1
|
Boyd BM, James I, Johnson KP, Weiss RB, Bush SE, Clayton DH, Dale C. Stochasticity, determinism, and contingency shape genome evolution of endosymbiotic bacteria. Nat Commun 2024; 15:4571. [PMID: 38811551 PMCID: PMC11137140 DOI: 10.1038/s41467-024-48784-2] [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: 07/06/2023] [Accepted: 05/10/2024] [Indexed: 05/31/2024] Open
Abstract
Evolution results from the interaction of stochastic and deterministic processes that create a web of historical contingency, shaping gene content and organismal function. To understand the scope of this interaction, we examine the relative contributions of stochasticity, determinism, and contingency in shaping gene inactivation in 34 lineages of endosymbiotic bacteria, Sodalis, found in parasitic lice, Columbicola, that are independently undergoing genome degeneration. Here we show that the process of genome degeneration in this system is largely deterministic: genes involved in amino acid biosynthesis are lost while those involved in providing B-vitamins to the host are retained. In contrast, many genes encoding redundant functions, including components of the respiratory chain and DNA repair pathways, are subject to stochastic loss, yielding historical contingencies that constrain subsequent losses. Thus, while selection results in functional convergence between symbiont lineages, stochastic mutations initiate distinct evolutionary trajectories, generating diverse gene inventories that lack the functional redundancy typically found in free-living relatives.
Collapse
Affiliation(s)
- Bret M Boyd
- Center for Biological Data Science, Virginia Commonwealth University, Richmond, VA, US.
| | - Ian James
- School of Biological Sciences, University of Utah, Salt Lake City, UT, US
| | - Kevin P Johnson
- Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, IL, US
| | - Robert B Weiss
- Department of Human Genetics, University of Utah, Salt Lake City, UT, US
| | - Sarah E Bush
- School of Biological Sciences, University of Utah, Salt Lake City, UT, US
| | - Dale H Clayton
- School of Biological Sciences, University of Utah, Salt Lake City, UT, US
| | - Colin Dale
- School of Biological Sciences, University of Utah, Salt Lake City, UT, US
| |
Collapse
|
2
|
Clark BS, Silvernail I, Gordon K, Castaneda JF, Morgan AN, Rolband LA, LeBlanc SJ. A practical guide to time-resolved fluorescence microscopy and spectroscopy. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.25.577300. [PMID: 38586000 PMCID: PMC10996486 DOI: 10.1101/2024.01.25.577300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
Time-correlated single photon counting (TCSPC) coupled with confocal microscopy is a versatile biophysical tool that enables real-time monitoring of biomolecular dynamics across many timescales. With TCSPC, Fluorescence correlation spectroscopy (FCS) and pulsed interleaved excitation-Förster resonance energy transfer (PIE-FRET) are collected simultaneously on diffusing molecules to extract diffusion characteristics and proximity information. This article is a guide to calibrating FCS and PIE-FRET measurements with several biological samples including liposomes, streptavidin-coated quantum dots, proteins, and nucleic acids for reliable determination of diffusion coefficients and FRET efficiency. The FRET efficiency results are also compared to surface-attached single molecules using fluorescence lifetime imaging microscopy (FLIM-FRET). Combining the methods is a powerful approach to revealing mechanistic details of biological processes and pathways.
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
Britton BM, London JA, Martin-Lopez J, Jones ND, Liu J, Lee JB, Fishel R. Exploiting the distinctive properties of the bacterial and human MutS homolog sliding clamps on mismatched DNA. J Biol Chem 2022; 298:102505. [PMID: 36126773 PMCID: PMC9597889 DOI: 10.1016/j.jbc.2022.102505] [Citation(s) in RCA: 2] [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] [Received: 10/22/2021] [Revised: 09/13/2022] [Accepted: 09/15/2022] [Indexed: 12/30/2022] Open
Abstract
MutS homologs (MSHs) are highly conserved core components of DNA mismatch repair. Mismatch recognition provokes ATP-binding by MSH proteins that drives a conformational transition from a short-lived lesion-searching clamp to an extremely stable sliding clamp on the DNA. Here, we have expanded on previous bulk biochemical studies to examine the stability, lifetime, and kinetics of bacterial and human MSH sliding clamps on mismatched DNA using surface plasmon resonance and single-molecule analysis of fluorescently labeled proteins. We found that ATP-bound MSH complexes bound to blocked-end or very long mismatched DNAs were extremely stable over a range of ionic conditions. These observations underpinned the development of a high-throughput Förster resonance energy transfer system that specifically detects the formation of MSH sliding clamps on mismatched DNA. The Förster resonance energy transfer system is capable of distinguishing between HsMSH2-HsMSH3 and HsMSH2-HsMSH6 and appears suitable for chemical inhibitor screens. Taken together, our results provide additional insight into MSH sliding clamps as well as methods to distinguish their functions in mismatch repair.
