiang
- Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- State Key Laboratory of Radiation Medicine, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- 2011 Collaborative Innovation Center of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Zhe Zhao
- Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- State Key Laboratory of Radiation Medicine, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- 2011 Collaborative Innovation Center of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Chunping Lv
- Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- State Key Laboratory of Radiation Medicine, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- 2011 Collaborative Innovation Center of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Mei Meng
- Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- State Key Laboratory of Radiation Medicine, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- 2011 Collaborative Innovation Center of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Gaochuan Zhang
- Department of Bioinformatics, College of Basic Medical Science, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Liang Dong
- Department of Pathology, College of Basic Medical Science, Soochow University, Suzhou, Jiangsu, 215123, P. R. China
| | - Shucheng Shi
- Department of General Surgery, The Third Affiliated Hospital of Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- The First People's Hospital of Changzhou, Changzhou, 213003, P. R. China
| | - Lan Yang
- Department of General Surgery, The Third Affiliated Hospital of Soochow University, Suzhou, Jiangsu, 215123, P. R. China
- The First People's Hospital of Changzhou, Changzhou, 213003, P. R. China
| | - Quansheng Zhou
- Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China.
- State Key Laboratory of Radiation Medicine, Soochow University, Suzhou, Jiangsu, 215123, P. R. China.
- Key Laboratory of Thrombosis and Hemostasis, Ministry of Health, Soochow University, Suzhou, Jiangsu, 215123, P. R. China.
- 2011 Collaborative Innovation Center of Hematology, Soochow University, Suzhou, Jiangsu, 215123, P. R. China.
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Deficiency in classical nonhomologous end-joining-mediated repair of transcribed genes is linked to SCA3 pathogenesis. Proc Natl Acad Sci U S A 2020; 117:8154-8165. [PMID: 32205441 DOI: 10.1073/pnas.1917280117] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Spinocerebellar ataxia type 3 (SCA3) is a dominantly inherited neurodegenerative disease caused by CAG (encoding glutamine) repeat expansion in the Ataxin-3 (ATXN3) gene. We have shown previously that ATXN3-depleted or pathogenic ATXN3-expressing cells abrogate polynucleotide kinase 3'-phosphatase (PNKP) activity. Here, we report that ATXN3 associates with RNA polymerase II (RNAP II) and the classical nonhomologous end-joining (C-NHEJ) proteins, including PNKP, along with nascent RNAs under physiological conditions. Notably, ATXN3 depletion significantly decreased global transcription, repair of transcribed genes, and error-free double-strand break repair of a 3'-phosphate-containing terminally gapped, linearized reporter plasmid. The missing sequence at the terminal break site was restored in the recircularized plasmid in control cells by using the endogenous homologous transcript as a template, indicating ATXN3's role in PNKP-mediated error-free C-NHEJ. Furthermore, brain extracts from SCA3 patients and mice show significantly lower PNKP activity, elevated p53BP1 level, more abundant strand-breaks in the transcribed genes, and degradation of RNAP II relative to controls. A similar RNAP II degradation is also evident in mutant ATXN3-expressing Drosophila larval brains and eyes. Importantly, SCA3 phenotype in Drosophila was completely amenable to PNKP complementation. Hence, salvaging PNKP's activity can be a promising therapeutic strategy for SCA3.
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