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Cuarenta A, Kigar SL, Keese AP, Guagliardo SE, Chang L, Bakshi VP, Auger AP. DNA topoisomerase Top3β is impacted by early life stress in the developing female and male rat brain. Brain Res 2023; 1809:148339. [PMID: 36966960 DOI: 10.1016/j.brainres.2023.148339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 03/20/2023] [Accepted: 03/21/2023] [Indexed: 04/17/2023]
Abstract
DNA topoisomerases are essential for preserving genomic integrity. DNA topoisomerases induce breakage of DNA to facilitate replication and transcription by relaxing DNA and relieving supercoiling. Aberrant expression and deletions of topoisomerases are associated with psychiatric disorders such as schizophrenia and autism. Our study investigated the effects of early life stress (ELS) on three topoisomerases, Top1, Top3α, and Top3β in the developing rat brain. Newborn rats were exposed to a predator odor stress on postnatal days 1, 2, and 3; brain tissue was collected either 30 min after the last stressor on postnatal day 3 or during the juvenile period. We found that exposure to predator odor resulted in a decrease in Top3β expression levels in the neonatal male amygdala and in the juvenile prefrontal cortex of males and females. These data suggest that developing males and females respond differently to predator odor-induced stress. As ELS results in lower Top3β levels, these data suggest that ELS experienced during development may have consequences for genomic structural integrity and increased mental health risk.
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Affiliation(s)
- Amelia Cuarenta
- Department of Psychology, University of Wisconsin-Madison, United States.
| | - Stacey L Kigar
- Molecular and Cellular Pharmacology Training Program, University of Wisconsin-Madison, United States
| | - Ashley P Keese
- Department of Psychology, University of Wisconsin-Madison, United States
| | - Sarah E Guagliardo
- Department of Psychology, University of Wisconsin-Madison, United States
| | - Liza Chang
- Department of Psychology, University of Wisconsin-Madison, United States
| | - Vaishali P Bakshi
- Department of Psychiatry, University of Wisconsin-Madison, United States; Neuroscience Training Program, University of Wisconsin-Madison, United States
| | - Anthony P Auger
- Department of Psychology, University of Wisconsin-Madison, United States; Neuroscience Training Program, University of Wisconsin-Madison, United States.
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2
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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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Affiliation(s)
| | - Ram Madabhushi
- Departments of Psychiatry, Neuroscience, and Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, United States
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3
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Gokoolparsadh A, Fang Z, Braidy N, Voineagu I. Topoisomerase I inhibition leads to length-dependent gene expression changes in human primary astrocytes. GENOMICS DATA 2017; 11:113-115. [PMID: 28119819 PMCID: PMC5238604 DOI: 10.1016/j.gdata.2016.12.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 11/29/2016] [Accepted: 12/07/2016] [Indexed: 11/18/2022]
Abstract
Topoisomerase I is required for the proper expression of long genes (> 100 kb) in mouse and human cortical neurons, including many candidate genes for autism spectrum disorder (ASD) [1]. Given the important role of astrocytes in brain development [2], we investigated whether long genes, including autism susceptibility genes, also require topoisomerase I expression in human primary astrocytes. We carried genome-wide expression profiling of cultured human primary astrocytes following treatment with the topoisomerase I inhibitor Topotecan, using Illumina microarrays. We identified several thousands of differentially expressed genes and confirmed that topoisomerase I inhibition affects gene expression in human primary astrocytes in a length-dependent manner. We also identified over 20 ASD-associated genes that show topoisomerase-dependent gene expression in human primary astrocytes but have not been previously reported as topoisomerase-I-dependent in neurons. The microarray data have been deposited in NCBI GEO (https://www.ncbi.nlm.nih.gov/geo/) under accession number GSE90052. Topoisomerase I inhibition leads to length-dependent gene expression changes in human primary astrocytes. Long genes are found to be down-regulated in astrocytes, consistent with previous evidence from cortical neurons. Over 20 ASD-associated genes show topoisomerase-dependent expression in astrocytes.