Collapse
Affiliation(s)
- Brooke M Britton
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - James A London
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Juana Martin-Lopez
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Nathan D Jones
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Jiaquan Liu
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA
| | - Jong-Bong Lee
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, Korea; Interdisciplinary Bioscience and Bioengineering, POSTECH, Pohang, Korea
| | - Richard Fishel
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, Ohio, USA.
| |
Collapse
|
5
|
Yang XW, Han XP, Han C, London J, Fishel R, Liu J. MutS functions as a clamp loader by positioning MutL on the DNA during mismatch repair. Nat Commun 2022; 13:5808. [PMID: 36192430 PMCID: PMC9530208 DOI: 10.1038/s41467-022-33479-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 09/20/2022] [Indexed: 11/20/2022] Open
Abstract
Highly conserved MutS and MutL homologs operate as protein dimers in mismatch repair (MMR). MutS recognizes mismatched nucleotides forming ATP-bound sliding clamps, which subsequently load MutL sliding clamps that coordinate MMR excision. Several MMR models envision static MutS-MutL complexes bound to mismatched DNA via a positively charged cleft (PCC) located on the MutL N-terminal domains (NTD). We show MutL-DNA binding is undetectable in physiological conditions. Instead, MutS sliding clamps exploit the PCC to position a MutL NTD on the DNA backbone, likely enabling diffusion-mediated wrapping of the remaining MutL domains around the DNA. The resulting MutL sliding clamp enhances MutH endonuclease and UvrD helicase activities on the DNA, which also engage the PCC during strand-specific incision/excision. These MutS clamp-loader progressions are significantly different from the replication clamp-loaders that attach the polymerase processivity factors β-clamp/PCNA to DNA, highlighting the breadth of mechanisms for stably linking crucial genome maintenance proteins onto DNA.
Collapse
Affiliation(s)
- Xiao-Wen Yang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai, 200031, China
| | - Xiao-Peng Han
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai, 200031, China
| | - Chong Han
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai, 200031, China
| | - James London
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Richard Fishel
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA.
- The Molecular Carcinogenesis and Chemoprevention Program, The James Comprehensive Cancer Center, Columbus, OH, 43210, USA.
| | - Jiaquan Liu
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai, 200031, China.
| |
Collapse
|
6
|
Hasan A, Rizvi SF, Parveen S, Mir SS. Molecular chaperones in DNA repair mechanisms: Role in genomic instability and proteostasis in cancer. Life Sci 2022; 306:120852. [DOI: 10.1016/j.lfs.2022.120852] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 07/14/2022] [Accepted: 07/27/2022] [Indexed: 01/09/2023]
|
7
|
CNOT6: A Novel Regulator of DNA Mismatch Repair. Cells 2022; 11:cells11030521. [PMID: 35159331 PMCID: PMC8833972 DOI: 10.3390/cells11030521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 01/29/2022] [Accepted: 01/31/2022] [Indexed: 11/16/2022] Open
Abstract
DNA mismatch repair (MMR) is a highly conserved pathway that corrects both base–base mispairs and insertion-deletion loops (IDLs) generated during DNA replication. Defects in MMR have been linked to carcinogenesis and drug resistance. However, the regulation of MMR is poorly understood. Interestingly, CNOT6 is one of four deadenylase subunits in the conserved CCR4-NOT complex and it targets poly(A) tails of mRNAs for degradation. CNOT6 is overexpressed in acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML) and androgen-independent prostate cancer cells, which suggests that an altered expression of CNOT6 may play a role in tumorigenesis. Here, we report that a depletion of CNOT6 sensitizes human U2OS cells to N-methyl-N′nitro-N-nitrosoguanidine (MNNG) and leads to enhanced apoptosis. We also demonstrate that the depletion of CNOT6 upregulates MMR and decreases the mutation frequency in MMR-proficient cells. Furthermore, the depletion of CNOT6 increases the stability of mRNA transcripts from MMR genes, leading to the increased expression of MMR proteins. Our work provides insight into a novel CNOT6-dependent mechanism for regulating MMR.
