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Lim SE, Vicente-Munuera P, Mao Y. Forced back into shape: Mechanics of epithelial wound repair. Curr Opin Cell Biol 2024; 87:102324. [PMID: 38290420 DOI: 10.1016/j.ceb.2024.102324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 12/20/2023] [Accepted: 01/03/2024] [Indexed: 02/01/2024]
Abstract
Wound repair, the closing of a hole, is inherently a physical process that requires the change of shape of materials, in this case, cells and tissues. Not only is efficient and accurate wound repair critical for restoring barrier function and reducing infection, but it is also critical for restoring the complex three-dimensional architecture of an organ. This re-sculpting of tissues requires the complex coordination of cell behaviours in multiple dimensions, in space and time, to ensure that the repaired structure can continue functioning optimally. Recent evidence highlights the importance of cell and tissue mechanics in 2D and 3D to achieve such seamless wound repair.
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Affiliation(s)
- Shu En Lim
- Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK; Institute for the Physics of Living Systems, University College London, Gower Street, London WC1E 6BT, UK
| | - Pablo Vicente-Munuera
- Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK; Institute for the Physics of Living Systems, University College London, Gower Street, London WC1E 6BT, UK
| | - Yanlan Mao
- Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK; Institute for the Physics of Living Systems, University College London, Gower Street, London WC1E 6BT, UK.
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2
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Lim SE, Joseph MD, de Winde CM, Acton SE, Simoncelli S. Quantitative single molecule analysis of podoplanin clustering in fibroblastic reticular cells uncovers CD44 function. Open Biol 2023; 13:220377. [PMID: 37161290 PMCID: PMC10170195 DOI: 10.1098/rsob.220377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 04/06/2023] [Indexed: 05/11/2023] Open
Abstract
Upon initial immune challenge, dendritic cells (DCs) migrate to lymph nodes and interact with fibroblastic reticular cells (FRCs) via C-type lectin-like receptor 2 (CLEC-2). CLEC-2 binds to the membrane glycoprotein podoplanin (PDPN) on FRCs, inhibiting actomyosin contractility through the FRC network and permitting lymph node expansion. The hyaluronic acid receptor CD44 is known to be required for FRCs to respond to DCs but the mechanism of action is not fully elucidated. Here, we use DNA-PAINT, a quantitative single molecule super-resolution technique, to visualize and quantify how PDPN clustering is regulated in the plasma membrane of FRCs. Our results indicate that CLEC-2 interaction leads to the formation of large PDPN clusters (i.e. more than 12 proteins per cluster) in a CD44-dependent manner. These results suggest that CD44 expression is required to stabilize large pools of PDPN at the membrane of FRCs upon CLEC-2 interaction, revealing the molecular mechanism through which CD44 facilitates cellular crosstalk between FRCs and DCs.
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Affiliation(s)
- Shu En Lim
- Stromal Immunology Group, MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
- London Centre for Nanotechnology, University College London, London WC1H 0AH, UK
| | - Megan D. Joseph
- London Centre for Nanotechnology, University College London, London WC1H 0AH, UK
- Department of Chemistry, University College London, London WC1H 0AJ, UK
| | - Charlotte M. de Winde
- Stromal Immunology Group, MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
- Department of Molecular Cell Biology & Immunology, Amsterdam UMC location Vrije Universiteit Amsterdam, De Boelelaan 1117, Amsterdam, The Netherlands
- Cancer Center Amsterdam, Cancer Biology & Immunology, Amsterdam, The Netherlands
- Amsterdam Institute for Infection & Immunity, Cancer Immunology, Amsterdam, The Netherlands
| | - Sophie E. Acton
- Stromal Immunology Group, MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Sabrina Simoncelli