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Affiliation(s)
- Akira Gokoolparsadh
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
| | - Zhiming Fang
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
| | - Nady Braidy
- Centre for Healthy Brain Ageing, School of Psychiatry, University of New South Wales, Sydney, Australia
| | - Irina Voineagu
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
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4
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Rossi SL, Lumpkin CJ, Harris AW, Holbrook J, Gentillon C, McCahan SM, Wang W, Butchbach MER. Identification of early gene expression changes in primary cultured neurons treated with topoisomerase I poisons. Biochem Biophys Res Commun 2016; 479:319-324. [PMID: 27641670 DOI: 10.1016/j.bbrc.2016.09.068] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 09/14/2016] [Indexed: 10/21/2022]
Abstract
Topoisomerase 1 (TOP1) poisons like camptothecin (CPT) are currently used in cancer chemotherapy but these compounds can have damaging, off-target effects on neurons leading to cognitive, sensory and motor deficits. To understand the molecular basis for the enhanced sensitivity of neurons to CPT, we examined the effects of compounds that inhibit TOP1-CPT, actinomycin D (ActD) and β-lapachone (β-Lap)-on primary cultured rat motor (MN) and cortical (CN) neurons as well as fibroblasts. Neuronal cells expressed higher levels of Top1 mRNA than fibroblasts but transcript levels are reduced in all cell types after treatment with CPT. Microarray analysis was performed to identify differentially regulated transcripts in MNs in response to a brief exposure to CPT. Pathway analysis of the differentially expressed transcripts revealed activation of ERK and JNK signaling cascades in CPT-treated MNs. Immediate-early genes like Fos, Egr-1 and Gadd45b were upregulated in CPT-treated MNs. Fos mRNA levels were elevated in all cell types treated with CPT; Egr-1, Gadd45b and Dyrk3 transcript levels, however, increased in CPT-treated MNs and CNs but decreased in CPT-treated fibroblasts. These transcripts may represent new targets for the development of therapeutic agents that mitigate the off-target effects of chemotherapy on the nervous system.
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Affiliation(s)
- Sharyn L Rossi
- Center for Applied Clinical Genomics, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for Children, Wilmington, DE, USA
| | - Casey J Lumpkin
- Center for Applied Clinical Genomics, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for Children, Wilmington, DE, USA; Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - Ashlee W Harris
- Center for Applied Clinical Genomics, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for Children, Wilmington, DE, USA
| | - Jennifer Holbrook
- Biomolecular Core Laboratory, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for Children, Wilmington, DE, USA
| | - Cinsley Gentillon
- Center for Applied Clinical Genomics, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for Children, Wilmington, DE, USA; Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - Suzanne M McCahan
- Center for Pediatric Research, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for Children, Wilmington, DE, USA; Bioinformatics Core Facility, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for Children, Wilmington, DE, USA; Department of Pediatrics, Thomas Jefferson University, Philadelphia, PA, USA
| | - Wenlan Wang
- Center for Applied Clinical Genomics, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for Children, Wilmington, DE, USA; Center for Pediatric Research, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for Children, Wilmington, DE, USA
| | - Matthew E R Butchbach
- Center for Applied Clinical Genomics, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for Children, Wilmington, DE, USA; Center for Pediatric Research, Nemours Biomedical Research, Nemours Alfred I. duPont Hospital for Children, Wilmington, DE, USA; Department of Biological Sciences, University of Delaware, Newark, DE, USA; Department of Pediatrics, Thomas Jefferson University, Philadelphia, PA, USA.
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5
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Abstract
Topoisomerases are unique enzymes that regulate torsional stress in DNA to enable essential genome functions, including DNA replication and transcription. Although all cells in an organism require topoisomerases to maintain normal function, the nervous system in particular shows a vital need for these enzymes. Indeed, a range of inherited human neurologic syndromes, including neurodegeneration, schizophrenia and intellectual impairment, are associated with aberrant topoisomerase function. Much remains unknown regarding the tissue-specific function of neural topoisomerases or the connections between these enzymes and disease aetiology. Precisely how topoisomerases regulate genome dynamics within the nervous system is therefore a crucial research question.