Collapse
|
8
|
Charbonnier JB. Tandem regulation of MutS activity by ATP and DNA during MMR initiation. Nat Struct Mol Biol 2022; 29:5-7. [PMID: 35027743 DOI: 10.1038/s41594-021-00713-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Jean Baptiste Charbonnier
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, Gif-sur-Yvette, France.
| |
Collapse
|
9
|
Leitner M, Bishop C, Asgari S. Transcriptional Response of Wolbachia to Dengue Virus Infection in Cells of the Mosquito Aedes aegypti. mSphere 2021; 6:e0043321. [PMID: 34190587 PMCID: PMC8265661 DOI: 10.1128/msphere.00433-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 06/07/2021] [Indexed: 11/20/2022] Open
Abstract
Aedes aegypti transmits one of the most significant mosquito-borne viruses, dengue virus (DENV). The absence of effective vaccines and clinical treatments and the emergence of insecticide resistance in A. aegypti necessitate novel vector control strategies. A new approach uses the endosymbiotic bacterium Wolbachia pipientis to reduce the spread of arboviruses. However, the Wolbachia-mediated antiviral mechanism is not well understood. To shed light on this mechanism, we investigated an unexplored aspect of Wolbachia-virus-mosquito interaction. We used RNA sequencing to examine the transcriptional response of Wolbachia to DENV infection in A. aegypti Aag2 cells transinfected with the wAlbB strain of Wolbachia. Our results suggest that genes encoding an endoribonuclease (RNase HI), a regulator of sigma 70-dependent gene transcription (6S RNA), essential cellular, transmembrane, and stress response functions and primary type I and IV secretion systems were upregulated, while a number of transport and binding proteins of Wolbachia, ribosome structure, and elongation factor-associated genes were downregulated due to DENV infection. Furthermore, bacterial retrotransposon, transposable, and phage-related elements were found among the up- and downregulated genes. We show that Wolbachia elicits a transcriptional response to virus infection and identify differentially expressed Wolbachia genes mostly at the early stages of virus infection. These findings highlight Wolbachia's ability to alter its gene expression in response to DENV infection of the host cell. IMPORTANCE Aedes aegypti is a vector of several pathogenic viruses, including dengue, Zika, chikungunya, and yellow fever viruses, which are of importance to human health. Wolbachia is an endosymbiotic bacterium currently used in transinfected mosquitoes to suppress replication and transmission of dengue viruses. However, the mechanism of Wolbachia-mediated virus inhibition is not fully understood. While several studies have shown mosquitoes' transcriptional responses to dengue virus infection, none have investigated these responses in Wolbachia, which may provide clues to the inhibition mechanism. Our results suggest changes in the expression of a number of functionally important Wolbachia genes upon dengue virus infection, including those involved in stress responses, providing insights into the endosymbiont's reaction to virus infection.
Collapse
Affiliation(s)
- Michael Leitner
- Australian Infectious Disease Research Centre, School of Biological Sciences, The University of Queensland, Brisbane, Australia
| | - Cameron Bishop
- Australian Infectious Disease Research Centre, School of Biological Sciences, The University of Queensland, Brisbane, Australia
| | - Sassan Asgari
- Australian Infectious Disease Research Centre, School of Biological Sciences, The University of Queensland, Brisbane, Australia
| |
Collapse
|
10
|
Strand discrimination in DNA mismatch repair. DNA Repair (Amst) 2021; 105:103161. [PMID: 34171627 DOI: 10.1016/j.dnarep.2021.103161] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 06/15/2021] [Accepted: 06/16/2021] [Indexed: 11/24/2022]
Abstract
DNA mismatch repair (MMR) corrects non-Watson-Crick basepairs generated by replication errors, recombination intermediates, and some forms of chemical damage to DNA. In MutS and MutL homolog-dependent MMR, damaged bases do not identify the error-containing daughter strand that must be excised and resynthesized. In organisms like Escherichia coli that use methyl-directed MMR, transient undermethylation identifies the daughter strand. For other organisms, growing in vitro and in vivo evidence suggest that strand discrimination is mediated by DNA replication-associated daughter strand nicks that direct asymmetric loading of the replicative clamp (the β-clamp in bacteria and the proliferating cell nuclear antigen, PCNA, in eukaryotes). Structural modeling suggests that replicative clamps mediate strand specificity either through the ability of MutL homologs to recognize the fixed orientation of the daughter strand relative to one face of the replicative clamps or through parental strand-specific diffusion of replicative clamps on DNA, which places the daughter strand in the MutL homolog endonuclease active site. Finally, identification of bacteria that appear to lack strand discrimination mediated by a replicative clamp and a pre-existing nick suggest that other strand discrimination mechanisms exist or that these organisms perform MMR by generating a double-stranded DNA break intermediate, which may be analogous to NucS-mediated MMR.