- London Centre for Nanotechnology, University College London, London WC1H 0AH, UK
- Department of Chemistry, University College London, London WC1H 0AJ, UK
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Lucke JA, Mooijaart SP, Heeren P, Singler K, McNamara R, Gilbert T, Nickel CH, Castejon S, Mitchell A, Mezera V, Van der Linden L, Lim SE, Thaur A, Karamercan MA, Blomaard LC, Dundar ZD, Chueng KY, Islam F, de Groot B, Conroy S. Providing care for older adults in the Emergency Department: expert clinical recommendations from the European Task Force on Geriatric Emergency Medicine. Eur Geriatr Med 2021; 13:309-317. [PMID: 34738224 PMCID: PMC8568564 DOI: 10.1007/s41999-021-00578-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2021] [Accepted: 10/20/2021] [Indexed: 01/08/2023]
Abstract
Aim The aim was to develop expert clinical recommendations on Geriatric Emergency Medicine to be disseminated across Europe. Findings Eight posters with expert clinical guidelines on the most important topics in Geriatric Emergency Medicine are now available through https://posters.geriemeurope.eu/. Message Expert clinical recommendations for Geriatric Emergency Medicine in Europe were created and are ready for dissemination across Europe. Supplementary Information The online version contains supplementary material available at 10.1007/s41999-021-00578-1. Purpose Despite the rapidly expanding knowledge in the field of Geriatric Emergency Medicine in Europe, widespread implementation of change is still lacking. Many opportunities in everyday clinical care are missed to improve care for this susceptible and growing patient group. The aim was to develop expert clinical recommendations on Geriatric Emergency Medicine to be disseminated across Europe. Methods A group of multi-disciplinary experts in the field of Geriatric Emergency Medicine in Europe was assembled. Using a modified Delphi procedure, a prioritized list of topics related to Geriatric Emergency Medicine was created. Next, a multi-disciplinary group of nurses, geriatricians and emergency physicians performed a review of recent guidelines and literature to create recommendations. These recommendations were voted upon by a group of experts and placed on visually attractive posters. The expert group identified the following eight subject areas to develop expert recommendations on: Comprehensive Geriatric Assessment in the Emergency Department (ED), age/frailty adjusted risk stratification, delirium and cognitive impairment, medication reviews in the ED for older adults, family involvement, ED environment, silver trauma, end of life care in the acute setting. Results Eight posters with expert clinical recommendations on the most important topics in Geriatric Emergency Medicine are now available through https://posters.geriemeurope.eu/. Conclusion Expert clinical recommendations for Geriatric Emergency Medicine may help to improve care for older patients in the Emergency Department and are ready for dissemination across Europe. Supplementary Information The online version contains supplementary material available at 10.1007/s41999-021-00578-1.
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Affiliation(s)
- J A Lucke
- Department of Emergency Medicine, Spaarne Gasthuis, Haarlem, The Netherlands.
| | - S P Mooijaart
- Department of Internal Medicine, Section on Gerontology and Geriatrics, Leiden University Medical Center, Leiden, The Netherlands
| | - P Heeren
- Department of Public Health and Primary Care, Academic Centre for Nursing and Midwifery, KU Leuven, Leuven, Belgium.,Department of Geriatric Medicine, University Hospitals Leuven, Leuven, Belgium.,Research Foundation Flanders, Brussels, Belgium
| | - K Singler
- Department of Geriatrics, Klinikum Nürnberg, Paracelsus Private, Medical University, Nuremberg, Germany.,Institute for Biomedicine of Ageing, Friedrich-Alexander-University, Erlangen-Nuremberg, Erlangen, Germany
| | - R McNamara
- Department of Emergency Medicine, St. Vincent's University Hospital, Dublin, Ireland
| | - T Gilbert