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6
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Harkin LF, Gerrelli D, Gold Diaz DC, Santos C, Alzu'bi A, Austin CA, Clowry GJ. Distinct expression patterns for type II topoisomerases IIA and IIB in the early foetal human telencephalon. J Anat 2015; 228:452-63. [PMID: 26612825 PMCID: PMC4832326 DOI: 10.1111/joa.12416] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/15/2015] [Indexed: 01/16/2023] Open
Abstract
TOP2A and TOP2B are type II topoisomerase enzymes that have important but distinct roles in DNA replication and RNA transcription. Recently, TOP2B has been implicated in the transcription of long genes in particular that play crucial roles in neural development and are susceptible to mutations contributing to neurodevelopmental conditions such as autism and schizophrenia. This study maps their expression in the early foetal human telencephalon between 9 and 12 post‐conceptional weeks. TOP2A immunoreactivity was restricted to cell nuclei of the proliferative layers of the cortex and ganglionic eminences (GE), including the ventricular zone and subventricular zone (SVZ) closely matching expression of the proliferation marker KI67. Comparison with sections immunolabelled for NKX2.1, a medial GE (MGE) marker, and PAX6, a cortical progenitor cell and lateral GE (LGE) marker, revealed that TOP2A‐expressing cells were more abundant in MGE than the LGE. In the cortex, TOP2B is expressed in cell nuclei in both proliferative (SVZ) and post‐mitotic compartments (intermediate zone and cortical plate) as revealed by comparison with immunostaining for PAX6 and the post‐mitotic neuron marker TBR1. However, co‐expression with KI67 was rare. In the GE, TOP2B was also expressed by proliferative and post‐mitotic compartments. In situ hybridisation studies confirmed these patterns of expression, except that TOP2A mRNA is restricted to cells in the G2/M phase of division. Thus, during early development, TOP2A is likely to have a role in cell proliferation, whereas TOP2B is expressed in post‐mitotic cells and may be important in controlling expression of long genes even at this early stage.
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Affiliation(s)
- Lauren F Harkin
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK.,Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | | | | | - Chloe Santos
- HDBR Resource, UCL Institute of Child Health, London, UK
| | - Ayman Alzu'bi
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK.,Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, UK
| | - Caroline A Austin
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
| | - Gavin J Clowry
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK
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7
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Topoisomerases interlink genetic network underlying autism. Int J Dev Neurosci 2015; 47:361-8. [PMID: 26456455 DOI: 10.1016/j.ijdevneu.2015.07.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 05/20/2015] [Accepted: 07/12/2015] [Indexed: 12/31/2022] Open
Abstract
DNA topoisomerases belong to the group of proteins that play an important role in the organizational dynamics of the human genome. Their enzymatic activity solves topological strain rising from DNA supercoiling occurring during transcription. DNA topoisomerases are especially important for transcription of genes involved in neurodevelopment. Disruption of topoisomerase activity in animal models resulted in impaired neurodevelopment and changed brain architecture. Recent research revealed that topoisomerases induced expression of the same group of genes as those associated with autism. Transcriptional inhibition of neuronal genes during critical stages of brain development may be responsible for pathology of neurodevelopmental disorders such as autism. In this review we aim to outline the role of topoisomerase in neurodevelopment and its possible linkage to neuropathology of autism.
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Abstract
Topotecan is a topoisomerase 1 (TOP1) inhibitor that is used to treat various forms of cancer. We recently found that topotecan reduces the expression of multiple long genes, including many neuronal genes linked to synapses and autism. However, whether topotecan alters synaptic protein levels and synapse function is currently unknown. Here we report that in primary cortical neurons, topotecan depleted synaptic proteins that are encoded by extremely long genes, including Neurexin-1, Neuroligin-1, Cntnap2, and GABA(A)β3. Topotecan also suppressed spontaneous network activity without affecting resting membrane potential, action potential threshold, or neuron health. Topotecan strongly suppressed inhibitory neurotransmission via pre- and postsynaptic mechanisms and reduced excitatory neurotransmission. The effects on synaptic protein levels and inhibitory neurotransmission were fully reversible upon drug washout. Collectively, our findings suggest that TOP1 controls the levels of multiple synaptic proteins and is required for normal excitatory and inhibitory synaptic transmission.
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King IF, Yandava CN, Mabb AM, Hsiao JS, Huang HS, Pearson BL, Calabrese JM, Starmer J, Parker JS, Magnuson T, Chamberlain SJ, Philpot BD, Zylka MJ. Topoisomerases facilitate transcription of long genes linked to autism. Nature 2013; 501:58-62. [PMID: 23995680 PMCID: PMC3767287 DOI: 10.1038/nature12504] [Citation(s) in RCA: 304] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 07/24/2013] [Indexed: 12/12/2022]
Abstract
Topoisomerases are expressed throughout the developing and adult brain and are mutated in some individuals with autism spectrum disorder (ASD). However, how topoisomerases are mechanistically connected to ASD is unknown. Here we found that topotecan, a Topoisomerase 1 (TOP1) inhibitor, dose-dependently reduced the expression of extremely long genes in mouse and human neurons, including nearly all genes >200 kb. Expression of long genes was also reduced following knockdown of Top1 or Top2b in neurons, highlighting that each enzyme was required for full expression of long genes. By mapping RNA polymerase II density genome-wide in neurons, we found that this length-dependent effect on gene expression was due to impaired transcription elongation. Interestingly, many high confidence ASD candidate genes are exceptionally long and were reduced in expression following TOP1 inhibition. Our findings suggest that chemicals and genetic mutations that impair topoisomerases could commonly contribute to ASD and other neurodevelopmental disorders.