Collapse
|
11
|
Elez M. Mismatch Repair: From Preserving Genome Stability to Enabling Mutation Studies in Real-Time Single Cells. Cells 2021; 10:cells10061535. [PMID: 34207040 PMCID: PMC8235422 DOI: 10.3390/cells10061535] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 06/11/2021] [Accepted: 06/15/2021] [Indexed: 12/18/2022] Open
Abstract
Mismatch Repair (MMR) is an important and conserved keeper of the maintenance of genetic information. Miroslav Radman's contributions to the field of MMR are multiple and tremendous. One of the most notable was to provide, along with Bob Wagner and Matthew Meselson, the first direct evidence for the existence of the methyl-directed MMR. The purpose of this review is to outline several aspects and biological implications of MMR that his work has helped unveil, including the role of MMR during replication and recombination editing, and the current understanding of its mechanism. The review also summarizes recent discoveries related to the visualization of MMR components and discusses how it has helped shape our understanding of the coupling of mismatch recognition to replication. Finally, the author explains how visualization of MMR components has paved the way to the study of spontaneous mutations in living cells in real time.
Collapse
Affiliation(s)
- Marina Elez
- Micalis Institute, INRAE, AgroParisTech, Université Paris-Saclay, 78350 Jouy-en-Josas, France;
- Laboratoire Jean Perrin (LJP), Institut de Biologie Paris-Seine (IBPS), CNRS, Sorbonne Université, F-75005 Paris, France
| |
Collapse
|
12
|
Ortega J, Lee GS, Gu L, Yang W, Li GM. Mispair-bound human MutS-MutL complex triggers DNA incisions and activates mismatch repair. Cell Res 2021; 31:542-553. [PMID: 33510387 PMCID: PMC8089094 DOI: 10.1038/s41422-021-00468-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 12/17/2020] [Indexed: 01/30/2023] Open
Abstract
DNA mismatch repair (MMR) relies on MutS and MutL ATPases for mismatch recognition and strand-specific nuclease recruitment to remove mispaired bases in daughter strands. However, whether the MutS-MutL complex coordinates MMR by ATP-dependent sliding on DNA or protein-protein interactions between the mismatch and strand discrimination signal is ambiguous. Using functional MMR assays and systems preventing proteins from sliding, we show that sliding of human MutSα is required not for MMR initiation, but for final mismatch removal. MutSα recruits MutLα to form a mismatch-bound complex, which initiates MMR by nicking the daughter strand 5' to the mismatch. Exonuclease 1 (Exo1) is then recruited to the nick and conducts 5' → 3' excision. ATP-dependent MutSα dissociation from the mismatch is necessary for Exo1 to remove the mispaired base when the excision reaches the mismatch. Therefore, our study has resolved a long-standing puzzle, and provided new insights into the mechanism of MMR initiation and mispair removal.
Collapse
Affiliation(s)
- Janice Ortega
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX USA
| | - Grace Sanghee Lee
- Department of Toxicology and Cancer Biology, University of Kentucky College of Medicine, Lexington, KY USA ,Present Address: Division of Viral Hepatitis, National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Liya Gu
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX USA
| | - Wei Yang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD USA
| | - Guo-Min Li
- Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX USA ,Department of Toxicology and Cancer Biology, University of Kentucky College of Medicine, Lexington, KY USA
| |
Collapse
|
13
|
Perry SA, Kubareva EA, Monakhova MV, Trikin RM, Kosaretskiy EM, Romanova EA, Metelev VG, Friedhoff P, Oretskaya TS. DNA with a 2-Pyridyldithio Group at the C2' Atom: A Promising Tool for the Crosslinking of the MutS Protein Preserving Its Functional Activity. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2021. [DOI: 10.1134/s1068162021020205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
14
|
The selection process of licensing a DNA mismatch for repair. Nat Struct Mol Biol 2021; 28:373-381. [PMID: 33820992 DOI: 10.1038/s41594-021-00577-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2020] [Accepted: 02/19/2021] [Indexed: 01/04/2023]
Abstract
DNA mismatch repair detects and removes mismatches from DNA by a conserved mechanism, reducing the error rate of DNA replication by 100- to 1,000-fold. In this process, MutS homologs scan DNA, recognize mismatches and initiate repair. How the MutS homologs selectively license repair of a mismatch among millions of matched base pairs is not understood. Here we present four cryo-EM structures of Escherichia coli MutS that provide snapshots, from scanning homoduplex DNA to mismatch binding and MutL activation via an intermediate state. During scanning, the homoduplex DNA forms a steric block that prevents MutS from transitioning into the MutL-bound clamp state, which can only be overcome through kinking of the DNA at a mismatch. Structural asymmetry in all four structures indicates a division of labor between the two MutS monomers. Together, these structures reveal how a small conformational change from the homoduplex- to heteroduplex-bound MutS acts as a licensing step that triggers a dramatic conformational change that enables MutL binding and initiation of the repair cascade.