- Department of Geriatric Medicine, Lyon-Sud University Hospital, Lyon, France
| | - C H Nickel
- Emergency Medicine, University Hospital Basel, Basel, Switzerland
| | - S Castejon
- Department of Geriatrics and Palliative Care, Consorci Sanitari de Terrassa, Terrassa, Barcelona, Spain
| | - A Mitchell
- Department of Emergency Medicine, Sligo University Hospital, Sligo, Ireland
| | - V Mezera
- Geriatric Center, Pardubice Hospital, Pardubice, Czech Republic
| | - L Van der Linden
- Pharmacy Department, University Hospitals Leuven, Leuven, Belgium.,Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium
| | - S E Lim
- Academic Geriatric Medicine, University of Southampton, Southampton, UK
| | - A Thaur
- Department of Emergency Medicine, Guy's and St.Thomas' NHS Foundation Trust, London, UK
| | - M A Karamercan
- Department of Emergency Medicine, Gazi University School of Medicine, Ankara, Turkey
| | - L C Blomaard
- Department of Internal Medicine, Section on Gerontology and Geriatrics, Leiden University Medical Center, Leiden, The Netherlands
| | - Z D Dundar
- Department of Emergency Medicine, Necmettin Erbakan University Meram Faculty of Medicine, Konya, Turkey
| | - K Y Chueng
- Accident and Emergency Department, United Christian Hospital, Kwun Tong, Hong Kong
| | - F Islam
- Department of Public Health and Primary Care, KU Leuven, Leuven, Belgium
| | - B de Groot
- Department of Emergency Medicine, Leiden University Medical Center, Leiden, The Netherlands
| | - S Conroy
- Geriatric Medicine, MRC Unit for Lifelong Health and Ageing at UCL, 5th Floor, 1-19 Torrington Place, London, WC1E 7HB, UK
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Tan QY, Ibrahim K, Cox NJ, Lim SE, Coutts L, Fraser S, Roberts HC. 39 The Experiences of Treatment Burden Among People with Parkinson’s Disease and Their Caregivers: A Systematic Review. Age Ageing 2021. [DOI: 10.1093/ageing/afab029.18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Introduction
Treatment burden is the “workload of healthcare and its impact on patient functioning and well-being”. High treatment burden may lead to non-adherence to treatment regimens, poor health outcomes, poor quality of life and wasted healthcare resources. Treatment burden among people with Parkinson’s (PwP) and their caregivers has not been previously explored.
Methods
Using five electronic databases (MEDLINE, Embase, CINAHL, Scopus and PsychInfo), we conducted a systematic review of studies published since 2006 when the first National Institute for Clinical Excellence (NICE) Clinical Guideline for Parkinson’s Disease was published. This allows an understanding of the impact of current healthcare systems on treatment burden. We included qualitative and mixed-method studies with a qualitative component that reported data from PwP and/or caregivers. Quantitative studies, qualitative data from clinical trials not related to usual care and grey literature were excluded. Two reviewers independently screened articles and extracted data. Data analysis was conducted using framework analysis.
Results
1757 articles were screened, and 39 included in this review. Understanding treatment burden among PwP and their caregivers was not the primary aim in any of the included studies. They described the experiences of those living at home and during hospital or care home admissions. Issues with medications (adherence to advice, effectiveness, side-effects and timing), obtaining appropriate levels of information and healthcare provision (lack of integrated care, care coordination and person-centred approach) were among factors that exacerbate treatment burden experienced by PwP and caregivers. Both reported the impact of Parkinson’s on their daily lives, physical and mental exhaustion of self-care and limitations on their role and social activities.
Conclusion
This review describes considerable treatment burden experienced by PwP and their caregivers and its major influences including aspects of current healthcare provision. Future research should focus on patient-centred care with service redesign to improve this treatment burden.