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Affiliation(s)
- Ian F King
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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10
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Levi I, Segev Y, Priel E. Type 1 diabetes affects topoisomerase I activity and GlcNAcylation in rat organs: Kidney, liver and pancreas. Glycobiology 2012; 22:704-13. [DOI: 10.1093/glycob/cws008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Topoisomerase inhibitors unsilence the dormant allele of Ube3a in neurons. Nature 2011; 481:185-9. [PMID: 22190039 PMCID: PMC3257422 DOI: 10.1038/nature10726] [Citation(s) in RCA: 261] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 11/22/2011] [Indexed: 01/07/2023]
Abstract
Angelman syndrome is a severe neurodevelopmental disorder caused by deletion or mutation of the maternal allele of the ubiquitin protein ligase E3A (Ube3a)1–3. In neurons, the paternal allele of Ube3a is intact but epigenetically silenced4–6, raising the possibility that Angelman syndrome could be treated by activating this silenced allele to restore functional UBE3A protein7,8. Using an unbiased, high-content screen in primary cortical neurons from mice, we identified twelve topoisomerase I inhibitors and four topoisomerase II inhibitors that unsilence the paternal Ube3a allele. These drugs included topotecan, irinotecan, etoposide, and dexrazoxane (ICRF-187). At nanomolar concentrations, topotecan upregulated catalytically active UBE3A in neurons from maternal Ube3a-null mice. Topotecan concomitantly downregulated expression of the Ube3a antisense transcript that overlaps the paternal copy of Ube3a9–11. These results suggest that topotecan unsilences Ube3a in cis by reducing transcription of an imprinted antisense RNA. When administered in vivo, topotecan unsilenced the paternal Ube3a allele in several regions of the nervous system, including neurons in the hippocampus, neocortex, striatum, cerebellum and spinal cord. Paternal expression of Ube3a remained elevated in a subset of spinal cord neurons for at least twelve weeks after cessation of topotecan treatment, suggesting transient topoisomerase inhibition can have enduring effects on gene expression. While potential off-target effects remain to be investigated, our findings suggest a therapeutic strategy for reactivating the functional but dormant allele of Ube3a in patients with Angelman syndrome.
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Kerzendorfer C, Hart L, Colnaghi R, Carpenter G, Alcantara D, Outwin E, Carr AM, O’Driscoll M. CUL4B-deficiency in humans: Understanding the clinical consequences of impaired Cullin 4-RING E3 ubiquitin ligase function. Mech Ageing Dev 2011; 132:366-73. [DOI: 10.1016/j.mad.2011.02.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 01/18/2011] [Accepted: 02/08/2011] [Indexed: 01/21/2023]
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13
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Kerzendorfer C, Whibley A, Carpenter G, Outwin E, Chiang SC, Turner G, Schwartz C, El-Khamisy S, Raymond FL, O'Driscoll M. Mutations in Cullin 4B result in a human syndrome associated with increased camptothecin-induced topoisomerase I-dependent DNA breaks. Hum Mol Genet 2010; 19:1324-34. [PMID: 20064923 DOI: 10.1093/hmg/ddq008] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
CUL4A and B encode subunits of E3-ubiquitin ligases implicated in diverse processes including nucleotide excision repair, regulating gene expression and controlling DNA replication fork licensing. But, the functional distinction between CUL4A and CUL4B, if any, is unclear. Recently, mutations in CUL4B were identified in humans associated with mental retardation, relative macrocephaly, tremor and a peripheral neuropathy. Cells from these patients offer a unique system to help define at the molecular level the consequences of defective CUL4B specifically. We show that these patient-derived cells exhibit sensitivity to camptothecin (CPT), impaired CPT-induced topoisomerase I (Topo I) degradation and ubiquitination, thereby suggesting Topo I to be a novel Cul4-dependent substrate. Consistent with this, we also find that these cells exhibit increased levels of CPT-induced DNA breaks. Furthermore, over-expression of known CUL4-dependent substrates including Cdt1 and p21 appear to be a feature of these patient-derived cells. Collectively, our findings highlight the interplay between CUL4A and CUL4B and provide insight into the pathogenesis of CUL4B-deficiency in humans.