Collapse
|
15
|
Cicconi A, Micheli E, Raffa GD, Cacchione S. Atomic Force Microscopy Reveals that the Drosophila Telomere-Capping Protein Verrocchio Is a Single-Stranded DNA-Binding Protein. Methods Mol Biol 2021; 2281:241-263. [PMID: 33847963 DOI: 10.1007/978-1-0716-1290-3_15] [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] [Indexed: 06/12/2023]
Abstract
Atomic force microscopy (AFM) is a scanning probe technique that allows visualization of biological samples with a nanometric resolution. Determination of the physical properties of biological molecules at a single-molecule level is achieved through topographic analysis of the sample adsorbed on a flat and smooth surface. AFM has been widely used for the structural analysis of nucleic acid-protein interactions, providing insights on binding specificity and stoichiometry of proteins forming complexes with DNA substrates. Analysis of single-stranded DNA-binding proteins by AFM requires specific single-stranded/double-stranded hybrid DNA molecules as substrates for protein binding. In this chapter we describe the protocol for AFM characterization of binding properties of Drosophila telomeric protein Ver using DNA constructs that mimic the structure of chromosome ends. We provide details on the methodology used, including the procedures for the generation of DNA substrates, the preparation of samples for AFM visualization, and the data analysis of AFM images. The presented procedure can be adapted for the structural studies of any single-stranded DNA-binding protein.
Collapse
Affiliation(s)
- Alessandro Cicconi
- Dipartimento di Biologia e Biotecnologie 'C. Darwin', Sapienza, Università di Roma, Rome, Italy.
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, CT, USA.
| | - Emanuela Micheli
- Dipartimento di Biologia e Biotecnologie 'C. Darwin', Sapienza, Università di Roma, Rome, Italy
| | - Grazia Daniela Raffa
- Dipartimento di Biologia e Biotecnologie 'C. Darwin', Sapienza, Università di Roma, Rome, Italy
| | - Stefano Cacchione
- Dipartimento di Biologia e Biotecnologie 'C. Darwin', Sapienza, Università di Roma, Rome, Italy.
| |
Collapse
|
16
|
Cambré A, Aertsen A. Bacterial Vivisection: How Fluorescence-Based Imaging Techniques Shed a Light on the Inner Workings of Bacteria. Microbiol Mol Biol Rev 2020; 84:e00008-20. [PMID: 33115939 PMCID: PMC7599038 DOI: 10.1128/mmbr.00008-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The rise in fluorescence-based imaging techniques over the past 3 decades has improved the ability of researchers to scrutinize live cell biology at increased spatial and temporal resolution. In microbiology, these real-time vivisections structurally changed the view on the bacterial cell away from the "watery bag of enzymes" paradigm toward the perspective that these organisms are as complex as their eukaryotic counterparts. Capitalizing on the enormous potential of (time-lapse) fluorescence microscopy and the ever-extending pallet of corresponding probes, initial breakthroughs were made in unraveling the localization of proteins and monitoring real-time gene expression. However, later it became clear that the potential of this technique extends much further, paving the way for a focus-shift from observing single events within bacterial cells or populations to obtaining a more global picture at the intra- and intercellular level. In this review, we outline the current state of the art in fluorescence-based vivisection of bacteria and provide an overview of important case studies to exemplify how to use or combine different strategies to gain detailed information on the cell's physiology. The manuscript therefore consists of two separate (but interconnected) parts that can be read and consulted individually. The first part focuses on the fluorescent probe pallet and provides a perspective on modern methodologies for microscopy using these tools. The second section of the review takes the reader on a tour through the bacterial cell from cytoplasm to outer shell, describing strategies and methods to highlight architectural features and overall dynamics within cells.
Collapse
Affiliation(s)
- Alexander Cambré
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, Leuven, Belgium
| | - Abram Aertsen
- KU Leuven, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, Leuven, Belgium
| |
Collapse
|
17
|
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.
Collapse
|
18
|
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: 21] [Impact Index Per Article: 5.3] [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.
Collapse
|
19
|
Mardenborough YSN, Nitsenko K, Laffeber C, Duboc C, Sahin E, Quessada-Vial A, Winterwerp HHK, Sixma TK, Kanaar R, Friedhoff P, Strick TR, Lebbink JHG. The unstructured linker arms of MutL enable GATC site incision beyond roadblocks during initiation of DNA mismatch repair. Nucleic Acids Res 2020; 47:11667-11680. [PMID: 31598722 PMCID: PMC6902014 DOI: 10.1093/nar/gkz834] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 08/31/2019] [Accepted: 10/04/2019] [Indexed: 12/30/2022] Open
Abstract
DNA mismatch repair (MMR) maintains genome stability through repair of DNA replication errors. In Escherichia coli, initiation of MMR involves recognition of the mismatch by MutS, recruitment of MutL, activation of endonuclease MutH and DNA strand incision at a hemimethylated GATC site. Here, we studied the mechanism of communication that couples mismatch recognition to daughter strand incision. We investigated the effect of catalytically-deficient Cas9 as well as stalled RNA polymerase as roadblocks placed on DNA in between the mismatch and GATC site in ensemble and single molecule nanomanipulation incision assays. The MMR proteins were observed to incise GATC sites beyond a roadblock, albeit with reduced efficiency. This residual incision is completely abolished upon shortening the disordered linker regions of MutL. These results indicate that roadblock bypass can be fully attributed to the long, disordered linker regions in MutL and establish that communication during MMR initiation occurs along the DNA backbone.
