1
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Norris JL, Rogers LO, Pytko KG, Dannenberg RL, Perreault S, Kaushik V, Kuppa S, Antony E, Hedglin M. Replication protein A dynamically re-organizes on primer/template junctions to permit DNA polymerase δ holoenzyme assembly and initiation of DNA synthesis. Nucleic Acids Res 2024:gkae475. [PMID: 38842913 DOI: 10.1093/nar/gkae475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 05/03/2024] [Accepted: 05/21/2024] [Indexed: 06/07/2024] Open
Abstract
DNA polymerase δ (pol δ) holoenzymes, comprised of pol δ and the processivity sliding clamp, PCNA, carry out DNA synthesis during lagging strand replication, initiation of leading strand replication, and the major DNA damage repair and tolerance pathways. Pol δ holoenzymes are assembled at primer/template (P/T) junctions and initiate DNA synthesis in a stepwise process involving the major single strand DNA (ssDNA)-binding protein complex, RPA, the processivity sliding clamp loader, RFC, PCNA and pol δ. During this process, the interactions of RPA, RFC and pol δ with a P/T junction all significantly overlap. A burning issue that has yet to be resolved is how these overlapping interactions are accommodated during this process. To address this, we design and utilize novel, ensemble FRET assays that continuously monitor the interactions of RPA, RFC, PCNA and pol δ with DNA as pol δ holoenzymes are assembled and initiate DNA synthesis. Results from the present study reveal that RPA remains engaged with P/T junctions throughout this process and the RPA•DNA complexes dynamically re-organize to allow successive binding of RFC and pol δ. These results have broad implications as they highlight and distinguish the functional consequences of dynamic RPA•DNA interactions in RPA-dependent DNA metabolic processes.
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Affiliation(s)
- Jessica L Norris
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
| | - Lindsey O Rogers
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
| | - Kara G Pytko
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
| | - Rachel L Dannenberg
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
| | - Samuel Perreault
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
| | - Vikas Kaushik
- The Saint Louis University School of Medicine, Department of Biochemistry and Molecular Biology, St. Louis, MO 63104, USA
| | - Sahiti Kuppa
- The Saint Louis University School of Medicine, Department of Biochemistry and Molecular Biology, St. Louis, MO 63104, USA
| | - Edwin Antony
- The Saint Louis University School of Medicine, Department of Biochemistry and Molecular Biology, St. Louis, MO 63104, USA
| | - Mark Hedglin
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
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2
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Islam T, Josephs EA. Genome editing outcomes reveal mycobacterial NucS participates in a short-patch repair of DNA mismatches. Nucleic Acids Res 2024:gkae402. [PMID: 38747340 DOI: 10.1093/nar/gkae402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Revised: 04/24/2024] [Accepted: 05/01/2024] [Indexed: 05/28/2024] Open
Abstract
In the canonical DNA mismatch repair (MMR) mechanism in bacteria, if a nucleotide is incorrectly mis-paired with the template strand during replication, the resulting repair of this mis-pair can result in the degradation and re-synthesis of hundreds or thousands of nucleotides on the newly-replicated strand (long-patch repair). While mycobacteria, which include important pathogens such as Mycobacterium tuberculosis, lack the otherwise highly-conserved enzymes required for the canonical MMR reaction, it was found that disruption of a mycobacterial mismatch-sensitive endonuclease NucS results in a hyper-mutative phenotype, leading to the idea that NucS might be involved in a cryptic, independently-evolved DNA MMR mechanism, perhaps mediated by homologous recombination (HR) with a sister chromatid. Using oligonucleotide recombination, which allows us to introduce mismatches specifically into the genomes of a model for M. tuberculosis, Mycobacterium smegmatis, we find that NucS participates in a direct repair of DNA mismatches where the patch of excised nucleotides is largely confined to within ∼5-6 bp of the mis-paired nucleotides, which is inconsistent with mechanistic models of canonical mycobacterial HR or other double-strand break (DSB) repair reactions. The results presented provide evidence of a novel NucS-associated mycobacterial MMR mechanism occurring in vivo to regulate genetic mutations in mycobacteria.
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Affiliation(s)
- Tanjina Islam
- Department of Nanoscience, University of North Carolina at Greensboro, Greensboro, NC 27401, USA
| | - Eric A Josephs
- Department of Nanoscience, University of North Carolina at Greensboro, Greensboro, NC 27401, USA
- Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27401, USA
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3
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Neven J, Issayama LK, Dewachter I, Wilson DM. Genomic stress and impaired DNA repair in Alzheimer disease. DNA Repair (Amst) 2024; 139:103678. [PMID: 38669748 DOI: 10.1016/j.dnarep.2024.103678] [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: 02/07/2024] [Accepted: 04/06/2024] [Indexed: 04/28/2024]
Abstract
Alzheimer disease (AD) is the most prominent form of dementia and has received considerable attention due to its growing burden on economic, healthcare and basic societal infrastructures. The two major neuropathological hallmarks of AD, i.e., extracellular amyloid beta (Aβ) peptide plaques and intracellular hyperphosphorylated Tau neurofibrillary tangles, have been the focus of much research, with an eye on understanding underlying disease mechanisms and identifying novel therapeutic avenues. One often overlooked aspect of AD is how Aβ and Tau may, through indirect and direct mechanisms, affect genome integrity. Herein, we review evidence that Aβ and Tau abnormalities induce excessive genomic stress and impair genome maintenance mechanisms, events that can promote DNA damage-induced neuronal cell loss and associated brain atrophy.
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Affiliation(s)
- Jolien Neven
- Hasselt University, Biomedical Research Institute, BIOMED, Hasselt 3500, Belgium
| | - Luidy Kazuo Issayama
- Hasselt University, Biomedical Research Institute, BIOMED, Hasselt 3500, Belgium
| | - Ilse Dewachter
- Hasselt University, Biomedical Research Institute, BIOMED, Hasselt 3500, Belgium
| | - David M Wilson
- Hasselt University, Biomedical Research Institute, BIOMED, Hasselt 3500, Belgium.
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4
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Sobol RW. Mouse models to explore the biological and organismic role of DNA polymerase beta. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2024; 65 Suppl 1:57-71. [PMID: 38619421 PMCID: PMC11027944 DOI: 10.1002/em.22593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 03/14/2024] [Accepted: 03/19/2024] [Indexed: 04/16/2024]
Abstract
Gene knock-out (KO) mouse models for DNA polymerase beta (Polβ) revealed that loss of Polβ leads to neonatal lethality, highlighting the critical organismic role for this DNA polymerase. While biochemical analysis and gene KO cell lines have confirmed its biochemical role in base excision repair and in TET-mediated demethylation, more long-lived mouse models continue to be developed to further define its organismic role. The Polb-KO mouse was the first of the Cre-mediated tissue-specific KO mouse models. This technology was exploited to investigate roles for Polβ in V(D)J recombination (variable-diversity-joining rearrangement), DNA demethylation, gene complementation, SPO11-induced DNA double-strand break repair, germ cell genome stability, as well as neuronal differentiation, susceptibility to genotoxin-induced DNA damage, and cancer onset. The revolution in knock-in (KI) mouse models was made possible by CRISPR/cas9-mediated gene editing directly in C57BL/6 zygotes. This technology has helped identify phenotypes associated with germline or somatic mutants of Polβ. Such KI mouse models have helped uncover the importance of key Polβ active site residues or specific Polβ enzyme activities, such as the PolbY265C mouse that develops lupus symptoms. More recently, we have used this KI technology to mutate the Polb gene with two codon changes, yielding the PolbL301R/V303R mouse. In this KI mouse model, the expressed Polβ protein cannot bind to its obligate heterodimer partner, Xrcc1. Although the expressed mutant Polβ protein is proteolytically unstable and defective in recruitment to sites of DNA damage, the homozygous PolbL301R/V303R mouse is viable and fertile, yet small in stature. We expect that this and additional targeted mouse models under development are poised to reveal new biological and organismic roles for Polβ.
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Affiliation(s)
- Robert W. Sobol
- Department of Pathology and Laboratory Medicine, Warren Alpert Medical School & Legorreta Cancer Center, Brown University, Providence, RI 02912
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5
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Guo J, Tang B, Fu J, Zhu X, Xie W, Wang N, Ding Z, Song Z, Yang Y, Xu G, Xiao X. High-plex spatial transcriptomic profiling reveals distinct immune components and the HLA class I/DNMT3A/CD8 modulatory axis in mismatch repair-deficient endometrial cancer. Cell Oncol (Dordr) 2024; 47:573-585. [PMID: 37847338 PMCID: PMC11090934 DOI: 10.1007/s13402-023-00885-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2023] [Indexed: 10/18/2023] Open
Abstract
PURPOSE Tumors bearing mismatch repair deficiency (MMRd) are characterized by a high load of neoantigens and are believed to trigger immunogenic reactions upon immune checkpoint blockade treatment such as anti-PD-1/PD-L1 therapy. However, the mechanisms are still ill-defined, as multiple cancers with MMRd exhibit variable responses to immune checkpoint inhibitors (ICIs). In endometrial cancer (EC), a distinct tumor microenvironment (TME) exists that may correspond to treatment-related efficacies. We aimed to characterize EC patients with aberrant MMR pathways to identify molecular subtypes predisposed to respond to ICI therapies. METHODS We applied digital spatial profiling, a high-plex spatial transcriptomic approach covering over 1,800 genes, to obtain a highly resolved TME landscape in 45 MMRd-EC patients. We cross-validated multiple biomarkers identified using immunohistochemistry and multiplexed immunofluorescence using in-study and independent cohorts totaling 123 MMRd-EC patients and validated our findings using external TCGA data from microsatellite instability endometrial cancer (MSI-EC) patients. RESULTS High-plex spatial profiling identified a 14-gene signature in the MMRd tumor-enriched regions stratifying tumors into "hot", "intermediate" and "cold" groups according to their distinct immune profiles, a finding highly consistent with the corresponding CD8 + T-cell infiltration status. Our validation studies further corroborated an existing coregulatory network involving HLA class I and DNMT3A potentially bridged through dynamic crosstalk incorporating CCL5. CONCLUSION Our study confirmed the heterogeneous TME status within MMRd-ECs and showed that these ECs can be stratified based on potential biomarkers such as HLA class I, DNMT3A and CD8 in pathological settings for improved ICI therapeutic efficacy in this subset of patients.
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Affiliation(s)
- Jingjing Guo
- Department of Pathology, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
- School of Medical and Life Sciences, Chengdu University of TCM, Chengdu, China
| | - Baijie Tang
- Department of Pathology, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Jing Fu
- Department of Pathology, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Xuan Zhu
- Department of Pathology, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
- School of Medical and Life Sciences, Chengdu University of TCM, Chengdu, China
| | - Wenlong Xie
- Department of Pathology, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
- School of Medical and Life Sciences, Chengdu University of TCM, Chengdu, China
| | - Nan Wang
- Mills Institute for Personalized Cancer Care, Jinan, China
| | - Zhiyong Ding
- Mills Institute for Personalized Cancer Care, Jinan, China
| | - Zhentao Song
- Mills Institute for Personalized Cancer Care, Jinan, China
| | - Yue Yang
- Department of Pathology, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Gang Xu
- Department of Pathology, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China
| | - Xue Xiao
- Department of Pathology, Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, China.
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6
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Kim-Yip RP, McNulty R, Joyce B, Mollica A, Chen PJ, Ravisankar P, Law BK, Liu DR, Toettcher JE, Ivakine EA, Posfai E, Adamson B. Efficient prime editing in two-cell mouse embryos using PEmbryo. Nat Biotechnol 2024:10.1038/s41587-023-02106-x. [PMID: 38321114 DOI: 10.1038/s41587-023-02106-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 12/14/2023] [Indexed: 02/08/2024]
Abstract
Using transient inhibition of DNA mismatch repair during a permissive stage of development, we demonstrate highly efficient prime editing of mouse embryos with few unwanted, local byproducts (average 58% precise edit frequency, 0.5% on-target error frequency across 13 substitution edits at 8 sites), enabling same-generation phenotyping of founders. Whole-genome sequencing reveals that mismatch repair inhibition increases off-target indels at low-complexity regions in the genome without any obvious phenotype in mice.