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Zehorai E, Eitan E, Hershfinkel M, Sekler I, Priel E. Glutamate regulates the activity of topoisomerase I in mouse cerebellum. Mol Neurobiol 2008; 38:242-52. [PMID: 18982460 DOI: 10.1007/s12035-008-8044-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Accepted: 10/10/2008] [Indexed: 10/21/2022]
Abstract
Topoisomerase I (topo I) is a nuclear enzyme which participates in most DNA transactions. It was shown to be inhibited in depolarized neurons by poly adenosine diphosphate (ADP)-ribosylation of the enzyme protein. We demonstrated previously an age and sex dependent topo I activity and enzyme protein level in the various regions of mouse brain. A specific distribution pattern of topo I was observed and the inhibitory neurons exhibited the highest enzyme activity and protein level in both the nucleus and the cytoplasm. Here, we show that neurotransmitters (glutamate and gamma-aminobutyric acid (GABA)) regulate the activity of topo I in mouse cerebellum sections. Glutamate exhibited a significant time-dependent inhibition of topo I activity but no effect of the enzyme protein level. GABA in contrary only slightly and transiently inhibited topo I activity. The inhibitory effect of glutamate was mediated by Ca(+2) and by ADP-ribosylation of topo I protein and the glutamate ionotropic receptors were involved. Glutamate also diminished the inhibitory effect of topotecan on topo I. These results point to distinct and highly specific effects of the major neurotransmitters on topo I activity in the cerebellum suggesting that topo I possesses a specific role in the brain which differs from its known biological functions.
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Affiliation(s)
- Eldar Zehorai
- The Shraga Segal Department of Microbiology & Immunology, Ben-Gurion University Cancer Research Center, Faculty of Health Sciences, Ben-Gurion University, Beer-Sheva, 84105, Israel
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15
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Reuveni D, Halperin D, Shalit I, Priel E, Fabian I. Quinolones as enhancers of camptothecin-induced cytotoxic and anti-topoisomerase I effects. Biochem Pharmacol 2008; 75:1272-81. [DOI: 10.1016/j.bcp.2007.11.014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Revised: 11/11/2007] [Accepted: 11/28/2007] [Indexed: 02/02/2023]
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16
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Gorodetsky E, Calkins S, Ahn J, Brooks P. ATM, the Mre11/Rad50/Nbs1 complex, and topoisomerase I are concentrated in the nucleus of Purkinje neurons in the juvenile human brain. DNA Repair (Amst) 2007; 6:1698-707. [PMID: 17706468 PMCID: PMC2797317 DOI: 10.1016/j.dnarep.2007.06.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Revised: 06/11/2007] [Accepted: 06/13/2007] [Indexed: 11/17/2022]
Abstract
The genetic disease ataxia telangiectasia (AT) results from mutations in the ataxia telangiectasia mutated (ATM) gene. AT patients develop a progressive degeneration of cerebellar Purkinje neurons. Surprisingly, while ATM plays a criticial role in the cellular reponse to DNA damage, previous studies have localized ATM to the cytoplasm of rodent and human Purkinje neurons. Here we show that ATM is primarily localized to the nucleus in cerebellar Purkinje neurons in postmortem human brain tissue samples, although some light cytoplasmic ATM staining was also observed. No ATM staining was observed in brain tissue samples from AT patients, verifying the specificity of the antibody. We also found that antibodies against components of the Mre11/Rad50/Nbs1 (MRN) complex showed strong staining in Purkinje cell nuclei. However, while ATM is present in both the nucleoplasm and nucleolus, MRN proteins are excluded from the nucleolus. We also observed very high levels of topoisomerase 1 (TOP1) in the nucleus, and specifically the nucleolus, of human Purkinje neurons. Our results have direct implications for understanding the mechanisms of neurodegeneration in AT and AT-like disorder.