Collapse
Affiliation(s)
| | - Katerina Nitsenko
- Institut Jacques Monod, CNRS, UMR7592, University Paris Diderot, Sorbonne Paris Cité, F-75205 Paris, France
| | - Charlie Laffeber
- Department of Molecular Genetics, Erasmus University Medical Center, Rotterdam, the Netherlands.,Oncode Institute, the Netherlands
| | - Camille Duboc
- Institut Jacques Monod, CNRS, UMR7592, University Paris Diderot, Sorbonne Paris Cité, F-75205 Paris, France
| | - Enes Sahin
- Department of Molecular Genetics, Erasmus University Medical Center, Rotterdam, the Netherlands
| | - Audrey Quessada-Vial
- Institut Jacques Monod, CNRS, UMR7592, University Paris Diderot, Sorbonne Paris Cité, F-75205 Paris, France
| | | | - Titia K Sixma
- Oncode Institute, the Netherlands.,Division of Biochemistry, Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Roland Kanaar
- Department of Molecular Genetics, Erasmus University Medical Center, Rotterdam, the Netherlands.,Oncode Institute, the Netherlands
| | - Peter Friedhoff
- Institute for Biochemistry, Justus-Liebig University, Giessen, Germany
| | - Terence R Strick
- Institut Jacques Monod, CNRS, UMR7592, University Paris Diderot, Sorbonne Paris Cité, F-75205 Paris, France.,Ecole Normale Supérieure, Institut de Biologie de l'Ecole Normale Superieure, CNRS, INSERM, PSL Research University, 75005 Paris, France.,Programme "Equipe Labellisée", Ligue Nationale contre le Cancer
| | - Joyce H G Lebbink
- Department of Molecular Genetics, Erasmus University Medical Center, Rotterdam, the Netherlands.,Department of Radiation Oncology, Erasmus University Medical Center, Rotterdam, the Netherlands
| |
Collapse
|
20
|
Ablenas CJ, Gidi Y, Powdrill MH, Ahmed N, Shaw TA, Mesko M, Götte M, Cosa G, Pezacki JP. Hepatitis C Virus Helicase Binding Activity Monitored through Site-Specific Labeling Using an Expanded Genetic Code. ACS Infect Dis 2019; 5:2118-2126. [PMID: 31640339 DOI: 10.1021/acsinfecdis.9b00220] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mechanism of unwinding catalyzed by the hepatitis C virus nonstructural protein 3 helicase (NS3h) has been a subject of considerable interest, with NS3h serving as a prototypical enzyme in the study of helicase function. Recent studies support an ATP-fueled, inchworm-like stepping of NS3h on the nucleic acid that would result in the displacement of the complementary strand of the duplex during unwinding. Here, we describe the screening of a site of incorporation of an unnatural amino acid in NS3h for fluorescent labeling of the enzyme to be used in single-molecule Förster resonance energy transfer (FRET) experiments. From the nine potential sites identified in NS3h for incorporation of the unnatural amino acid, only one allowed for expression and fluorescent labeling of the recombinant protein. Incorporation of the unnatural amino acid was confirmed via bulk assays to not interfere with unwinding activity of the helicase. Binding to four different dsDNA sequences bearing a ssDNA overhang segment of varying length (either minimal 6 or 7 base length overhang to ensure binding or a long 24 base overhang) and sequence was recorded with the new NS3h construct at the single-molecule level. Single-molecule fluorescence displayed time intervals with anticorrelated donor and acceptor emission fluctuations associated with protein binding to the substrates. An apparent FRET value was estimated from the binding events showing a single FRET value of ∼0.8 for the 6-7 base overhangs. A smaller mean value and a broad distribution was in turn recorded for the long ssDNA overhang, consistent with NS3h exploring a larger physical space while bound to the DNA construct. Notably, intervals where NS3h binding was recorded were exhibited at time periods where the acceptor dye reversibly bleached. Protein induced fluorescence intensity enhancement in the donor channel became apparent at these intervals. Overall, the site-specific fluorescent labeling of NS3h reported here provides a powerful tool for future studies to monitor the dynamics of enzyme translocation during unwinding by single-molecule FRET.