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Affiliation(s)
- Rebecca P Kim-Yip
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Ryan McNulty
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
| | - Bradley Joyce
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Antonio Mollica
- Genetics and Genome Biology Program, The Hospital for Sick Children, Toronto, ON, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Peter J Chen
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA
- Prime Medicine, Inc., Cambridge, MA, USA
| | - Purnima Ravisankar
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
- Immunology and Microbial Pathogenesis Program, Weill Cornell Graduate School of Medical Sciences, New York, NY, USA
| | - Benjamin K Law
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA
| | - David R Liu
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA
| | - Jared E Toettcher
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Evgueni A Ivakine
- Genetics and Genome Biology Program, The Hospital for Sick Children, Toronto, ON, Canada
- Department of Physiology, University of Toronto, Toronto, ON, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Eszter Posfai
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
| | - Britt Adamson
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA.
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7
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Liu J, Li J, Luo F, Wu S, Li B, Liu K. The Predictive Value of CD3+/CD8+ Lymphocyte Infiltration and PD-L1 Expression in Colorectal Cancer. Curr Oncol 2023; 30:9647-9659. [PMID: 37999119 PMCID: PMC10670477 DOI: 10.3390/curroncol30110699] [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: 08/24/2023] [Revised: 10/20/2023] [Accepted: 10/20/2023] [Indexed: 11/25/2023] Open
Abstract
AIM The immune system plays an important role in tumor development and treatment. In this study, we aimed to determine the relationships among the expressions of PD-L1, CD3, CD8, MMR proteins, clinicopathological features, and prognosis of CRC. METHODS Immunohistochemistry was used to determine the expression of PD-L1, CD3, and CD8 in 771 patients with CRC. RESULTS The expression of PD-L1 in TC was related to the right colon, adenocarcinoma, and dMMR, and in IC, it was related to younger CRC patients and the TNM stage. The expression of CD3 and CD8 in tumor-infiltrating lymphocytes was related to lymph node metastasis and the TNM stage. The expression of PD-L1 in TC and IC was correlated with the infiltration of CD3+ and CD8+ lymphocytes. Univariate survival analysis showed that the expression of PD-L1 in TC, IC, and dMMR was related to a better prognosis. Multivariate survival analysis showed that age, TNM stage, and dMMR were independent prognostic factors for CRC. The OS of the chemotherapy was significantly higher than that of the non-chemotherapy in III-IV TNM stage patients; CRC patients with positive PD-L1 expression in TC or IC and dMMR did not benefit from chemotherapy. CONCLUSIONS PD-L1 expression in TC and IC was closely related to the density of CD3 and CD8 infiltration in tumor-infiltrating lymphocytes. The expression of CD3 and CD8 in tumor-infiltrating lymphocytes and the expression of PD-L1 in IC were linked to the TNM stage of CRC patients. PD-L1 expression in TC and IC and MMR status may act as an important biomarker for guiding the postoperative treatment of III-IV TNM stage CRC patients.
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Affiliation(s)
| | | | | | | | | | - Kunping Liu
- Department of Pathology, The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People’s Hospital, Qingyuan 511518, China
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8
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Islam T, Josephs EA. Genome Editing Outcomes Reveal Mycobacterial NucS Participates in a Short-Patch Repair of DNA Mismatches. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.23.563644. [PMID: 37961639 PMCID: PMC10634747 DOI: 10.1101/2023.10.23.563644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
In the canonical DNA mismatch repair (MMR) mechanism in bacteria, if during replication a nucleotide is incorrectly mis-paired with the template strand, the resulting repair of this mis-pair can result in the degradation and re-synthesis of hundreds or thousands of nucleotides on the newly-replicated strand (long-patch repair). While mycobacteria, which include important pathogens such as Mycobacterium tuberculosis, lack the otherwise highly-conserved enzymes required for the canonical MMR reaction, it was found that disruption of a mycobacterial mismatch-sensitive endonuclease NucS results in a hyper-mutative phenotype, which has led to the idea that NucS might be involved in a cryptic, independently-evolved DNA MMR mechanism. It has been proposed that nuclease activity at a mismatch might result in correction by homologous recombination (HR) with a sister chromatid. Using oligonucleotide recombination, which allows us to introduce mismatches during replication specifically into the genomes of a model for M. tuberculosis, Mycobacterium smegmatis, we find that NucS participates in a direct repair of DNA mismatches where the patch of excised nucleotides is largely confined to within ~5 - 6 bp of the mis-paired nucleotides, which is inconsistent with mechanistic models of canonical mycobacterial HR or other double-strand break (DSB) repair reactions. The results presented provide evidence of a novel NucS-associated mycobacterial MMR mechanism occurring in vivo to regulate genetic mutations in mycobacteria.
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Affiliation(s)
- Tanjina Islam
- Department of Nanoscience, University of North Carolina at Greensboro, Greensboro, NC, 27401, USA
| | - Eric A. Josephs
- Department of Nanoscience, University of North Carolina at Greensboro, Greensboro, NC, 27401, USA
- Department of Biology, University of North Carolina at Greensboro, Greensboro, NC, 27401, USA
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9
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Iwata T, Kurahashi Y, Wijaya IMM, Kandori H. Spectroscopic Investigation of Na +-Dependent Conformational Changes of a Cyclobutane Pyrimidine Dimer-Repairing Deoxyribozyme. ACS OMEGA 2023; 8:37274-37281. [PMID: 37841180 PMCID: PMC10569015 DOI: 10.1021/acsomega.3c05083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Accepted: 09/19/2023] [Indexed: 10/17/2023]
Abstract
UV1C is an enzymatically active DNA sequence (deoxyribozyme, DNAzyme) that functions as a cyclobutane pyrimidine dimer (CPD) photolyase. UV1C forms parallel guanine quadruplexes (G-quadruplexes) with a DNA substrate in the presence of 240 mM Na+, the structure of which is important for the enzymatic activity. To investigate the repair mechanism of CPD by UV1C, we designed light-induced Fourier transform infrared (FTIR) spectroscopy. Prior to FTIR measurements, circular dichroism (CD) spectroscopy was conducted to determine the Na+ concentration at which the most G-quadruplexes were formed. We found that UV1C also forms a hybrid G-quadruplex structure at over 500 mM Na+. By assuming a concentration equilibrium between G-quadruplexes and Na+, 1.3 and 1.8 Na+ were found to bind to parallel and hybrid G-quadruplexes, respectively. The hybrid G-quadruplex form of UV1C was also suggested to exhibit photolyase activity. Light-induced FTIR spectra recorded upon the photorepair of CPD by UV1C were compared for parallel G-quadruplex-rich and hybrid G-quadruplex-rich samples. Spectral variations were indicative of structural differences in parallel and hybrid G-quadruplexes before and after CPD cleavage. Differences were also observed when compared to the CPD repair spectrum by CPD photolyase. The spectral differences during CPD repair by either protein or DNAzyme suggest the local environment of the substrates, the surrounding protein, or the aqueous solution.
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Affiliation(s)
- Tatsuya Iwata
- Department
of Pharmaceutical Sciences, Toho University, Funabashi, Chiba 274-8510, Japan
| | - Yuhi Kurahashi
- Department
of Life Science and Applied Chemistry, Nagoya
Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - I Made Mahaputra Wijaya
- Department
of Life Science and Applied Chemistry, Nagoya
Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Hideki Kandori
- Department
of Life Science and Applied Chemistry, Nagoya
Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
- OptoBioTechnology
Research Center, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
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10
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Zeng Z, Gu J, Lin S, Li Q, Wang W, Guo Y. Molecular basis of the phenotypic variants arising from a Pseudoalteromonas lipolytica mutator. Microb Genom 2023; 9:001118. [PMID: 37850970 PMCID: PMC10634453 DOI: 10.1099/mgen.0.001118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 10/04/2023] [Indexed: 10/19/2023] Open
Abstract
Bacterial deficiencies in the DNA repair system can produce mutator strains that promote adaptive microevolution. However, the role of mutator strains in marine Pseudoalteromonas, capable of generating various gain-of-function genetic variants within biofilms, remains largely unknown. In this study, inactivation of mutS in Pseudoalteromonas lipolytica conferred an approximately 100-fold increased resistance to various antibiotics, including ciprofloxacin, rifampicin and aminoglycoside. Furthermore, the mutator of P. lipolytica generated variants that displayed enhanced biofilm formation but reduced swimming motility, indicating a high phenotypic diversity within the ΔmutS population. Additionally, we observed a significant production rate of approximately 50 % for the translucent variants, which play important roles in biofilm formation, when the ΔmutS strain was cultured on agar plates or under shaking conditions. Using whole-genome deep-sequencing combined with genetic manipulation, we demonstrated that point mutations in AT00_17115 within the capsular biosynthesis cluster were responsible for the generation of translucent variants in the ΔmutS subpopulation, while mutations in flagellar genes fliI and flgP led to a decrease in swimming motility. Collectively, this study reveals a specific mutator-driven evolution in P. lipolytica, characterized by substantial genetic and phenotypic diversification, thereby offering a reservoir of genetic attributes associated with microbial fitness.
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Affiliation(s)
- Zhenshun Zeng
- Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, School of Environmental Science and Engineering, Guangzhou University, Guangzhou, PR China
| | - Jiayu Gu
- Key Laboratory of Tropical Marine Bio-Resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, PR China
- University of Chinese Academy of Sciences, Beijing, PR China
| | - Shituan Lin
- Key Laboratory of Tropical Marine Bio-Resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, PR China
- University of Chinese Academy of Sciences, Beijing, PR China
| | - Qian Li
- Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, School of Environmental Science and Engineering, Guangzhou University, Guangzhou, PR China
| | - Weiquan Wang
- Key Laboratory of Tropical Marine Bio-Resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, PR China
- University of Chinese Academy of Sciences, Beijing, PR China
| | - Yuexue Guo
- Key Laboratory of Tropical Marine Bio-Resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, PR China
- University of Chinese Academy of Sciences, Beijing, PR China
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11
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Wolf K, Kosinski J, Gibson TJ, Wesch N, Dötsch V, Genuardi M, Cordisco EL, Zeuzem S, Brieger A, Plotz G. A conserved motif in the disordered linker of human MLH1 is vital for DNA mismatch repair and its function is diminished by a cancer family mutation. Nucleic Acids Res 2023; 51:6307-6320. [PMID: 37224528 PMCID: PMC10325900 DOI: 10.1093/nar/gkad418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 04/26/2023] [Accepted: 05/17/2023] [Indexed: 05/26/2023] Open
Abstract
DNA mismatch repair (MMR) is essential for correction of DNA replication errors. Germline mutations of the human MMR gene MLH1 are the major cause of Lynch syndrome, a heritable cancer predisposition. In the MLH1 protein, a non-conserved, intrinsically disordered region connects two conserved, catalytically active structured domains of MLH1. This region has as yet been regarded as a flexible spacer, and missense alterations in this region have been considered non-pathogenic. However, we have identified and investigated a small motif (ConMot) in this linker which is conserved in eukaryotes. Deletion of the ConMot or scrambling of the motif abolished mismatch repair activity. A mutation from a cancer family within the motif (p.Arg385Pro) also inactivated MMR, suggesting that ConMot alterations can be causative for Lynch syndrome. Intriguingly, the mismatch repair defect of the ConMot variants could be restored by addition of a ConMot peptide containing the deleted sequence. This is the first instance of a DNA mismatch repair defect conferred by a mutation that can be overcome by addition of a small molecule. Based on the experimental data and AlphaFold2 predictions, we suggest that the ConMot may bind close to the C-terminal MLH1-PMS2 endonuclease and modulate its activation during the MMR process.