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Affiliation(s)
- Elena Gorodetsky
- Section on Molecular Neurobiology, Laboratory of Neurogenetics, National Institute on Alcohol Abuse and Alcoholism, 5625 Fishers Lane, Room 3S-32, MSC 9412, Bethesda, MD 20952-9412, USA, 301-496-7920, 301-480-2839 (FAX),
| | - Sarah Calkins
- Section on Molecular Neurobiology, Laboratory of Neurogenetics, National Institute on Alcohol Abuse and Alcoholism, 5625 Fishers Lane, Room 3S-32, MSC 9412, Bethesda, MD 20952-9412, USA, 301-496-7920, 301-480-2839 (FAX),
| | - Julia Ahn
- Section on Molecular Neurobiology, Laboratory of Neurogenetics, National Institute on Alcohol Abuse and Alcoholism, 5625 Fishers Lane, Room 3S-32, MSC 9412, Bethesda, MD 20952-9412, USA, 301-496-7920, 301-480-2839 (FAX),
| | - P.J. Brooks
- Section on Molecular Neurobiology, Laboratory of Neurogenetics, National Institute on Alcohol Abuse and Alcoholism, 5625 Fishers Lane, Room 3S-32, MSC 9412, Bethesda, MD 20952-9412, USA, 301-496-7920, 301-480-2839 (FAX),
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17
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Har-Vardi I, Mali R, Breietman M, Sonin Y, Albotiano S, Levitas E, Potashnik G, Priel E. DNA topoisomerases I and II in human mature sperm cells: characterization and unique properties. Hum Reprod 2007; 22:2183-9. [PMID: 17656417 DOI: 10.1093/humrep/dem170] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The condensed state of the human sperm's chromatin is essential for the compact structure of the spermatozoon head, which is important for the fertilization process. The enzymes DNA topoisomerases (topo I and topo II) are responsible for the topological structure of the chromatin in somatic cells. The activities and the characterization of topoisomerases in mature human sperm cells have not been previously investigated. METHODS Sperm cells were purified from the semen of healthy donors by standard procedures and assays measuring the activities, protein size and sensitivity to inhibitors of topoisomerases were performed. RESULTS Topo I and topo II DNA relaxation activities are present in nuclear extracts derived from human sperm. The sperm topo I activity is inhibited by camptothecin, similarly to the somatic enzyme. An 85 kDa sperm protein, compared with the 100 kDa somatic topo IB enzyme, reacted with anti-human topo I antibody. Sperm topo II lacks the DNA decatenation activity of the somatic enzyme and a 97 kDa protein, compared with the 170 kDa somatic topo IIalpha enzyme, was detected with anti-human topo II antibody. Sperm nuclear extracts contained inhibitors of somatic topo II decatenation activity. CONCLUSIONS Topoisomerase I and II activities as well as topo I and topo II proteins are present in mature human sperm cells. These enzymes possess unique properties compared with their somatic counterparts.
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Affiliation(s)
- I Har-Vardi
- IVF unit, Department of Obstetrics and Gynaecology, Soroka University Medical Center, Faculty of Health Sciences, Ben-Gurion University, Beer-Sheva 84105, Israel
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18
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Abstract
DNA topoisomerase I is an essential nuclear enzyme involved in resolving the torsional stress associated with DNA replication, transcription, and chromatin condensation. Here we report the discovery of a seizure-suppressor mutant, top1(JS), which suppresses seizures in a Drosophila model of human epilepsy. A P-element mutagenesis screen using easily shocked seizure-sensitive mutant as a genetic background identified top1(JS), which plays a novel role in regulating nervous system excitability. Plasmid rescue, excision, complementation, and sequencing analyses verified that top1(JS) results from a P-element insertion in the 5' untranslated region. Quantitative reverse transcription analysis on wild-type and mutant fly heads showed that the top1(JS) mutation causes reduced transcription level in the CNS, suggesting a partial loss-of-function mutation. Electrophysiological experiments revealed normal seizure thresholds in top1(JS) mutants, which are different from other seizure suppressors identified previously, suggesting a novel mechanism underlying seizure suppression by top1(JS). The pharmacological camptothecin feeding experiment and cell death analysis suggested that the seizure suppression by top1(JS) may occur via increased neuronal apoptosis. Furthermore, overexpression of the DIAP1 (Drosophila inhibitor of apoptosis 1) gene rescues top1(JS) suppression, providing additional support for a neural apoptosis suppression mechanism. The top1(JS) mutation is the first viable partial loss-of-function mutation identified in higher eukaryotes, and the results presented here point to a novel function for topo I in construction and/or maintenance of circuits required for seizure propagation in vivo.
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Affiliation(s)
- Juan Song
- Division of Insect Biology, Department of Environmental Science, Policy and Management, University of California, Berkeley, Berkeley, California 94720, USA.
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