Collapse
Affiliation(s)
- Christopher J. Ablenas
- Department of Biochemistry, McGill University, Montreal, Quebec H3G1Y6, Canada
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N6N5, Canada
| | - Yasser Gidi
- Department of Chemistry, McGill University, Montreal, Quebec H3A0B8, Canada
| | - Megan H. Powdrill
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N6N5, Canada
| | - Noreen Ahmed
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N6N5, Canada
| | - Tyler A. Shaw
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N6N5, Canada
| | - Mihai Mesko
- Department of Chemistry, McGill University, Montreal, Quebec H3A0B8, Canada
| | - Matthias Götte
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta T6G2R7, Canada
| | - Gonzalo Cosa
- Department of Chemistry, McGill University, Montreal, Quebec H3A0B8, Canada
| | - John Paul Pezacki
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N6N5, Canada
| |
Collapse
|
21
|
Broadwater DWB, Altman RB, Blanchard SC, Kim HD. ERASE: a novel surface reconditioning strategy for single-molecule experiments. Nucleic Acids Res 2019; 47:e14. [PMID: 30462308 PMCID: PMC6379648 DOI: 10.1093/nar/gky1168] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Revised: 10/02/2018] [Accepted: 11/01/2018] [Indexed: 11/13/2022] Open
Abstract
While surface-based single-molecule experiments have revolutionized our understanding of biology and biomolecules, the workflow in preparing for such experiments, especially surface cleaning and functionalization, remains labor-intensive and time-consuming. Even worse, meticulously assembled flow channels can be used only once for most experiments. A reusable surface would thus dramatically increase productivity and efficiency of single-molecule experiments. In this paper, we report a novel surface reconditioning strategy termed ERASE (Epitaxial Removal Aided by Strand Exchange) that allows a single flow cell to be used for vast repetition of single-molecule experiments. In this method, biomolecules immobilized to the surface through a nucleic acid duplex are liberated when a competing DNA strand disrupts the duplex via toehold-mediated strand displacement. We demonstrate the wide-range applicability of this method with various common surface preparation techniques, fluorescent dyes, and biomolecules including the bacterial ribosome. Beyond time and cost savings, we also show ERASE can assort molecules based on a nucleic acid barcode sequence, thus allowing experiments on different molecules in parallel. Our method increases the utility of prepared surfaces and is a significant improvement to the current single-use paradigm.
Collapse
Affiliation(s)
- D W Bo Broadwater
- School of Physics, Georgia Institute of Technology, 770 State Street NW, Atlanta, GA 30318, USA
| | - Roger B Altman
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, USA
| | - Scott C Blanchard
- Department of Physiology and Biophysics, Weill Cornell Medicine, New York, NY, USA
| | - Harold D Kim
- School of Physics, Georgia Institute of Technology, 770 State Street NW, Atlanta, GA 30318, USA
| |
Collapse
|
22
|
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.
Collapse
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
| |
Collapse
|
23
|
Shen M, Zhang H, Shen W, Zou Z, Lu S, Li G, He X, Agnello M, Shi W, Hu F, Le S. Pseudomonas aeruginosa MutL promotes large chromosomal deletions through non-homologous end joining to prevent bacteriophage predation. Nucleic Acids Res 2019. [PMID: 29514250 PMCID: PMC5961081 DOI: 10.1093/nar/gky160] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen with a relatively large genome, and has been shown to routinely lose genomic fragments during environmental selection. However, the underlying molecular mechanisms that promote chromosomal deletion are still poorly understood. In a recent study, we showed that by deleting a large chromosomal fragment containing two closely situated genes, hmgA and galU, P. aeruginosa was able to form ‘brown mutants’, bacteriophage (phage) resistant mutants with a brown color phenotype. In this study, we show that the brown mutants occur at a frequency of 227 ± 87 × 10−8 and contain a deletion ranging from ∼200 to ∼620 kb. By screening P. aeruginosa transposon mutants, we identified mutL gene whose mutation constrained the emergence of phage-resistant brown mutants. Moreover, the P. aeruginosa MutL (PaMutL) nicking activity can result in DNA double strand break (DSB), which is then repaired by non-homologous end joining (NHEJ), leading to chromosomal deletions. Thus, we reported a noncanonical function of PaMutL that promotes chromosomal deletions through NHEJ to prevent phage predation.