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Affiliation(s)
- Karla Wolf
- Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, 60590, Germany
| | - Jan Kosinski
- European Molecular Biology Laboratory (EMBL), Centre for Structural Systems Biology (CSSB), Hamburg, 22607, Germany
| | - Toby J Gibson
- European Molecular Biology Laboratory (EMBL), Structural and Computational Biology Unit, Heidelberg, 69117, Germany
| | - Nicole Wesch
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Frankfurt am Main, 60438, Germany
| | - Volker Dötsch
- Institute of Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University, Frankfurt am Main, 60438, Germany
| | - Maurizio Genuardi
- UOC Genetica Medica, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome00168, Italy
| | - Emanuela Lucci Cordisco
- Dipartimento di Scienze della Vita e di Sanità Pubblica, Università Cattolica del Sacro Cuore, Rome00168, Italy
| | - Stefan Zeuzem
- Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, 60590, Germany
| | - Angela Brieger
- Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, 60590, Germany
| | - Guido Plotz
- Department of Internal Medicine 1, University Hospital, Goethe University, Frankfurt am Main, 60590, Germany
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12
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Norris JL, Rogers LO, Pytko KG, Dannenberg RL, Perreault S, Kaushik V, Kuppa S, Antony E, Hedglin M. Interplay of macromolecular interactions during assembly of human DNA polymerase δ holoenzymes and initiation of DNA synthesis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.09.539896. [PMID: 37215012 PMCID: PMC10197535 DOI: 10.1101/2023.05.09.539896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In humans, DNA polymerase δ (Pol δ) holoenzymes, comprised of Pol δ and the processivity sliding clamp, proliferating cell nuclear antigen (PCNA), carry out DNA synthesis during lagging strand DNA replication, initiation of leading strand DNA replication, and the major DNA damage repair and tolerance pathways. Pol δ holoenzymes are assembled at primer/template (P/T) junctions and initiate DNA synthesis in a coordinated process involving the major single strand DNA-binding protein complex, replication protein A (RPA), the processivity sliding clamp loader, replication factor C (RFC), PCNA, and Pol δ. Each of these factors interact uniquely with a P/T junction and most directly engage one another. Currently, the interplay between these macromolecular interactions is largely unknown. In the present study, novel Förster Resonance Energy Transfer (FRET) assays reveal that dynamic interactions of RPA with a P/T junction during assembly of a Pol δ holoenzyme and initiation of DNA synthesis maintain RPA at a P/T junction and accommodate RFC, PCNA, and Pol δ, maximizing the efficiency of each process. Collectively, these studies significantly advance our understanding of human DNA replication and DNA repair.
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Affiliation(s)
- Jessica L. Norris
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
| | - Lindsey O. Rogers
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
| | - Kara G. Pytko
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
| | - Rachel L. Dannenberg
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
| | - Samuel Perreault
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
| | - Vikas Kaushik
- The Saint Louis University School of Medicine, Department of Biochemistry and Molecular Biology, St. Louis MO, 63104
| | - Sahiti Kuppa
- The Saint Louis University School of Medicine, Department of Biochemistry and Molecular Biology, St. Louis MO, 63104
| | - Edwin Antony
- The Saint Louis University School of Medicine, Department of Biochemistry and Molecular Biology, St. Louis MO, 63104
| | - Mark Hedglin
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
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13
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Narayanan S J J, Tripathi D, Verma P, Adhikary A, Dutta AK. Secondary Electron Attachment-Induced Radiation Damage to Genetic Materials. ACS OMEGA 2023; 8:10669-10689. [PMID: 37008102 PMCID: PMC10061531 DOI: 10.1021/acsomega.2c06776] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/23/2022] [Accepted: 02/20/2023] [Indexed: 06/19/2023]
Abstract
Reactions of radiation-produced secondary electrons (SEs) with biomacromolecules (e.g., DNA) are considered one of the primary causes of radiation-induced cell death. In this Review, we summarize the latest developments in the modeling of SE attachment-induced radiation damage. The initial attachment of electrons to genetic materials has traditionally been attributed to the temporary bound or resonance states. Recent studies have, however, indicated an alternative possibility with two steps. First, the dipole-bound states act as a doorway for electron capture. Subsequently, the electron gets transferred to the valence-bound state, in which the electron is localized on the nucleobase. The transfer from the dipole-bound to valence-bound state happens through a mixing of electronic and nuclear degrees of freedom. In the presence of aqueous media, the water-bound states act as the doorway state, which is similar to that of the presolvated electron. Electron transfer from the initial doorway state to the nucleobase-bound state in the presence of bulk aqueous media happens on an ultrafast time scale, and it can account for the decrease in DNA strand breaks in aqueous environments. Analyses of the theoretically obtained results along with experimental data have also been discussed.
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Affiliation(s)
- Jishnu Narayanan S J
- Department
of Chemistry, Indian Institute of Technology
Bombay, Powai, Mumbai 400076, India
| | - Divya Tripathi
- Department
of Chemistry, Indian Institute of Technology
Bombay, Powai, Mumbai 400076, India
| | - Pooja Verma
- Department
of Chemistry, Indian Institute of Technology
Bombay, Powai, Mumbai 400076, India
| | - Amitava Adhikary
- Department
of Chemistry, Oakland University, 146 Library Drive, Rochester, Michigan 48309, United States
| | - Achintya Kumar Dutta
- Department
of Chemistry, Indian Institute of Technology
Bombay, Powai, Mumbai 400076, India
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14
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WRN suppresses p53/PUMA-induced apoptosis in colorectal cancer with microsatellite instability/mismatch repair deficiency. Proc Natl Acad Sci U S A 2023; 120:e2219963120. [PMID: 36598947 PMCID: PMC9926267 DOI: 10.1073/pnas.2219963120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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15
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Mai RT, Chao CH, Chang YW, Kao YC, Cheng Y, Hsu HY, Su YY, Wang CY, Lai BY. Sumoylation participates in the regulation of YB-1-mediated mismatch repair deficiency and alkylator tolerance. Am J Cancer Res 2022; 12:5462-5483. [PMID: 36628281 PMCID: PMC9827092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2022] [Accepted: 11/27/2022] [Indexed: 01/12/2023] Open
Abstract
Numerous reports indicate that enhanced expression of Y-box binding protein-1 (YB-1) in tumor cells is strongly associated with tumorigenesis, aggressiveness, drug resistance, as well as poor prognosis in several types of cancers, and YB-1 is considered to be an oncogene. The molecular mechanism contributing to the regulation of the biological activities of YB-1 remains obscure. Sumoylation, a post-translational modification involving the covalent conjugation of small ubiquitin-like modifier (SUMO) proteins to a target protein, plays key roles in the modulation of protein functions. In this study, our results revealed that YB-1 is sumoylated and that Lys26 is a critical residue for YB-1 sumoylation. Moreover, YB-1 was found to directly interact with SUMO proteins, and disruption of the SUMO-interacting motif (SIM) of YB-1 not only interfered with this interaction but also diminished YB-1 sumoylation. The subcellular localization, protein stability, and transcriptional regulatory activity of YB-1 were not significantly affected by sumoylation. However, decreased sumoylation disrupted the interaction between YB-1 and PCNA as well as YB-1-mediated inhibition of the MutSα/PCNA interaction and MutSα mismatch binding activity, indicating a functional role of YB-1 sumoylation in inducing DNA mismatch repair (MMR) deficiency and spontaneous mutations. The MMR machinery also recognizes alkylator-modified DNA adducts to signal for cell death. We further demonstrated that YB-1 sumoylation is crucial for the inhibition of SN1-type alkylator MNNG-induced cytotoxicity, G2/M-phase arrest, apoptosis, and the MMR-dependent DNA damage response. Collectively, these results provide molecular explanations for the impact of YB-1 sumoylation on MMR deficiency and alkylator tolerance, which may provide insight for designing therapeutic strategies for malignancies and alkylator-resistant cancers associated with YB-1 overexpression.
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Affiliation(s)
- Ru-Tsun Mai
- Department of Biological Science and Technology, College of Biological Science and Technology, National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan,Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan
| | - Chi-Hong Chao
- Department of Biological Science and Technology, College of Biological Science and Technology, National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan,Institute of Molecular Medicine and Bioengineering, College of Biological Science and Technology, National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan,Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan
| | - Yao-Wen Chang
- Institute of Biochemistry and Molecular Biology, School of Life Sciences, National Yang Ming Chiao Tung UniversityTaipei 112, Taiwan
| | - Yu-Ching Kao
- Department of Biological Science and Technology, College of Biological Science and Technology, National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan,Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan
| | - Yi Cheng
- Institute of Molecular Medicine and Bioengineering, College of Biological Science and Technology, National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan,Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan
| | - Hsiang-Yu Hsu
- Institute of Molecular Medicine and Bioengineering, College of Biological Science and Technology, National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan,Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan
| | - Yi-Yuan Su
- Department of Biological Science and Technology, College of Biological Science and Technology, National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan,Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan
| | - Chen-Yun Wang
- Institute of Molecular Medicine and Bioengineering, College of Biological Science and Technology, National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan,Center for Intelligent Drug Systems and Smart Bio-devices (IDS2B), National Yang Ming Chiao Tung UniversityHsinchu 300, Taiwan
| | - Bo-Ying Lai
- Institute of Biochemistry and Molecular Biology, School of Life Sciences, National Yang Ming Chiao Tung UniversityTaipei 112, Taiwan
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16
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Yan S, Zhao J, Kemp M, Sobol RW. Editorial: Mechanistic studies of genome integrity, environmental health, and cancer etiology. Front Cell Dev Biol 2022; 10:1026326. [PMID: 36247007 PMCID: PMC9554606 DOI: 10.3389/fcell.2022.1026326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 09/07/2022] [Indexed: 01/31/2023] Open
Affiliation(s)
- Shan Yan
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC, United States,Correspondence: Shan Yan, ; Jianjun Zhao, ; Michael Kemp, ; Robert W. Sobol,
| | - Jianjun Zhao
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States,Correspondence: Shan Yan, ; Jianjun Zhao, ; Michael Kemp, ; Robert W. Sobol,
| | - Michael Kemp
- Department of Pharmacology and Toxicology, Wright State University, Dayton, OH, United States,Correspondence: Shan Yan, ; Jianjun Zhao, ; Michael Kemp, ; Robert W. Sobol,
| | - Robert W. Sobol
- Mitchell Cancer Institute and Department of Pharmacology, University of South Alabama, Mobile, AL, United States,Correspondence: Shan Yan, ; Jianjun Zhao, ; Michael Kemp, ; Robert W. Sobol,
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17
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Meas R, Nititham J, Taylor KE, Maher S, Clairmont K, Carufe KEW, Kashgarian M, Nottoli T, Cheong A, Nagel ZD, Gaffney PM, Criswell LA, Sweasy JB. A Human MSH6 Germline Variant Associated With Systemic Lupus Erythematosus Induces Lupus-like Disease in Mice. ACR Open Rheumatol 2022; 4:760-770. [PMID: 35708944 PMCID: PMC9469486 DOI: 10.1002/acr2.11471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 02/09/2022] [Accepted: 02/22/2022] [Indexed: 01/28/2023] Open
Abstract
OBJECTIVE To determine if single-nucleotide polymorphisms (SNPs) in DNA repair genes are enriched in individuals with systemic lupus erythematosus (SLE) and if they are sufficient to confer a disease phenotype in a mouse model. METHODS Human exome chip data of 2499 patients with SLE and 1230 healthy controls were analyzed to determine if variants in 10 different mismatch repair genes (MSH4, EXO1, MSH2, MSH6, MLH1, MSH3, POLH, PMS2, ML3, and APEX2) were enriched in individuals with SLE. A mouse model of the MSH6 SNP, which was found to be enriched in individuals with SLE, was created using CRISPR/Cas9 gene targeting. Wildtype mice and mice heterozygous and homozygous for the MSH6 variant were then monitored for 2 years for the development of autoimmune phenotypes, including the presence of high levels of antinuclear antibodies (ANA). Additionally, somatic hypermutation frequencies and spectra of the intronic region downstream of the VH J558-rearranged JH4 immunoglobulin gene was characterized from Peyer's patches. RESULTS Based on the human exome chip data, the MSH6 variant (rs63750897, p.Ser503Cys) is enriched among patients with SLE versus controls after we corrected for ancestry (odds ratio = 8.39, P = 0.0398). Mice homozygous for the MSH6 variant (Msh6S502C/S502C ) harbor significantly increased levels of ANA. Additionally, the Msh6S502C/S502C mice display a significant increase in the infiltration of CD68+ cells (a marker for monocytes and macrophages) into the lung alveolar space as well as apoptotic cells. Furthermore, characterization of somatic hypermutation in these mice reveals an increase in the DNA polymerase η mutational signature. CONCLUSION An MSH6 mutation that is enriched in humans diagnosed with lupus was identified. Mice harboring this Msh6 mutation develop increased autoantibodies and an inflammatory lung disease. These results suggest that the human MSH6 variant is linked to the development of SLE.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Ana Cheong
- Harvard School of Public HealthBostonMassachusettsUSA
| | | | | | - Lindsey A. Criswell
- National Institute of Arthritis and Musculoskeletal and Skin DiseasesBethesdaMarylandUSA
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18
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Castellanos M, Verhey TB, Goldstein M, Chaconas G. The Putative Endonuclease Activity of MutL Is Required for the Segmental Gene Conversion Events That Drive Antigenic Variation of the Lyme Disease Spirochete. Front Microbiol 2022; 13:888494. [PMID: 35663861 PMCID: PMC9159922 DOI: 10.3389/fmicb.2022.888494] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 04/18/2022] [Indexed: 11/30/2022] Open
Abstract
The Lyme disease spirochete Borrelia burgdorferi, encodes an elaborate antigenic variation system that promotes the ongoing variation of a major surface lipoprotein, VlsE. Changes in VlsE are continual and always one step ahead of the host acquired immune system, which requires 1–2 weeks to generate specific antibodies. By the time this happens, new VlsE variants have arisen that escape immunosurveillance, providing an avenue for persistent infection. This antigenic variation system is driven by segmental gene conversion events that transfer information from a series of silent cassettes (vls2-16) to the expression locus, vlsE. The molecular details of this process remain elusive. Recombinational switching at vlsE is RecA-independent and the only required factor identified to date is the RuvAB branch migrase. In this work we have used next generation long-read sequencing to analyze the effect of several DNA replication/recombination/repair gene disruptions on the frequency of gene conversions at vlsE and report a requirement for the mismatch repair protein MutL. Site directed mutagenesis of mutL suggests that the putative MutL endonuclease activity is required for recombinational switching at vlsE. This is the first report of an unexpected essential role for MutL in a bacterial recombination system and expands the known function of this protein as well as our knowledge of the details of the novel recombinational switching mechanism for vlsE variation.