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Ngoi NYL, Heong V, Lee XW, Huang YQ, Thian YL, Choo BA, Lim D, Lim YW, Lim SE, Ilancheran A, Soong R, Tan DSP. Tumor molecular profiling of responders and non-responders following pembrolizumab monotherapy in chemotherapy resistant advanced cervical cancer. Gynecol Oncol Rep 2018; 24:1-5. [PMID: 29892689 PMCID: PMC5993533 DOI: 10.1016/j.gore.2018.01.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 01/24/2018] [Accepted: 01/28/2018] [Indexed: 12/18/2022] Open
Abstract
Optimal treatment for advanced cervical cancer after first line chemotherapy remains undefined. Immune checkpoint inhibition with pembrolizumab, a programmed cell death protein 1(PD-1) inhibitor, is under investigation. We analyzed the micro-environmental and molecular genetic profile of tumors from 4 patients with metastatic cervical cancer treated with off-label second-line pembrolizumab in an effort to identify predictive biomarkers. All patients received 2 mg/kg of pembrolizumab, 3-weekly until disease progression. Immunohistochemistry(IHC) for PD-1, PD-L1, CD3 and CD8, as well as next generation sequencing (NGS) for 50 cancer-related genes were performed on tumor samples. All patients tolerated treatment well with no discontinuation of treatment due to toxicity. One patient experienced dramatic and prolonged partial response, and remains stable on pembrolizumab with a progression free survival (PFS) of 21 months at the time of reporting of this series. Three patients experienced disease progression as best response. In the exceptional responder, there was no tumoral expression of PD-L1, however, combined positive score (CPS) for PD-L1 was 1 and we identified somatic mutations in ERBB4(R612W), PIK3CA(E542K) and RB1(E365K). In 2 patients, despite progressive disease defined by RECIST v1.1, symptom stabilization on pembrolizumab was observed. The tumors of both patients had PD-1 expression in ≥1% of stromal lymphocytes. All patients with response or clinical benefit had CPS for PD-L1 ≥ 1. NGS revealed PIK3CA mutations in 3 tumors. Pembrolizumab is a promising therapeutic option in advanced cervical cancer. Further evaluation of biomarkers may guide optimal patient selection.
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Affiliation(s)
- N Y L Ngoi
- Department of Hematology-Oncology, National University Cancer Institute, Singapore, 5 Lower Kent Ridge Rd, Singapore 119074, Republic of Singapore
| | - V Heong
- Department of Hematology-Oncology, National University Cancer Institute, Singapore, 5 Lower Kent Ridge Rd, Singapore 119074, Republic of Singapore.,Cancer Science Institute of Singapore, National University of Singapore, 14 Medical Drive, Singapore 117599, Republic of Singapore
| | - X W Lee
- Department of Hematology-Oncology, National University Cancer Institute, Singapore, 5 Lower Kent Ridge Rd, Singapore 119074, Republic of Singapore
| | - Y Q Huang
- Department of Hematology-Oncology, National University Cancer Institute, Singapore, 5 Lower Kent Ridge Rd, Singapore 119074, Republic of Singapore
| | - Y L Thian
- Department of Diagnostic Radiology, National University Hospital, Singapore, 5 Lower Kent Ridge Rd, Singapore 119074, Republic of Singapore
| | - B A Choo
- Department of Radiation Oncology, National University Cancer Institute, Singapore, 5 Lower Kent Ridge Rd, Singapore 119074, Republic of Singapore
| | - D Lim
- Department of Pathology, National University Hospital, Singapore, 5 Lower Kent Ridge Rd, Singapore 119074, Republic of Singapore
| | - Y W Lim
- Department of Hematology-Oncology, National University Cancer Institute, Singapore, 5 Lower Kent Ridge Rd, Singapore 119074, Republic of Singapore
| | - S E Lim
- Department of Hematology-Oncology, National University Cancer Institute, Singapore, 5 Lower Kent Ridge Rd, Singapore 119074, Republic of Singapore
| | - A Ilancheran
- Division of Gynecology-Oncology, Department of Obstetrics and Gynecology, National University Hospital, Singapore, 5 Lower Kent Ridge Rd, Singapore 119074, Republic of Singapore
| | - R Soong