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Affiliation(s)
- Mildred Castellanos
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada
| | - Theodore B. Verhey
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada
| | - Madeleine Goldstein
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada
| | - George Chaconas
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada
- Department of Microbiology, Immunology and Infectious Diseases, Cumming School of Medicine, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada
- *Correspondence: George Chaconas,
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19
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Genome Integrity and Neurological Disease. Int J Mol Sci 2022; 23:ijms23084142. [PMID: 35456958 PMCID: PMC9025063 DOI: 10.3390/ijms23084142] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 04/02/2022] [Accepted: 04/05/2022] [Indexed: 02/06/2023] Open
Abstract
Neurological complications directly impact the lives of hundreds of millions of people worldwide. While the precise molecular mechanisms that underlie neuronal cell loss remain under debate, evidence indicates that the accumulation of genomic DNA damage and consequent cellular responses can promote apoptosis and neurodegenerative disease. This idea is supported by the fact that individuals who harbor pathogenic mutations in DNA damage response genes experience profound neuropathological manifestations. The review article here provides a general overview of the nervous system, the threats to DNA stability, and the mechanisms that protect genomic integrity while highlighting the connections of DNA repair defects to neurological disease. The information presented should serve as a prelude to the Special Issue “Genome Stability and Neurological Disease”, where experts discuss the role of DNA repair in preserving central nervous system function in greater depth.
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20
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Cerullo F, Filbeck S, Patil PR, Hung HC, Xu H, Vornberger J, Hofer FW, Schmitt J, Kramer G, Bukau B, Hofmann K, Pfeffer S, Joazeiro CAP. Bacterial ribosome collision sensing by a MutS DNA repair ATPase paralogue. Nature 2022; 603:509-514. [PMID: 35264791 DOI: 10.1038/s41586-022-04487-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 01/28/2022] [Indexed: 12/12/2022]
Abstract
Ribosome stalling during translation is detrimental to cellular fitness, but how this is sensed and elicits recycling of ribosomal subunits and quality control of associated mRNA and incomplete nascent chains is poorly understood1,2. Here we uncover Bacillus subtilis MutS2, a member of the conserved MutS family of ATPases that function in DNA mismatch repair3, as an unexpected ribosome-binding protein with an essential function in translational quality control. Cryo-electron microscopy analysis of affinity-purified native complexes shows that MutS2 functions in sensing collisions between stalled and translating ribosomes and suggests how ribosome collisions can serve as platforms to deploy downstream processes: MutS2 has an RNA endonuclease small MutS-related (SMR) domain, as well as an ATPase/clamp domain that is properly positioned to promote ribosomal subunit dissociation, which is a requirement both for ribosome recycling and for initiation of ribosome-associated protein quality control (RQC). Accordingly, MutS2 promotes nascent chain modification with alanine-tail degrons-an early step in RQC-in an ATPase domain-dependent manner. The relevance of these observations is underscored by evidence of strong co-occurrence of MutS2 and RQC genes across bacterial phyla. Overall, the findings demonstrate a deeply conserved role for ribosome collisions in mounting a complex response to the interruption of translation within open reading frames.
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Affiliation(s)
- Federico Cerullo
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Sebastian Filbeck
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Pratik Rajendra Patil
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Hao-Chih Hung
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Haifei Xu
- Department of Molecular Medicine, Scripps Florida, Jupiter, FL, USA
| | - Julia Vornberger
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Florian W Hofer
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Jaro Schmitt
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Guenter Kramer
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Bernd Bukau
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Kay Hofmann
- Institute for Genetics, University of Cologne, Cologne, Germany
| | - Stefan Pfeffer
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany.
| | - Claudio A P Joazeiro
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Heidelberg, Germany. .,Department of Molecular Medicine, Scripps Florida, Jupiter, FL, USA.
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21
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Kligman A, Dastmalchi K, Smith S, John G, Stark RE. Building Blocks of the Protective Suberin Plant Polymer Self-Assemble into Lamellar Structures with Antibacterial Potential. ACS OMEGA 2022; 7:3978-3989. [PMID: 35155893 PMCID: PMC8829861 DOI: 10.1021/acsomega.1c04709] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Accepted: 01/06/2022] [Indexed: 05/20/2023]
Abstract
The protection of terrestrial plants from desiccation, mechanical injury, and pathogenic invasion is achieved by waxes and cutin polyesters on leaf and fruit surfaces as well as suberin polymers that are embedded in the cell walls of roots, but the physicochemical principles governing the organization of these biological composites remain incompletely understood. Despite the well-established enzymatic mediation of suberin formation in the skins of potato tubers, cork oak trees, and internal plant tissues, the additional possibility of self-assembly in this system was suggested by our serendipitous finding that solvent extracts from potato phellem tissues form suspended fibers and needles in the absence of such catalysts over a period of several weeks. In the current study, we investigated self-assembly for three-component model chemical mixtures comprised of a hydroxyfatty acid, glycerol, and either of two hydroxycinnamic acids that together typify the building blocks of potato suberin biopolymers. We demonstrate that these mixtures spontaneously form lamellar structures that are reminiscent of suberized plant tissues, incorporate all constituents into self-assemblies, can form covalently bound ester structures, and display antibacterial activity. These findings provide new perspectives on the self-association and reactivity of these classes of organic compounds, insights into agriculturally important suberin formation in food crops, and a starting point for engineering sustainable materials with antimicrobial capabilities.
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Affiliation(s)
- Arina Kligman
- Department
of Chemistry and Biochemistry, The City
College of New York, City University of New York and CUNY Institute
for Macromolecular Assemblies, 160 Convent Avenue, New
York, New York 10031, United States
- Ph.D.
Program in Chemistry, The Graduate Center
of the City University of New York, New York, New York 10016, United States
| | - Keyvan Dastmalchi
- Department
of Chemistry and Biochemistry, The City
College of New York, City University of New York and CUNY Institute
for Macromolecular Assemblies, 160 Convent Avenue, New
York, New York 10031, United States
| | - Stephan Smith
- Department
of Chemistry and Biochemistry, The City
College of New York, City University of New York and CUNY Institute
for Macromolecular Assemblies, 160 Convent Avenue, New
York, New York 10031, United States
| | - George John
- Department
of Chemistry and Biochemistry, The City
College of New York, City University of New York and CUNY Institute
for Macromolecular Assemblies, 160 Convent Avenue, New
York, New York 10031, United States
- Ph.D.
Program in Chemistry, The Graduate Center
of the City University of New York, New York, New York 10016, United States
- Ph.D.
Program in Biochemistry, The Graduate Center
of the City University of New York, New York, New York 10016, United States
| | - Ruth E. Stark
- Department
of Chemistry and Biochemistry, The City
College of New York, City University of New York and CUNY Institute
for Macromolecular Assemblies, 160 Convent Avenue, New
York, New York 10031, United States
- Ph.D.
Program in Chemistry, The Graduate Center
of the City University of New York, New York, New York 10016, United States
- Ph.D.
Program in Biochemistry, The Graduate Center
of the City University of New York, New York, New York 10016, United States
- . Phone: +1-212-650-8916. Fax: +1-212-650-6107
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22
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Takedachi A, Matsuishi E, Mizusaki S, Nagasawa T, Fujikane R, Hidaka M, Iwai S, Kuraoka I. Novel plasmids for the fluorescence-based evaluation of DNA mismatch repair in human cells. Mutat Res 2022; 824:111779. [PMID: 35472567 DOI: 10.1016/j.mrfmmm.2022.111779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 04/01/2022] [Accepted: 04/07/2022] [Indexed: 06/14/2023]
Abstract
Mismatch repair (MMR) is a highly conserved DNA repair pathway that corrects mismatched bases during DNA replication. The biological significance of MMR in human cells is underscored by the fact that dysfunction of the MMR pathway results in Lynch syndrome, which is associated with a genetic predisposition to different cancer types. We have previously established a reporter mismatch plasmid to evaluate MMR using fluorescent proteins in living cells. However, the preparation of these plasmids requires significant amounts of time and money, which reduces their broad applicability. To overcome the abovementioned limitations, we produced in this study a novel reporter plasmid, pBSII NLS-MC-EGFP-tdTomato (pBET2), that can be used in the oligo swapping method. In this method, a nicking endonuclease produces a single-stranded DNA gap on a double-stranded DNA plasmid that can be replaced by ligation with synthetic oligonucleotides. It is significantly easier and more user-friendly than previous assays, which require in vitro DNA synthesis with single-stranded plasmid DNA and purification using ultracentrifugation in cesium chloride-ethidium bromide gradients. The plasmid also contains a nicking site that allows the MMR repair machinery to efficiently distinguish the newly synthesized strand as a target for repair. In addition, a nuclear localization signal facilitates green fluorescent protein expression in the nucleus, which helps to verify the effectiveness of MMR using fluorescence microscopy. Similar to the previous reporter plasmid, this construct facilitates the assessment of MMR proficiency in human living cells via the expression of fluorescent proteins while overcoming many of the negative aspects of the previous protocol.
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Affiliation(s)
- Arato Takedachi
- Department of Chemistry, Faculty of Science, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan
| | - Erina Matsuishi
- Department of Chemistry, Faculty of Science, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan
| | - Shouji Mizusaki
- Department of Chemistry, Faculty of Science, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan
| | - Tomoki Nagasawa
- Department of Chemistry, Faculty of Science, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan
| | - Ryosuke Fujikane
- Department of Physiological Science and Molecular Biology, Fukuoka Dental College, Fukuoka 814-0193, Japan; Oral Medicine Research Center, Fukuoka Dental College, Fukuoka, 819-0193, Japan
| | - Masumi Hidaka
- Department of Physiological Science and Molecular Biology, Fukuoka Dental College, Fukuoka 814-0193, Japan; Oral Medicine Research Center, Fukuoka Dental College, Fukuoka, 819-0193, Japan
| | - Shigenori Iwai
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan
| | - Isao Kuraoka
- Department of Chemistry, Faculty of Science, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
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Inoue K, Takada S, Terakawa T. Coarse-grained molecular dynamics simulations of base-pair mismatch recognition protein MutS sliding along DNA. Biophys Physicobiol 2022; 19:1-16. [PMID: 35797408 PMCID: PMC9173861 DOI: 10.2142/biophysico.bppb-v19.0015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Accepted: 04/12/2022] [Indexed: 12/01/2022] Open
Abstract
DNA mismatches are frequently generated by various intrinsic and extrinsic factors including DNA replication errors, oxygen species, ultraviolet, and ionizing radiation. These mismatches should be corrected by the mismatches repair (MMR) pathway to maintain genome integrity. In the Escherichia coli (E. coli) MMR pathway, MutS searches and recognizes a base-pair mismatch from millions of base-pairs. Once recognized, ADP bound to MutS is exchanged with ATP, which induces a conformational change in MutS. Previous single-molecule fluorescence microscopy studies have suggested that ADP-bound MutS temporarily slides along double-stranded DNA in a rotation-coupled manner to search a base-pair mismatch and so does ATP-bound MutS in a rotation-uncoupled manner. However, the detailed structural dynamics of the sliding remains unclear. In this study, we performed coarse-grained molecular dynamics simulations of the E. coli MutS bound on DNA in three different conformations: ADP-bound (MutSADP), ATP-bound open clamp (MutSOpenATP), and ATP-bound closed clamp (MutSClosedATP) conformations. In the simulations, we observed conformation-dependent diffusion of MutS along DNA. MutSADP and MutSClosedATP diffused along DNA in a rotation-coupled manner with rare and frequent groove-crossing events, respectively. In the groove-crossing events, MutS overcame an edge of a groove and temporarily diffused in a rotation-uncoupled manner. It was also indicated that mismatch searches by MutSOpenATP is inefficient in terms of mismatch checking even though it diffuses along DNA and reaches unchecked regions more rapidly than MutSADP.