- Cancer Science Institute of Singapore, National University of Singapore, 14 Medical Drive, Singapore 117599, Republic of Singapore.,Department of Pathology, National University Hospital, Singapore, 5 Lower Kent Ridge Rd, Singapore 119074, Republic of Singapore
| | - D S P Tan
- Department of Hematology-Oncology, National University Cancer Institute, Singapore, 5 Lower Kent Ridge Rd, Singapore 119074, Republic of Singapore.,Cancer Science Institute of Singapore, National University of Singapore, 14 Medical Drive, Singapore 117599, Republic of Singapore
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Shin SY, Jang S, Park CJ, Chi HS, Lee JH, Lee JH, Lee KH, Suh C, Lim SE, Seo EJ. Application of an immune-magnetic cell sorting method for CD138-positive plasma cells in FISH analysis of multiple myeloma. Int J Lab Hematol 2012; 34:541-6. [PMID: 22672327 DOI: 10.1111/j.1751-553x.2012.01433.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
INTRODUCTION Interphase fluorescence in situ hybridization (FISH) analysis of multiple myeloma (MM) may indiscriminately count signals of nonplasma cells, thus decreasing specificity and sensitivity. We aimed to evaluate the usefulness of an immune-magnetic sorting method for plasma cells in FISH analysis of MM and define optimal sample preparation conditions. METHODS Plasma cells were purified using EasySep(®) CD138 Positive Selection Cocktail and Magnetic Nanoparticles (Invitrogen). We compared FISH results with and without plasma cell purification for three sample preparation methods: direct harvest, 24-h culture, and 96-h culture with interleukin-4 in five newly diagnosed MM patients. Archived fixed bone marrow cells of 17 MM patients were also studied. RESULTS The percentage of abnormal cells identified was significantly higher with plasma cell purification than without purification (median, 88.0%; range, 84.0-100.0%vs. 15.0%, 12.5-29.5%, respectively). The three sample preparation methods showed comparable results. Immune-magnetic sorting also significantly increased the percentage of abnormal cells identified in FISH analysis of archived fixed bone marrow cells (P < 0.001). CONCLUSIONS Immune-magnetic CD138-positive cell sorting significantly increased the percentage of abnormal cells identified in FISH analysis of MM samples for all sample preparation methods. This method could also be applied for retrospective FISH analysis of archived fixed bone marrow cells.
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Affiliation(s)
- S Y Shin
- Department of Laboratory Medicine, University of Ulsan College of Medicine and Asan Medical Center, Seoul, Korea
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Luo N, Fones CSL, Lim SE, Xie F, Thumboo J, Li SC. The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-c30): validation of English version in Singapore. Qual Life Res 2005; 14:1181-6. [PMID: 16041912 DOI: 10.1007/s11136-004-4782-z] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
OBJECTIVE This study aimed to validate the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30, English version 3.0) in Singaporean cancer patients. METHODS In a cross-sectional study, a heterogeneous sample of cancer patients (n = 57) self-administered a questionnaire containing the QLQ-C30, the Short Form 36 Health Survey (SF-36) and assessing health and sociodemographic status. Construct validity was assessed by testing a priori hypotheses that QLQ-C30 scales would be moderately or strongly correlated with SF-36 scales measuring similar dimensions of health-related quality of life (HRQoL) and that subjects reporting mild symptoms would have better HRQoL scores than those reporting severe symptoms. Internal consistency reliability was assessed using Cronbach's alpha. RESULTS Strength of Spearman's correlations between the QLQ-C30 and SF-36 scales assessing similar dimensions of HRQoL ranged from 0.35 to 0.67. Subjects with mild symptoms had better scores than those with severe symptoms for all six QLQ-C30 HRQoL scales (p < 0.05 for five scales, Mann-Whitney U tests). Cronbach's alpha ranged from 0.19 for the cognitive functioning scale to 0.91 for the global QoL scale. CONCLUSION This study provides preliminary evidence for the validity and reliability of the EORTC QLQ-C30 in English-speaking Singaporean cancer patients.