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Affiliation(s)
- Keisuke Inoue
- Department of Biophysics, Graduate School of Science, Kyoto University
| | - Shoji Takada
- Department of Biophysics, Graduate School of Science, Kyoto University
| | - Tsuyoshi Terakawa
- Department of Biophysics, Graduate School of Science, Kyoto University
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24
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Alexeeva M, Moen MN, Xu XM, Rasmussen A, Leiros I, Kirpekar F, Klungland A, Alsøe L, Nilsen H, Bjelland S. Intrinsic Strand-Incision Activity of Human UNG: Implications for Nick Generation in Immunoglobulin Gene Diversification. Front Immunol 2021; 12:762032. [PMID: 35003074 PMCID: PMC8730318 DOI: 10.3389/fimmu.2021.762032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 11/17/2021] [Indexed: 12/05/2022] Open
Abstract
Uracil arises in cellular DNA by cytosine (C) deamination and erroneous replicative incorporation of deoxyuridine monophosphate opposite adenine. The former generates C → thymine transition mutations if uracil is not removed by uracil-DNA glycosylase (UDG) and replaced by C by the base excision repair (BER) pathway. The primary human UDG is hUNG. During immunoglobulin gene diversification in activated B cells, targeted cytosine deamination by activation-induced cytidine deaminase followed by uracil excision by hUNG is important for class switch recombination (CSR) and somatic hypermutation by providing the substrate for DNA double-strand breaks and mutagenesis, respectively. However, considerable uncertainty remains regarding the mechanisms leading to DNA incision following uracil excision: based on the general BER scheme, apurinic/apyrimidinic (AP) endonuclease (APE1 and/or APE2) is believed to generate the strand break by incising the AP site generated by hUNG. We report here that hUNG may incise the DNA backbone subsequent to uracil excision resulting in a 3´-α,β-unsaturated aldehyde designated uracil-DNA incision product (UIP), and a 5´-phosphate. The formation of UIP accords with an elimination (E2) reaction where deprotonation of C2´ occurs via the formation of a C1´ enolate intermediate. UIP is removed from the 3´-end by hAPE1. This shows that the first two steps in uracil BER can be performed by hUNG, which might explain the significant residual CSR activity in cells deficient in APE1 and APE2.
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Affiliation(s)
- Marina Alexeeva
- Department of Chemistry, Bioscience and Environmental Technology, University of Stavanger, Stavanger, Norway
| | - Marivi Nabong Moen
- Department of Chemistry, Bioscience and Environmental Technology, University of Stavanger, Stavanger, Norway
- Department of Microbiology, Oslo University Hospital, Oslo, Norway
| | - Xiang Ming Xu
- Department of Chemistry, Bioscience and Environmental Technology, University of Stavanger, Stavanger, Norway
| | - Anette Rasmussen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Ingar Leiros
- Department of Chemistry, University of Tromsø-The Arctic University of Norway, Tromsø, Norway
| | - Finn Kirpekar
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
| | - Arne Klungland
- Department of Microbiology, Oslo University Hospital, Oslo, Norway
| | - Lene Alsøe
- Department of Clinical Molecular Biology, University of Oslo, Oslo, Norway
- Section of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway
| | - Hilde Nilsen
- Department of Clinical Molecular Biology, University of Oslo, Oslo, Norway
- Section of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway
- *Correspondence: Svein Bjelland, ; Hilde Nilsen,
| | - Svein Bjelland
- Department of Chemistry, Bioscience and Environmental Technology, University of Stavanger, Stavanger, Norway
- Section of Clinical Molecular Biology, Akershus University Hospital, Lørenskog, Norway
- *Correspondence: Svein Bjelland, ; Hilde Nilsen,
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25
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Evans AM, Strauss MJ, Corcos AR, Hirani Z, Ji W, Hamachi LS, Aguilar-Enriquez X, Chavez AD, Smith BJ, Dichtel WR. Two-Dimensional Polymers and Polymerizations. Chem Rev 2021; 122:442-564. [PMID: 34852192 DOI: 10.1021/acs.chemrev.0c01184] [Citation(s) in RCA: 70] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Synthetic chemists have developed robust methods to synthesize discrete molecules, linear and branched polymers, and disordered cross-linked networks. However, two-dimensional polymers (2DPs) prepared from designed monomers have been long missing from these capabilities, both as objects of chemical synthesis and in nature. Recently, new polymerization strategies and characterization methods have enabled the unambiguous realization of covalently linked macromolecular sheets. Here we review 2DPs and 2D polymerization methods. Three predominant 2D polymerization strategies have emerged to date, which produce 2DPs either as monolayers or multilayer assemblies. We discuss the fundamental understanding and scope of each of these approaches, including: the bond-forming reactions used, the synthetic diversity of 2DPs prepared, their multilayer stacking behaviors, nanoscale and mesoscale structures, and macroscale morphologies. Additionally, we describe the analytical tools currently available to characterize 2DPs in their various isolated forms. Finally, we review emergent 2DP properties and the potential applications of planar macromolecules. Throughout, we highlight achievements in 2D polymerization and identify opportunities for continued study.
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Affiliation(s)
- Austin M Evans
- Department of Chemistry, Northwestern University, 1425 Sheridan Road, Evanston, Illinois 60208, United States
| | - Michael J Strauss
- Department of Chemistry, Northwestern University, 1425 Sheridan Road, Evanston, Illinois 60208, United States
| | - Amanda R Corcos
- Department of Chemistry, Northwestern University, 1425 Sheridan Road, Evanston, Illinois 60208, United States
| | - Zoheb Hirani
- Department of Chemistry, Northwestern University, 1425 Sheridan Road, Evanston, Illinois 60208, United States
| | - Woojung Ji
- Department of Chemistry, Northwestern University, 1425 Sheridan Road, Evanston, Illinois 60208, United States
| | - Leslie S Hamachi
- Department of Chemistry, Northwestern University, 1425 Sheridan Road, Evanston, Illinois 60208, United States.,Department of Chemistry and Biochemistry, California Polytechnic State University, San Luis Obispo, California 93407, United States
| | - Xavier Aguilar-Enriquez
- Department of Chemistry, Northwestern University, 1425 Sheridan Road, Evanston, Illinois 60208, United States
| | - Anton D Chavez
- Department of Chemistry, Northwestern University, 1425 Sheridan Road, Evanston, Illinois 60208, United States
| | - Brian J Smith
- Department of Chemistry, Bucknell University,1 Dent Drive, Lewisburg, Pennsylvania 17837, United States
| | - William R Dichtel
- Department of Chemistry, Northwestern University, 1425 Sheridan Road, Evanston, Illinois 60208, United States
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26
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Yang XW, Liu J. Observing Protein One-Dimensional Sliding: Methodology and Biological Significance. Biomolecules 2021; 11:biom11111618. [PMID: 34827616 PMCID: PMC8615959 DOI: 10.3390/biom11111618] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 10/15/2021] [Accepted: 10/16/2021] [Indexed: 11/28/2022] Open
Abstract
One-dimensional (1D) sliding of DNA-binding proteins has been observed by numerous kinetic studies. It appears that many of these sliding events play important roles in a wide range of biological processes. However, one challenge is to determine the physiological relevance of these motions in the context of the protein’s biological function. Here, we discuss methods of measuring protein 1D sliding by highlighting the single-molecule approaches that are capable of visualizing particle movement in real time. We also present recent findings that show how protein sliding contributes to function.
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27
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Wilson DM, Deacon AM, Duncton MAJ, Pellicena P, Georgiadis MM, Yeh AP, Arvai AS, Moiani D, Tainer JA, Das D. Fragment- and structure-based drug discovery for developing therapeutic agents targeting the DNA Damage Response. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 163:130-142. [PMID: 33115610 PMCID: PMC8666131 DOI: 10.1016/j.pbiomolbio.2020.10.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 10/13/2020] [Accepted: 10/23/2020] [Indexed: 12/12/2022]
Abstract
Cancer will directly affect the lives of over one-third of the population. The DNA Damage Response (DDR) is an intricate system involving damage recognition, cell cycle regulation, DNA repair, and ultimately cell fate determination, playing a central role in cancer etiology and therapy. Two primary therapeutic approaches involving DDR targeting include: combinatorial treatments employing anticancer genotoxic agents; and synthetic lethality, exploiting a sporadic DDR defect as a mechanism for cancer-specific therapy. Whereas, many DDR proteins have proven "undruggable", Fragment- and Structure-Based Drug Discovery (FBDD, SBDD) have advanced therapeutic agent identification and development. FBDD has led to 4 (with ∼50 more drugs under preclinical and clinical development), while SBDD is estimated to have contributed to the development of >200, FDA-approved medicines. Protein X-ray crystallography-based fragment library screening, especially for elusive or "undruggable" targets, allows for simultaneous generation of hits plus details of protein-ligand interactions and binding sites (orthosteric or allosteric) that inform chemical tractability, downstream biology, and intellectual property. Using a novel high-throughput crystallography-based fragment library screening platform, we screened five diverse proteins, yielding hit rates of ∼2-8% and crystal structures from ∼1.8 to 3.2 Å. We consider current FBDD/SBDD methods and some exemplary results of efforts to design inhibitors against the DDR nucleases meiotic recombination 11 (MRE11, a.k.a., MRE11A), apurinic/apyrimidinic endonuclease 1 (APE1, a.k.a., APEX1), and flap endonuclease 1 (FEN1).
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Affiliation(s)
- David M Wilson
- Hasselt University, Biomedical Research Institute, Diepenbeek, Belgium; Boost Scientific, Heusden-Zolder, Belgium; XPose Therapeutics Inc., San Carlos, CA, USA
| | - Ashley M Deacon
- Accelero Biostructures Inc., San Francisco, CA, USA; XPose Therapeutics Inc., San Carlos, CA, USA
| | | | | | - Millie M Georgiadis
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA; XPose Therapeutics Inc., San Carlos, CA, USA
| | - Andrew P Yeh
- Accelero Biostructures Inc., San Francisco, CA, USA
| | - Andrew S Arvai
- Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Davide Moiani
- Department of Cancer Biology, MD Anderson Cancer Center, Houston, TX, USA; Department of Molecular and Cellular Oncology, MD Anderson Cancer Center, Houston, TX, USA
| | - John A Tainer
- Department of Cancer Biology, MD Anderson Cancer Center, Houston, TX, USA; Department of Molecular and Cellular Oncology, MD Anderson Cancer Center, Houston, TX, USA
| | - Debanu Das
- Accelero Biostructures Inc., San Francisco, CA, USA; XPose Therapeutics Inc., San Carlos, CA, USA.
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28
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Ottaiano A, Santorsola M, Caraglia M, Circelli L, Gigantino V, Botti G, Nasti G. Genetic regressive trajectories in colorectal cancer: A new hallmark of oligo-metastatic disease? Transl Oncol 2021; 14:101131. [PMID: 34034007 PMCID: PMC8144733 DOI: 10.1016/j.tranon.2021.101131] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 05/17/2021] [Accepted: 05/19/2021] [Indexed: 02/07/2023] Open
Abstract
Colorectal cancer (CRC) originates as consequence of multiple genetic alterations. Some of the involved genes have been extensively studied (APC, TP53, KRAS, SMAD4, PIK3CA, MMR genes) in highly heterogeneous and poly-metastatic cohorts. However, about 10% of metastatic CRC patients presents with an indolent oligo-metastatic disease differently from other patients with poly-metastatic and aggressive clinical course. Which are the genetic dynamics underlying the differences between oligo- and poly-metastatic CRC? The understanding of the genetic trajectories (primary→metastatic) of CRC, in patients selected to represent homogenous clinical models, is crucial to make genotype/phenotype correlations and to identify the molecular events pushing the disease towards an increasing malignant phenotype. This information is crucial to plan innovative therapeutic strategies aimed to reverse or inhibit these phenomena. In the present study, we review the genetic evolution of CRC with the intent to give a developmental perspective on the border line between oligo- and poly-metastatic diseases.