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Affiliation(s)
- N Luo
- Department of Pharmacy, National University of Singapore, Singapore
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Abstract
Mitochondrial toxicity can result from antiviral nucleotide analog therapy used to control human immunodeficiency virus type 1 infection. We evaluated the ability of such analogs to inhibit DNA synthesis by the human mitochondrial DNA polymerase (pol gamma) by comparing the insertion and exonucleolytic removal of six antiviral nucleotide analogs. Apparent steady-state K(m) and k(cat) values for insertion of 2',3'-dideoxy-TTP (ddTTP), 3'-azido-TTP (AZT-TP), 2',3'-dideoxy-CTP (ddCTP), 2',3'-didehydro-TTP (D4T-TP), (-)-2',3'-dideoxy-3'-thiacytidine (3TC-TP), and carbocyclic 2',3'-didehydro-ddGTP (CBV-TP) indicated incorporation of all six analogs, albeit with varying efficiencies. Dideoxynucleotides and D4T-TP were utilized by pol gamma in vitro as efficiently as natural deoxynucleotides, whereas AZT-TP, 3TC-TP, and CBV-TP were only moderate inhibitors of DNA chain elongation. Inefficient excision of dideoxynucleotides, D4T, AZT, and CBV from DNA predicts persistence in vivo following successful incorporation. In contrast, removal of 3'-terminal 3TC residues was 50% as efficient as natural 3' termini. Finally, we observed inhibition of exonuclease activity by concentrations of AZT-monophosphate known to occur in cells. Thus, although their greatest inhibitory effects are through incorporation and chain termination, persistence of these analogs in DNA and inhibition of exonucleolytic proofreading may also contribute to mitochondrial toxicity.
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Affiliation(s)
- S E Lim
- Laboratory of Molecular Genetics, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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Lim SE, Longley MJ, Copeland WC. The mitochondrial p55 accessory subunit of human DNA polymerase gamma enhances DNA binding, promotes processive DNA synthesis, and confers N-ethylmaleimide resistance. J Biol Chem 1999; 274:38197-203. [PMID: 10608893 DOI: 10.1074/jbc.274.53.38197] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human DNA polymerase gamma is composed of a 140-kDa catalytic subunit and a smaller accessory protein variously reported to be 43-54 kDa. Immunoblot analysis of the purified, heterodimeric native human polymerase gamma complex identified the accessory subunit as 55 kDa. We isolated the full-length cDNA encoding a 55-kDa polypeptide, expressed the cDNA in Escherichia coli and purified the 55-kDa protein to homogeneity. Recombinant Hp55 forms a high affinity, salt-stable complex with Hp140 during protein affinity chromatography. Immunoprecipitation, gel filtration, and sedimentation analyses revealed a 190-kDa complex indicative of a native heterodimer. Reconstitution of Hp140.Hp55 raises the salt optimum of Hp140, stimulates the polymerase and exonuclease activities, and increases the processivity of the enzyme by several 100-fold. Similar to Hp140, isolated Hp55 binds DNA with moderate strength and was a specificity for double-stranded primer-template DNA. However, Hp140.Hp55 has a surprisingly high affinity for DNA, and kinetic analyses indicate Hp55 enhances the affinity of Hp140 for primer termini by 2 orders of magnitude. Thus the enhanced DNA binding caused by Hp55 is the basis for the salt tolerance and high processivity characteristic of DNA polymerase gamma. Observation of native DNA polymerase gamma both as an Hp140 monomer and as a heterodimer with Hp55 supports the notion that the two forms act in mitochondrial DNA repair and replication. Additionally, association of Hp55 with Hp140 protects the polymerase from inhibition by N-ethylmaleimide.
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Affiliation(s)
- S E Lim
- Laboratory of Molecular Genetics, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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10
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Vaisman A, Lim SE, Patrick SM, Copeland WC, Hinkle DC, Turchi JJ, Chaney SG. Effect of DNA polymerases and high mobility group protein 1 on the carrier ligand specificity for translesion synthesis past platinum-DNA adducts. Biochemistry 1999; 38:11026-39. [PMID: 10460158 DOI: 10.1021/bi9909187] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Translesion synthesis past Pt-DNA adducts can affect both the cytotoxicity and mutagenicity of the platinum adducts. We have shown previously that the extent of replicative bypass in vivo is influenced by the carrier ligand of platinum adducts. The specificity of replicative bypass may be determined by the DNA polymerase complexes that catalyze translesion synthesis past Pt-DNA adducts and/or by DNA damage-recognition proteins that bind to the Pt-DNA adducts and block translesion replication. In the present study, primer extension on DNA templates containing site-specifically placed cisplatin, oxaliplatin, JM216, or chlorodiethylenetriamine-Pt adducts revealed that the eukaryotic DNA polymerases beta, zeta, gamma, and human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) had a similar specificity for translesion synthesis past Pt-DNA adducts (dien >> oxaliplatin >/= cisplatin > JM216). Primer extension assays performed in the presence of high mobility group protein 1 (HMG1), which is known to recognize cisplatin-damaged DNA, revealed that inhibition of translesion synthesis by HMG1 also depended on the carrier ligand of the Pt-DNA adduct (cisplatin > oxaliplatin = JM216 >> dien). These data were consistent with the results of gel-shift experiments showing similar differences in the affinity of HMG1 for DNA modified with the different platinum adducts. Our studies show that both DNA polymerases and damage-recognition proteins can impart specificity to replicative bypass of Pt-DNA adducts. This information may serve as a model for further studies of translesion synthesis.