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Affiliation(s)
- Alessandro Ottaiano
- Istituto Nazionale Tumori di Napoli, IRCCS "G. Pascale", Via M. Semmola, 80131, Naples, Italy.
| | - Mariachiara Santorsola
- Istituto Nazionale Tumori di Napoli, IRCCS "G. Pascale", Via M. Semmola, 80131, Naples, Italy
| | - Michele Caraglia
- Department of Precision Medicine, University of Campania "L. Vanvitelli", Via L. De Crecchio, 7 80138, Naples, Italy; Biogem Scarl, Institute of Genetic Research, Laboratory of Precision and Molecular Oncology, 83031, Ariano Irpino, Italy
| | - Luisa Circelli
- AMES-Centro Polidiagnostico Strumentale, 80013, Casalnuovo di Napoli, Italy
| | - Valerio Gigantino
- Innovalab scarl, Molecular Biology, Centro Direzionale, isola A2, 80143, Naples, Italy
| | - Gerardo Botti
- Istituto Nazionale Tumori di Napoli, IRCCS "G. Pascale", Via M. Semmola, 80131, Naples, Italy
| | - Guglielmo Nasti
- Istituto Nazionale Tumori di Napoli, IRCCS "G. Pascale", Via M. Semmola, 80131, Naples, Italy
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29
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Thompson MK, Sobol RW, Prakash A. Exploiting DNA Endonucleases to Advance Mechanisms of DNA Repair. BIOLOGY 2021; 10:530. [PMID: 34198612 PMCID: PMC8232306 DOI: 10.3390/biology10060530] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 06/09/2021] [Accepted: 06/11/2021] [Indexed: 12/17/2022]
Abstract
The earliest methods of genome editing, such as zinc-finger nucleases (ZFN) and transcription activator-like effector nucleases (TALENs), utilize customizable DNA-binding motifs to target the genome at specific loci. While these approaches provided sequence-specific gene-editing capacity, the laborious process of designing and synthesizing recombinant nucleases to recognize a specific target sequence, combined with limited target choices and poor editing efficiency, ultimately minimized the broad utility of these systems. The discovery of clustered regularly interspaced short palindromic repeat sequences (CRISPR) in Escherichia coli dates to 1987, yet it was another 20 years before CRISPR and the CRISPR-associated (Cas) proteins were identified as part of the microbial adaptive immune system, by targeting phage DNA, to fight bacteriophage reinfection. By 2013, CRISPR/Cas9 systems had been engineered to allow gene editing in mammalian cells. The ease of design, low cytotoxicity, and increased efficiency have made CRISPR/Cas9 and its related systems the designer nucleases of choice for many. In this review, we discuss the various CRISPR systems and their broad utility in genome manipulation. We will explore how CRISPR-controlled modifications have advanced our understanding of the mechanisms of genome stability, using the modulation of DNA repair genes as examples.
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Affiliation(s)
- Marlo K. Thompson
- Mitchell Cancer Institute, University of South Alabama Health, Mobile, AL 36604, USA; (M.K.T.); (R.W.S.)
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA
| | - Robert W. Sobol
- Mitchell Cancer Institute, University of South Alabama Health, Mobile, AL 36604, USA; (M.K.T.); (R.W.S.)
- Department of Pharmacology, University of South Alabama, Mobile, AL 36688, USA
| | - Aishwarya Prakash
- Mitchell Cancer Institute, University of South Alabama Health, Mobile, AL 36604, USA; (M.K.T.); (R.W.S.)
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA
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30
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Pannafino G, Alani E. Coordinated and Independent Roles for MLH Subunits in DNA Repair. Cells 2021; 10:cells10040948. [PMID: 33923939 PMCID: PMC8074049 DOI: 10.3390/cells10040948] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Revised: 04/15/2021] [Accepted: 04/16/2021] [Indexed: 02/05/2023] Open
Abstract
The MutL family of DNA mismatch repair proteins (MMR) acts to maintain genomic integrity in somatic and meiotic cells. In baker’s yeast, the MutL homolog (MLH) MMR proteins form three heterodimeric complexes, MLH1-PMS1, MLH1-MLH2, and MLH1-MLH3. The recent discovery of human PMS2 (homolog of baker’s yeast PMS1) and MLH3 acting independently of human MLH1 in the repair of somatic double-strand breaks questions the assumption that MLH1 is an obligate subunit for MLH function. Here we provide a summary of the canonical roles for MLH factors in DNA genomic maintenance and in meiotic crossover. We then present the phenotypes of cells lacking specific MLH subunits, particularly in meiotic recombination, and based on this analysis, propose a model for an independent early role for MLH3 in meiosis to promote the accurate segregation of homologous chromosomes in the meiosis I division.
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31
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Bartke K, Garoff L, Huseby DL, Brandis G, Hughes D. Genetic Architecture and Fitness of Bacterial Interspecies Hybrids. Mol Biol Evol 2021; 38:1472-1481. [PMID: 33247724 PMCID: PMC8042766 DOI: 10.1093/molbev/msaa307] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Integration of a conjugative plasmid into a bacterial chromosome can promote the transfer of chromosomal DNA to other bacteria. Intraspecies chromosomal conjugation is believed responsible for creating the global pathogens Klebsiella pneumoniae ST258 and Escherichia coli ST1193. Interspecies conjugation is also possible but little is known about the genetic architecture or fitness of such hybrids. To study this, we generated by conjugation 14 hybrids of E. coli and Salmonella enterica. These species belong to different genera, diverged from a common ancestor >100 Ma, and share a conserved order of orthologous genes with ∼15% nucleotide divergence. Genomic analysis revealed that all but one hybrid had acquired a contiguous segment of donor E. coli DNA, replacing a homologous region of recipient Salmonella chromosome, and ranging in size from ∼100 to >4,000 kb. Recombination joints occurred in sequences with higher-than-average nucleotide identity. Most hybrid strains suffered a large reduction in growth rate, but the magnitude of this cost did not correlate with the length of foreign DNA. Compensatory evolution to ameliorate the cost of low-fitness hybrids pointed towards disruption of complex genetic networks as a cause. Most interestingly, 4 of the 14 hybrids, in which from 45% to 90% of the Salmonella chromosome was replaced with E. coli DNA, showed no significant reduction in growth fitness. These data suggest that the barriers to creating high-fitness interspecies hybrids may be significantly lower than generally appreciated with implications for the creation of novel species.
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Affiliation(s)
- Katrin Bartke
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Linnéa Garoff
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Douglas L Huseby
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Gerrit Brandis
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Diarmaid Hughes
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
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32
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Leelatian N, Hong CS, Bindra RS. The Role of Mismatch Repair in Glioblastoma Multiforme Treatment Response and Resistance. Neurosurg Clin N Am 2021; 32:171-180. [PMID: 33781500 DOI: 10.1016/j.nec.2020.12.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Mismatch repair (MMR) is a highly conserved DNA repair pathway that is critical for the maintenance of genomic integrity. This pathway targets base substitution and insertion-deletion mismatches, which primarily arise from replication errors that escape DNA polymerase proof-reading function. Here, the authors review key concepts in the molecular mechanisms of MMR in response to alkylation damage, approaches to detect MMR status in the clinic, and the clinical relevance of this pathway in glioblastoma multiforme treatment response and resistance.
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Affiliation(s)
- Nalin Leelatian
- Department of Pathology, Yale School of Medicine, 310 Cedar Street LH 108, New Haven, CT 06510, USA
| | - Christopher S Hong
- Department of Neurosurgery, Yale School of Medicine, 333 Cedar Street Tompkins 4, New Haven, CT 06510, USA
| | - Ranjit S Bindra
- Department of Therapeutic Radiology, Yale School of Medicine, 333 Cedar Street Hunter 2, New Haven, CT 06510, USA.
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Abstract
DNA mismatch repair (MMR) is a highly conserved genome stabilizing pathway that corrects DNA replication errors, limits chromosomal rearrangements, and mediates the cellular response to many types of DNA damage. Counterintuitively, MMR is also involved in the generation of mutations, as evidenced by its role in causing somatic triplet repeat expansion in Huntington’s disease (HD) and other neurodegenerative disorders. In this review, we discuss the current state of mechanistic knowledge of MMR and review the roles of key enzymes in this pathway. We also present the evidence for mutagenic function of MMR in CAG repeat expansion and consider mechanistic hypotheses that have been proposed. Understanding the role of MMR in CAG expansion may shed light on potential avenues for therapeutic intervention in HD.
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Affiliation(s)
- Ravi R Iyer
- CHDI Management/CHDI Foundation, Princeton, NJ, USA
| | - Anna Pluciennik
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA, USA
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Zell J, Rota Sperti F, Britton S, Monchaud D. DNA folds threaten genetic stability and can be leveraged for chemotherapy. RSC Chem Biol 2021; 2:47-76. [PMID: 35340894 PMCID: PMC8885165 DOI: 10.1039/d0cb00151a] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 09/20/2020] [Indexed: 12/22/2022] Open
Abstract
Damaging DNA is a current and efficient strategy to fight against cancer cell proliferation. Numerous mechanisms exist to counteract DNA damage, collectively referred to as the DNA damage response (DDR) and which are commonly dysregulated in cancer cells. Precise knowledge of these mechanisms is necessary to optimise chemotherapeutic DNA targeting. New research on DDR has uncovered a series of promising therapeutic targets, proteins and nucleic acids, with application notably via an approach referred to as combination therapy or combinatorial synthetic lethality. In this review, we summarise the cornerstone discoveries which gave way to the DNA being considered as an anticancer target, and the manipulation of DDR pathways as a valuable anticancer strategy. We describe in detail the DDR signalling and repair pathways activated in response to DNA damage. We then summarise the current understanding of non-B DNA folds, such as G-quadruplexes and DNA junctions, when they are formed and why they can offer a more specific therapeutic target compared to that of canonical B-DNA. Finally, we merge these subjects to depict the new and highly promising chemotherapeutic strategy which combines enhanced-specificity DNA damaging and DDR targeting agents. This review thus highlights how chemical biology has given rise to significant scientific advances thanks to resolutely multidisciplinary research efforts combining molecular and cell biology, chemistry and biophysics. We aim to provide the non-specialist reader a gateway into this exciting field and the specialist reader with a new perspective on the latest results achieved and strategies devised.
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Affiliation(s)
- Joanna Zell
- Institut de Chimie Moléculaire de l'Université de Bourgogne, ICMUB CNRS UMR 6302, UBFC Dijon France
| | - Francesco Rota Sperti
- Institut de Chimie Moléculaire de l'Université de Bourgogne, ICMUB CNRS UMR 6302, UBFC Dijon France
| | - Sébastien Britton
- Institut de Pharmacologie et de Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS Toulouse France
- Équipe Labellisée la Ligue Contre le Cancer 2018 Toulouse France
| | - David Monchaud
- Institut de Chimie Moléculaire de l'Université de Bourgogne, ICMUB CNRS UMR 6302, UBFC Dijon France
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35
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New developments in Huntington's disease and other triplet repeat diseases: DNA repair turns to the dark side. Neuronal Signal 2020; 4:NS20200010. [PMID: 33224521 PMCID: PMC7672267 DOI: 10.1042/ns20200010] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 10/28/2020] [Accepted: 10/30/2020] [Indexed: 02/08/2023] Open
Abstract
Huntington’s disease (HD) is a fatal, inherited neurodegenerative disease that causes neuronal death, particularly in medium spiny neurons. HD leads to serious and progressive motor, cognitive and psychiatric symptoms. Its genetic basis is an expansion of the CAG triplet repeat in the HTT gene, leading to extra glutamines in the huntingtin protein. HD is one of nine genetic diseases in this polyglutamine (polyQ) category, that also includes a number of inherited spinocerebellar ataxias (SCAs). Traditionally it has been assumed that HD age of onset and disease progression were solely the outcome of age-dependent exposure of neurons to toxic effects of the inherited mutant huntingtin protein. However, recent genome-wide association studies (GWAS) have revealed significant effects of genetic variants outside of HTT. Surprisingly, these variants turn out to be mostly in genes encoding DNA repair factors, suggesting that at least some disease modulation occurs at the level of the HTT DNA itself. These DNA repair proteins are known from model systems to promote ongoing somatic CAG repeat expansions in tissues affected by HD. Thus, for triplet repeats, some DNA repair proteins seem to abandon their normal genoprotective roles and, instead, drive expansions and accelerate disease. One attractive hypothesis—still to be proven rigorously—is that somatic HTT expansions augment the disease burden of the inherited allele. If so, therapeutic approaches that lower levels of huntingtin protein may need blending with additional therapies that reduce levels of somatic CAG repeat expansions to achieve maximal effect.