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Affiliation(s)
- A Vaisman
- Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, School of Medicine, University of North Carolina, Chapel Hill 27599-7260, USA
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Carrodeguas JA, Kobayashi R, Lim SE, Copeland WC, Bogenhagen DF. The accessory subunit of Xenopus laevis mitochondrial DNA polymerase gamma increases processivity of the catalytic subunit of human DNA polymerase gamma and is related to class II aminoacyl-tRNA synthetases. Mol Cell Biol 1999; 19:4039-46. [PMID: 10330144 PMCID: PMC104363 DOI: 10.1128/mcb.19.6.4039] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Peptide sequences obtained from the accessory subunit of Xenopus laevis mitochondrial DNA (mtDNA) polymerase gamma (pol gamma) were used to clone the cDNA encoding this protein. Amino-terminal sequencing of the mitochondrial protein indicated the presence of a 44-amino-acid mitochondrial targeting sequence, leaving a predicted mature protein with 419 amino acids and a molecular mass of 47.3 kDa. This protein is associated with the larger, catalytic subunit in preparations of active mtDNA polymerase. The small subunit exhibits homology to its human, mouse, and Drosophila counterparts. Interestingly, significant homology to glycyl-tRNA synthetases from prokaryotic organisms reveals a likely evolutionary relationship. Since attempts to produce an enzymatically active recombinant catalytic subunit of Xenopus DNA pol gamma have not been successful, we tested the effects of adding the small subunit of the Xenopus enzyme to the catalytic subunit of human DNA pol gamma purified from baculovirus-infected insect cells. These experiments provide the first functional evidence that the small subunit of DNA pol gamma stimulates processive DNA synthesis by the human catalytic subunit under physiological salt conditions.
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Affiliation(s)
- J A Carrodeguas
- Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York 11794-8651, USA
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12
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Longley MJ, Ropp PA, Lim SE, Copeland WC. Characterization of the native and recombinant catalytic subunit of human DNA polymerase gamma: identification of residues critical for exonuclease activity and dideoxynucleotide sensitivity. Biochemistry 1998; 37:10529-39. [PMID: 9671525 DOI: 10.1021/bi980772w] [Citation(s) in RCA: 137] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The human DNA polymerase gamma catalytic subunit was overexpressed in recombinant baculovirus-infected insect cells, and the 136 000 Da protein was purified to homogeneity. Application of the same purification protocol to HeLa mitochondrial lysates permitted isolation of native DNA polymerase gamma as a single subunit, allowing direct comparison of the native and recombinant enzymes without interference of other polypeptides. Both forms exhibited identical properties, and the DNA polymerase and 3' --> 5' exonuclease activities were shown unambiguously to reside in the catalytic polypeptide. The salt sensitivity and moderate processivity of the isolated catalytic subunit suggest other factors could be required to restore the salt tolerance and highly processive DNA synthesis typical of gamma polymerases. To facilitate our understanding of mitochondrial DNA replication and mutagenesis as well as cytotoxicity mediated by antiviral nucleotide analogues, we also constructed two site-directed mutant proteins of the human DNA polymerase gamma. Substituting alanine for two essential acidic residues in the exonuclease motif selectively eliminated the 3' --> 5' exonucleolytic function of the purified mutant polymerase gamma. Replacement of a tyrosine residue critical for sugar recognition with phenylalanine in polymerase motif B reduced dideoxynucleotide inhibition by a factor of 5000 with only minor effects on overall polymerase function.