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36
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Marshall CJ, Santangelo TJ. Archaeal DNA Repair Mechanisms. Biomolecules 2020; 10:E1472. [PMID: 33113933 PMCID: PMC7690668 DOI: 10.3390/biom10111472] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 10/14/2020] [Accepted: 10/15/2020] [Indexed: 12/29/2022] Open
Abstract
Archaea often thrive in environmental extremes, enduring levels of heat, pressure, salinity, pH, and radiation that prove intolerable to most life. Many environmental extremes raise the propensity for DNA damaging events and thus, impact DNA stability, placing greater reliance on molecular mechanisms that recognize DNA damage and initiate accurate repair. Archaea can presumably prosper in harsh and DNA-damaging environments in part due to robust DNA repair pathways but surprisingly, no DNA repair pathways unique to Archaea have been described. Here, we review the most recent advances in our understanding of archaeal DNA repair. We summarize DNA damage types and their consequences, their recognition by host enzymes, and how the collective activities of many DNA repair pathways maintain archaeal genomic integrity.
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Affiliation(s)
| | - Thomas J. Santangelo
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA;
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37
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Recurrent mismatch binding by MutS mobile clamps on DNA localizes repair complexes nearby. Proc Natl Acad Sci U S A 2020; 117:17775-17784. [PMID: 32669440 DOI: 10.1073/pnas.1918517117] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
DNA mismatch repair (MMR), the guardian of the genome, commences when MutS identifies a mismatch and recruits MutL to nick the error-containing strand, allowing excision and DNA resynthesis. Dominant MMR models posit that after mismatch recognition, ATP converts MutS to a hydrolysis-independent, diffusive mobile clamp that no longer recognizes the mismatch. Little is known about the postrecognition MutS mobile clamp and its interactions with MutL. Two disparate frameworks have been proposed: One in which MutS-MutL complexes remain mobile on the DNA, and one in which MutL stops MutS movement. Here we use single-molecule FRET to follow the postrecognition states of MutS and the impact of MutL on its properties. In contrast to current thinking, we find that after the initial mobile clamp formation event, MutS undergoes frequent cycles of mismatch rebinding and mobile clamp reformation without releasing DNA. Notably, ATP hydrolysis is required to alter the conformation of MutS such that it can recognize the mismatch again instead of bypassing it; thus, ATP hydrolysis licenses the MutS mobile clamp to rebind the mismatch. Moreover, interaction with MutL can both trap MutS at the mismatch en route to mobile clamp formation and stop movement of the mobile clamp on DNA. MutS's frequent rebinding of the mismatch, which increases its residence time in the vicinity of the mismatch, coupled with MutL's ability to trap MutS, should increase the probability that MutS-MutL MMR initiation complexes localize near the mismatch.
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38
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Pećina-Šlaus N, Kafka A, Salamon I, Bukovac A. Mismatch Repair Pathway, Genome Stability and Cancer. Front Mol Biosci 2020; 7:122. [PMID: 32671096 PMCID: PMC7332687 DOI: 10.3389/fmolb.2020.00122] [Citation(s) in RCA: 122] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 05/25/2020] [Indexed: 01/02/2023] Open
Abstract
The acquisition of genomic instability is one of the key characteristics of the cancer cell, and microsatellite instability (MSI) is an important segment of this phenomenon. This review aims to describe the mismatch DNA repair (MMR) system whose deficiency is responsible for MSI and discuss the cellular roles of MMR genes. Malfunctioning of the MMR repair pathway increases the mutational burden of specific cancers and is often involved in its etiology, sometimes as an influential bystander and sometimes as the main driving force. Detecting the presence of MSI has for a long time been an important part of clinical diagnostics, but has still not achieved its full potential. The MSI blueprints of specific tumors are useful for precize grading, evaluation of cancer chance and prognosis and to help us understand how and why therapy-resistant cancers arise. Furthermore, evidence indicates that MSI is an important predictive biomarker for the application of immunotherapy.
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Affiliation(s)
- Nives Pećina-Šlaus
- Laboratory of Neurooncology, Croatian Institute for Brain Research, School of Medicine University of Zagreb, Zagreb, Croatia.,Department of Biology, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Anja Kafka
- Laboratory of Neurooncology, Croatian Institute for Brain Research, School of Medicine University of Zagreb, Zagreb, Croatia.,Department of Biology, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Iva Salamon
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, United States
| | - Anja Bukovac
- Laboratory of Neurooncology, Croatian Institute for Brain Research, School of Medicine University of Zagreb, Zagreb, Croatia.,Department of Biology, School of Medicine, University of Zagreb, Zagreb, Croatia
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39
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Dynamic human MutSα-MutLα complexes compact mismatched DNA. Proc Natl Acad Sci U S A 2020; 117:16302-16312. [PMID: 32586954 DOI: 10.1073/pnas.1918519117] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
DNA mismatch repair (MMR) corrects errors that occur during DNA replication. In humans, mutations in the proteins MutSα and MutLα that initiate MMR cause Lynch syndrome, the most common hereditary cancer. MutSα surveilles the DNA, and upon recognition of a replication error it undergoes adenosine triphosphate-dependent conformational changes and recruits MutLα. Subsequently, proliferating cell nuclear antigen (PCNA) activates MutLα to nick the error-containing strand to allow excision and resynthesis. The structure-function properties of these obligate MutSα-MutLα complexes remain mostly unexplored in higher eukaryotes, and models are predominately based on studies of prokaryotic proteins. Here, we utilize atomic force microscopy (AFM) coupled with other methods to reveal time- and concentration-dependent stoichiometries and conformations of assembling human MutSα-MutLα-DNA complexes. We find that they assemble into multimeric complexes comprising three to eight proteins around a mismatch on DNA. On the timescale of a few minutes, these complexes rearrange, folding and compacting the DNA. These observations contrast with dominant models of MMR initiation that envision diffusive MutS-MutL complexes that move away from the mismatch. Our results suggest MutSα localizes MutLα near the mismatch and promotes DNA configurations that could enhance MMR efficiency by facilitating MutLα nicking the DNA at multiple sites around the mismatch. In addition, such complexes may also protect the mismatch region from nucleosome reassembly until repair occurs, and they could potentially remodel adjacent nucleosomes.
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40
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Probing the DNA-binding center of the MutL protein from the Escherichia coli mismatch repair system via crosslinking and Förster resonance energy transfer. Biochimie 2020; 171-172:43-54. [PMID: 32061805 DOI: 10.1016/j.biochi.2020.02.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 02/11/2020] [Indexed: 11/23/2022]
Abstract
As no crystal structure of full-size MutL bound to DNA has been obtained up to date, in the present work we used crosslinking and Förster resonance energy transfer (FRET) assays for probing the putative DNA-binding center of MutL from Escherichia coli. Several single-cysteine MutL variants (scMutL) were used for site-specific crosslinking or fluorophore modification. The crosslinking efficiency between scMutL proteins and mismatched DNA modified with thiol-reactive probes correlated with the distances from the Cys residues to the DNA calculated from a model of MutS-MutL-DNA complex. FRET-based investigation of DNA binding with different scMutL variants clearly showed that the highest signals were detected for the variants MutL(T218C) and MutL(A251C) indicating closeness of the positions 218 and 251 to DNA in the MutL-DNA complex. Indeed, the Cys218 and Cys251 of scMutL were crosslinked to the reactive DNA with the highest yield demonstrating their proximity to DNA in the MutL-DNA complex. The presence of MutS increased the yield of conjugate formation between the MutL variants and the modified DNA due to tighter MutL-DNA interactions caused by MutS binding to MutL.
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41
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Chirinos-Arias MC, Spampinato CP. Growth and development of AtMSH7 mutants in Arabidopsis thaliana. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2020; 146:329-336. [PMID: 31785519 DOI: 10.1016/j.plaphy.2019.11.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 11/18/2019] [Accepted: 11/22/2019] [Indexed: 06/10/2023]
Abstract
DNA mismatch repair (MMR) is a highly conserved biological pathway that improves the fidelity of DNA replication and recombination. MMR is initiated when MutS proteins recognize mismatches and small loops of unpaired nucleotides. Arabidopsis thaliana and other plants encode MutS protein homologs (MSH) conserved among other eukaryotic organisms, but also encode an extra MSH polypeptide (MSH7). In order to better understand the role of MSH7 in vivo, a full set of phenotypic parameters that covered the development of the plant from seed imbibition to flowering and seed maturation was analyzed in A. thaliana harboring two different msh7 alleles. Plants deficient in MSH7 show statistically significant faster germination rates, longer primary roots during the juvenile vegetative phase, and higher cauline leaf and axillary and lateral inflorescence numbers compared with wild type. We also quantified number, length and area of siliques and seed number per silique. Disruption of MSH7 resulted in a higher number of smaller siliques than wild type. There were no differences in seed number per silique between genotypes. These findings suggest that mutant plant growth appears to be caused by an impaired cell cycle checkpoint that allows cell division without adequate DNA repair. This increase in proliferation activity demonstrates a functional and temporal link between DNA repair and cell cycle regulation.
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Affiliation(s)
- Michelle C Chirinos-Arias
- Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000, Rosario, Argentina
| | - Claudia P Spampinato
- Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000, Rosario, Argentina.
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42
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LeBlanc SJ, Gauer JW, Hao P, Case BC, Hingorani MM, Weninger KR, Erie DA. Coordinated protein and DNA conformational changes govern mismatch repair initiation by MutS. Nucleic Acids Res 2019; 46:10782-10795. [PMID: 30272207 PMCID: PMC6237781 DOI: 10.1093/nar/gky865] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 09/26/2018] [Indexed: 12/13/2022] Open
Abstract
MutS homologs identify base-pairing errors made in DNA during replication and initiate their repair. In the presence of adenosine triphosphate, MutS induces DNA bending upon mismatch recognition and subsequently undergoes conformational transitions that promote its interaction with MutL to signal repair. In the absence of MutL, these transitions lead to formation of a MutS mobile clamp that can move along the DNA. Previous single-molecule FRET (smFRET) studies characterized the dynamics of MutS DNA-binding domains during these transitions. Here, we use protein–DNA and DNA–DNA smFRET to monitor DNA conformational changes, and we use kinetic analyses to correlate DNA and protein conformational changes to one another and to the steps on the pathway to mobile clamp formation. The results reveal multiple sequential structural changes in both MutS and DNA, and they suggest that DNA dynamics play a critical role in the formation of the MutS mobile clamp. Taking these findings together with data from our previous studies, we propose a unified model of coordinated MutS and DNA conformational changes wherein initiation of mismatch repair is governed by a balance of DNA bending/unbending energetics and MutS conformational changes coupled to its nucleotide binding properties.
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Affiliation(s)
- Sharonda J LeBlanc
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.,Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
| | - Jacob W Gauer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Pengyu Hao
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
| | - Brandon C Case
- Molecular Biology and Biochemistry Department, Wesleyan University, Middletown, CT 06459, USA
| | - Manju M Hingorani
- Molecular Biology and Biochemistry Department, Wesleyan University, Middletown, CT 06459, USA
| | - Keith R Weninger
- Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
| | - Dorothy A Erie
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.,Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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43
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Harmsen T, Klaasen S, van de Vrugt H, Te Riele H. DNA mismatch repair and oligonucleotide end-protection promote base-pair substitution distal from a CRISPR/Cas9-induced DNA break. Nucleic Acids Res 2019; 46:2945-2955. [PMID: 29447381 PMCID: PMC5888797 DOI: 10.1093/nar/gky076] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 01/25/2018] [Indexed: 12/14/2022] Open
Abstract
Single-stranded oligodeoxyribonucleotide (ssODN)-mediated repair of CRISPR/Cas9-induced DNA double-strand breaks (DSB) can effectively be used to introduce small genomic alterations in a defined locus. Here, we reveal DNA mismatch repair (MMR) activity is crucial for efficient nucleotide substitution distal from the Cas9-induced DNA break when the substitution is instructed by the 3' half of the ssODN. Furthermore, protecting the ssODN 3' end with phosphorothioate linkages enhances MMR-dependent gene editing events. Our findings can be exploited to optimize efficiencies of nucleotide substitutions distal from the DSB and imply that oligonucleotide-mediated gene editing is effectuated by templated break repair.
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Affiliation(s)
- Tim Harmsen
- Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Sjoerd Klaasen
- Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Henri van de Vrugt
- Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.,Department of Clinical Genetics, VU University Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands
| | - Hein Te Riele
- Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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44
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Tamura K, Kaneda M, Futagawa M, Takeshita M, Kim S, Nakama M, Kawashita N, Tatsumi-Miyajima J. Genetic and genomic basis of the mismatch repair system involved in Lynch syndrome. Int J Clin Oncol 2019; 24:999-1011. [PMID: 31273487 DOI: 10.1007/s10147-019-01494-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 06/17/2019] [Indexed: 12/11/2022]
Abstract
Lynch syndrome is a cancer-predisposing syndrome inherited in an autosomal-dominant manner, wherein colon cancer and endometrial cancer develop frequently in the family, it results from a loss-of-function mutation in one of four different genes (MLH1, MSH2, MSH6, and PMS2) encoding mismatch repair proteins. Being located immediately upstream of the MSH2 gene, EPCAM abnormalities can affect MSH2 and cause Lynch syndrome. Mismatch repair proteins are involved in repairing of incorrect pairing (point mutations and deletion/insertion of simple repetitive sequences, so-called microsatellites) that can arise during DNA replication. MSH2 forms heterodimers with MSH6 or MSH3 (MutSα, MutSβ, respectively) and is involved in mismatch-pair recognition and initiation of repair. MLH1 forms a complex with PMS2, and functions as an endonuclease. If the mismatch repair system is thoroughly working, genome integrity is maintained completely. Lynch syndrome is a state of mismatch repair deficiency due to a monoallelic abnormality of any mismatch repair genes. The phenotype indicating the mismatch repair deficiency can be frequently shown as a microsatellite instability in tumors. Children with germline biallelic mismatch repair gene abnormalities were reported to develop conditions such as gastrointestinal polyposis, colorectal cancer, brain cancer, leukemia, etc., and so on, demonstrating the need to respond with new concepts in genetic counseling. In promoting cancer genome medicine in a new era, such as by utilizing immune checkpoints, it is important to understand the genetic and genomic molecular background, including the status of mismatch repair deficiency.
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Affiliation(s)
- Kazuo Tamura
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan.
| | - Motohide Kaneda
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan
| | - Mashu Futagawa
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan
| | - Miho Takeshita
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan
| | - Sanghyuk Kim
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan
| | - Mina Nakama
- Division of Clinical Genetics, Gifu University Hospital, Gifu, Japan
| | - Norihito Kawashita
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan
| | - Junko Tatsumi-Miyajima
- Division of Medical Genetics, Master of Science, Graduate School of Science and Engineering Research, Kindai University, Higashiosaka, Japan
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45
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DNA Rereplication Is Susceptible to Nucleotide-Level Mutagenesis. Genetics 2019; 212:445-460. [PMID: 31028114 PMCID: PMC6553831 DOI: 10.1534/genetics.119.302194] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 04/15/2019] [Indexed: 12/12/2022] Open
Abstract
The initiation of eukaryotic DNA replication at replication origins is tightly regulated to prevent re-initiation and re-replication within each cell cycle. This regulation is critical for genome stability as re-replication is an extremely potent inducer... The sources of genome instability, a hallmark of cancer, remain incompletely understood. One potential source is DNA rereplication, which arises when the mechanisms that prevent the reinitiation of replication origins within a single cell cycle are compromised. Using the budding yeast Saccharomyces cerevisiae, we previously showed that DNA rereplication is extremely potent at inducing gross chromosomal alterations and that this arises in part because of the susceptibility of rereplication forks to break. Here, we examine the ability of DNA rereplication to induce nucleotide-level mutations. During normal replication these mutations are restricted by three overlapping error-avoidance mechanisms: the nucleotide selectivity of replicative polymerases, their proofreading activity, and mismatch repair. Using lys2InsEA14, a frameshift reporter that is poorly proofread, we show that rereplication induces up to a 30× higher rate of frameshift mutations and that this mutagenesis is due to passage of the rereplication fork, not secondary to rereplication fork breakage. Rereplication can also induce comparable rates of frameshift and base-substitution mutations in a more general mutagenesis reporter CAN1, when the proofreading activity of DNA polymerase ε is inactivated. Finally, we show that the rereplication-induced mutagenesis of both lys2InsEA14 and CAN1 disappears in the absence of mismatch repair. These results suggest that mismatch repair is attenuated during rereplication, although at most sequences DNA polymerase proofreading provides enough error correction to mitigate the mutagenic consequences. Thus, rereplication can facilitate nucleotide-level mutagenesis in addition to inducing gross chromosomal alterations, broadening its potential role in genome instability.
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46
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In vivo demonstration of enhanced binding between β-clamp and DnaE of pol III bearing consensus i-CBM. Genes Genomics 2019; 41:613-619. [PMID: 30929144 DOI: 10.1007/s13258-019-00796-9] [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: 10/04/2018] [Accepted: 02/15/2019] [Indexed: 10/27/2022]
Abstract
BACKGROUND Among several key protein-protein and protein-DNA interactions within the replisome, the interaction between β-clamp and the DNA polymerase (Pol) III is of crucial importance. This interaction is mediated by a five or six-residue conserved sequence of the DnaE subunit of Pol III, referred to as the Clamp Binding Motif (CBM). In E. coli, DnaE contains two CBMs designated as e-CBM and i-CBM. A consensus sequence (QL[S/D]LF) for the CBMs has previously been proposed and studies involving mutagenesis of both the CBMs have evaluated their protein-binding properties. Surface Plasmon Resonance has been used to show that replacing i-CBM in DnaE with the consensus sequence enhances its binding to β-clamp 120-fold. OBJECTIVE The current study was aimed to evaluate in vivo interaction between DnaE bearing the consensus i-CBM and β-clamp. METHOD The C-terminal 405 residues of DnaE, bearing either the consensus i-CBM or the WT i-CBM, with β-clamp were co-expressed in E. coli followed by co-purification of the protein complexes. The interaction was assessed by the ability of the co-expressed proteins to form stable complexes during both affinity and gel filtration chromatography. RESULT The interaction of β-clamp with DnaEΔ755M containing the consensus i-CBM was found to be more stable than with WT DnaEΔ755, consistent with the in vitro data previously reported. CONCLUSION The presence of the pieces of sheared DNA generated during sonication promote the interaction of DnaEΔ755M with β-clamp by binding the OB-fold of DnaEΔ755M and β-clamp and serves as a bridge between them.
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47
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Klein CB. Emerging confluences of epigenetics and DNA repair in cancer and disease. MUTATION RESEARCH. REVIEWS IN MUTATION RESEARCH 2019; 780:11-14. [PMID: 31395354 DOI: 10.1016/j.mrrev.2019.108282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Affiliation(s)
- Catherine B Klein
- Department of Environmental Medicine, NYU School of Medicine, 341 East 25 Street, New York, NY, 10010, United States.
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48
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Muenter MM, Aiken A, Akanji JO, Baig S, Bellou S, Carlson A, Conway C, Cowell CM, DeLateur NA, Hester A, Joshi C, Kramer C, Leifer BS, Nash E, Qi MH, Travers M, Wong KC, Hu M, Gou N, Giese RW, Gu AZ, Beuning PJ. The response of Escherichia coli to the alkylating agents chloroacetaldehyde and styrene oxide. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2019; 840:1-10. [PMID: 30857727 DOI: 10.1016/j.mrgentox.2019.02.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2018] [Revised: 02/06/2019] [Accepted: 02/06/2019] [Indexed: 10/27/2022]
Abstract
DNA damage is ubiquitous and can arise from endogenous or exogenous sources. DNA-damaging alkylating agents are present in environmental toxicants as well as in cancer chemotherapy drugs and are a constant threat, which can lead to mutations or cell death. All organisms have multiple DNA repair and DNA damage tolerance pathways to resist the potentially negative effects of exposure to alkylating agents. In bacteria, many of the genes in these pathways are regulated as part of the SOS reponse or the adaptive response. In this work, we probed the cellular responses to the alkylating agents chloroacetaldehyde (CAA), which is a metabolite of 1,2-dichloroethane used to produce polyvinyl chloride, and styrene oxide (SO), a major metabolite of styrene used in the production of polystyrene and other polymers. Vinyl chloride and styrene are produced on an industrial scale of billions of kilograms annually and thus have a high potential for environmental exposure. To identify stress response genes in E. coli that are responsible for tolerance to the reactive metabolites CAA and SO, we used libraries of transcriptional reporters and gene deletion strains. In response to both alkylating agents, genes associated with several different stress pathways were upregulated, including protein, membrane, and oxidative stress, as well as DNA damage. E. coli strains lacking genes involved in base excision repair and nucleotide excision repair were sensitive to SO, whereas strains lacking recA and the SOS gene ybfE were sensitive to both alkylating agents tested. This work indicates the varied systems involved in cellular responses to alkylating agents, and highlights the specific DNA repair genes involved in the responses.
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Affiliation(s)
- Mark M Muenter
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Ariel Aiken
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Jadesola O Akanji
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Samir Baig
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Sirine Bellou
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Alyssa Carlson
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Charles Conway
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Courtney M Cowell
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Nicholas A DeLateur
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Alexis Hester
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Christopher Joshi
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Caitlin Kramer
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Becky S Leifer
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Emma Nash
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Macee H Qi
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Meghan Travers
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Kelly C Wong
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA
| | - Man Hu
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA, 02115 USA
| | - Na Gou
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA, 02115 USA; School of Civil and Environmental Engineering, Cornell University, Ithaca, NY, 14850, USA
| | - Roger W Giese
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA, 02115 USA
| | - April Z Gu
- Department of Civil and Environmental Engineering, Northeastern University, Boston, MA, 02115 USA; School of Civil and Environmental Engineering, Cornell University, Ithaca, NY, 14850, USA
| | - Penny J Beuning
- Department of Chemistry & Chemical Biology, Northeastern University, Boston, MA, 02115 USA.
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49
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D'Arcy BM, Blount J, Prakash A. Biochemical and structural characterization of two variants of uncertain significance in the PMS2 gene. Hum Mutat 2019; 40:458-471. [PMID: 30653781 DOI: 10.1002/humu.23708] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Revised: 12/28/2018] [Accepted: 01/14/2019] [Indexed: 12/16/2022]
Abstract
Lynch syndrome (LS) is an autosomal dominant inherited disorder that is associated with an increased predisposition to certain cancers caused by loss-of-function mutations in one of four DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6, or PMS2). The diagnosis of LS is often challenged by the identification of missense mutations where the functional effects are not known. These are termed variants of uncertain significance (VUSs) and account for 20%-30% of noncoding and missense mutations. VUSs cause ambiguity during clinical diagnosis and hinder implementation of appropriate medical management. In the current study, we focus on the functional and biological consequences of two nonsynonymous VUSs in PMS2. These variants, c.620G>A and c.123_131delGTTAGTAGA, result in the alteration of glycine 207 to glutamate (p.Gly207Glu) and the deletion of amino acid residues 42-44 (p.Leu42_Glu44del), respectively. While the PMS2 p.Gly207Glu variant retains in vitro MMR and ATPase activities, PMS2 p.Leu42_Glu44del appears to lack such capabilities. Structural and biophysical characterization using circular dichroism, small-angle X-ray scattering, and X-ray crystallography of the N-terminal domain of the PMS2 variants indicate that the p.Gly207Glu variant is properly folded similar to the wild-type enzyme, whereas p.Leu42_Glu44del is disordered and prone to aggregation.
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Affiliation(s)
- Brandon M D'Arcy
- Mitchell Cancer Institute, The University of South Alabama, Mobile, Alabama
| | - Jessa Blount
- Mitchell Cancer Institute, The University of South Alabama, Mobile, Alabama
| | - Aishwarya Prakash
- Mitchell Cancer Institute, The University of South Alabama, Mobile, Alabama
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50
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Abstract
The mitochondrial genome encodes proteins essential for the oxidative phosphorylation and, consequently, for proper mitochondrial function. Its localization and, possibly, structural organization contribute to higher DNA damage accumulation, when compared to the nuclear genome. In addition, the mitochondrial genome mutates at rates several times higher than the nuclear, although the causal relationship between these events are not clearly established. Maintaining mitochondrial DNA stability is critical for cellular function and organismal fitness, and several pathways contribute to that, including damage tolerance and bypass, degradation of damaged genomes and DNA repair. Despite initial evidence suggesting that mitochondria lack DNA repair activities, most DNA repair pathways have been at least partially characterized in mitochondria from several model organisms, including humans. In this chapter, we review what is currently known about how the main DNA repair pathways operate in mitochondria and contribute to mitochondrial DNA stability, with focus on the enzymology of mitochondrial DNA repair.
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Affiliation(s)
- Rebeca R Alencar
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
| | - Caio M P F Batalha
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
| | - Thiago S Freire
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
| | - Nadja C de Souza-Pinto
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
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