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Affiliation(s)
- M J Longley
- Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA
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Oleykowski CA, Mayernik JA, Lim SE, Groopman JD, Grossman L, Wogan GN, Yeung AT. Repair of aflatoxin B1 DNA adducts by the UvrABC endonuclease of Escherichia coli. J Biol Chem 1993; 268:7990-8002. [PMID: 8463319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The repair by UvrABC endonuclease of two major adducts formed by aflatoxin B1 in DNA was found to be similar. Aflatoxin epoxide was used to generate the aflatoxin B1.N7-guanine adduct which can convert to aflatoxin B1-formamidopyrimidine adduct. The reaction of the aflatoxin B1 epoxide with DNA follows pseudo-first order kinetics. The DNA sequence-specific relative reactivity of the epoxide is the same as previously observed for aflatoxin B1 activated by liver microsomes, therefore strongly reinforcing the notion that aflatoxin B1 reacts with DNA through the epoxide intermediate. For the majority of lesion sites, a high affinity protein-DNA complex was formed from the UvrA and the UvrB proteins with similar efficiency to both adducts, and to pyrimidine dimers, and then nicks the DNA when UvrC was added. The two incisions are at the eighth phosphodiester moiety 5' and the sixth phosphodiester moiety 3' of a modified guanine nucleotide. Both incisions appeared to be concerted. For some sites, the DNA sequence can alter the relative incision efficiency up to 15-fold. However, the majority of these AFB1 lesion structures in most DNA sequences are similar with respect to recognition by this nucleotide excision repair enzyme. Therefore the observation that the aflatoxin B1.N7-guanine lesion is removed rapidly, while the aflatoxin B1-formamidopyrimidine lesion persists in the mammalian cell may have other mechanistic explanations.
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Affiliation(s)
- C A Oleykowski
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111
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Levy DD, Groopman JD, Lim SE, Seidman MM, Kraemer KH. Sequence specificity of aflatoxin B1-induced mutations in a plasmid replicated in xeroderma pigmentosum and DNA repair proficient human cells. Cancer Res 1992; 52:5668-73. [PMID: 1394191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The mutagenic spectrum induced by aflatoxin-DNA lesions in DNA repair deficient and repair proficient human cells was investigated. The reactive metabolite aflatoxin B1-8,9-epoxide was synthesized and reacted in vitro with the shuttle vector plasmid pS189. Plasmids were transfected into human fibroblasts and allowed to replicate, and the recovered plasmids were screened in indicator bacteria for plasmid survival and mutations in the supF marker gene. Sequence data were obtained from 71 independently arising mutants recovered from DNA repair deficient xeroderma pigmentosum (XP) cells [XP12BE(SV40)] and 60 mutants recovered from a DNA repair proficient cell line (GM0637). Plasmid survival was lower and mutation frequency higher with the XP cells, and the mutation hotspots differed substantially for the 2 cell lines. Most mutations (> 90%) were base substitutions at G:C pairs, only about one-half of which were G:C-->T:A transversions, the expected predominant mutation. One-third of the mutations at GG sites and none of those at isolated Gs were G:C-->A:T transitions. Tandem base substitutions also occurred only at GG sites and were found only with XP cells. The location of mutation hotspots with either cell line did not correlate with the level of modification within the sequence as assessed by a DNA polymerase stop assay. These results suggest that the DNA repair deficiency associated with XP can influence not only the overall frequency of mutations but also the distribution of mutations within a gene. The finding of transition mutations exclusively at GG sites may be of predictive value in attempts to link dietary aflatoxin exposure to cancers associated with specific mutations in the c-ras oncogene and the p53 tumor suppressor gene.
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Affiliation(s)
- D D Levy
- Laboratory of Molecular Carcinogenesis, National Cancer Institute, Bethesda, Maryland 20892
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Affiliation(s)
- M K Sim
- Department of Pharmacology, Faculty of Medicine, National University of Singapore
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