Collapse
Affiliation(s)
- Mengyu Shen
- Department of Microbiology, Third Military Medical University, Chongqing 400038, China
| | - Huidong Zhang
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing 400038, China
| | - Wei Shen
- Department of Medical Laboratory, Chengdu Military General Hospital, Chengdu 610083, China
| | - Zhenyu Zou
- Institute of Toxicology, College of Preventive Medicine, Third Military Medical University, Chongqing 400038, China
| | - Shuguang Lu
- Department of Microbiology, Third Military Medical University, Chongqing 400038, China
| | - Gang Li
- Department of Microbiology, Third Military Medical University, Chongqing 400038, China
| | - Xuesong He
- The Forsyth Institute, 245 First St, Cambridge, MA 02142, USA
| | - Melissa Agnello
- School of Dentistry, University of California, Los Angeles, CA 90095, USA
| | - Wenyuan Shi
- The Forsyth Institute, 245 First St, Cambridge, MA 02142, USA
| | - Fuquan Hu
- Department of Microbiology, Third Military Medical University, Chongqing 400038, China
| | - Shuai Le
- Department of Microbiology, Third Military Medical University, Chongqing 400038, China
| |
Collapse
|
24
|
Single gold-bridged nanoprobes for identification of single point DNA mutations. Nat Commun 2019; 10:836. [PMID: 30783107 PMCID: PMC6381086 DOI: 10.1038/s41467-019-08769-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2018] [Accepted: 01/23/2019] [Indexed: 01/15/2023] Open
Abstract
Consensus ranking of protein affinity to identify point mutations has not been established. Therefore, analytical techniques that can detect subtle variations without interfering with native biomolecular interactions are required. Here we report a rapid method to identify point mutations by a single nanoparticle sensing system. DNA-directed gold crystallization forms rod-like nanoparticles with bridges based on structural design. The nanoparticles enhance Rayleigh light scattering, achieving high refractive-index sensitivity, and enable the system to monitor even a small number of protein-DNA binding events without interference. Analysis of the binding affinity can compile an atlas to distinguish the potential of various point mutations recognized by MutS protein. We use the atlas to analyze the presence and type of single point mutations in BRCA1 from samples of human breast and ovarian cancer cell lines. The strategy of synthesis-by-design of plasmonic nanoparticles for sensors enables direct identification of subtle biomolecular binding distortions and genetic alterations.
Collapse
|
25
|
Gao B, Chi L, Tu P, Gao N, Lu K. The Carbamate Aldicarb Altered the Gut Microbiome, Metabolome, and Lipidome of C57BL/6J Mice. Chem Res Toxicol 2019; 32:67-79. [PMID: 30406643 DOI: 10.1021/acs.chemrestox.8b00179] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The gut microbiome is highly involved in numerous aspects of host physiology, from energy harvest to stress response, and can confer many benefits to the host. The gut microbiome development could be affected by genetic and environmental factors, including pesticides. The carbamate insecticide aldicarb has been extensively used in agriculture, which raises serious public health concerns. However, the impact of aldicarb on the gut microbiome, host metabolome, and lipidome has not been well studied yet. Herein, we use multiomics approaches, including16S rRNA sequencing, shotgun metagenomics sequencing, metabolomics, and lipidomics, to elucidate aldicarb-induced toxicity in the gut microbiome and the host metabolic homeostasis. We demonstrated that aldicarb perturbed the gut microbiome development trajectory, enhanced gut bacterial pathogenicity, altered complex lipid profile, and induced oxidative stress, protein degradation, and DNA damage. The brain metabolism was also disturbed by the aldicarb exposure. These findings may provide a novel understanding of the toxicity of carbamate insecticides.
Collapse
Affiliation(s)
- Bei Gao
- Department of Environmental Sciences and Engineering , University of North Carolina at Chapel Hill , Chapel Hill , North Carolina 27599 , United States.,NIH West Coast Metabolomics Center , University of California , Davis , California 95616 , United States
| | - Liang Chi
- Department of Environmental Sciences and Engineering , University of North Carolina at Chapel Hill , Chapel Hill , North Carolina 27599 , United States
| | - Pengcheng Tu
- Department of Environmental Sciences and Engineering , University of North Carolina at Chapel Hill , Chapel Hill , North Carolina 27599 , United States
| | - Nan Gao
- National Engineering Research Center for Biotechnology, School of Biotechnology and Pharmaceutical Engineering , Nanjing Tech University , Nanjing 211816 , China
| | - Kun Lu
- Department of Environmental Sciences and Engineering , University of North Carolina at Chapel Hill , Chapel Hill , North Carolina 27599 , United States
| |
Collapse
|
26
|
Liu J, Lee JB, Fishel R. Stochastic Processes and Component Plasticity Governing DNA Mismatch Repair. J Mol Biol 2018; 430:4456-4468. [PMID: 29864444 PMCID: PMC6461355 DOI: 10.1016/j.jmb.2018.05.039] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 05/09/2018] [Accepted: 05/28/2018] [Indexed: 02/06/2023]
Abstract
DNA mismatch repair (MMR) is a DNA excision-resynthesis process that principally enhances replication fidelity. Highly conserved MutS (MSH) and MutL (MLH/PMS) homologs initiate MMR and in higher eukaryotes act as DNA damage sensors that can trigger apoptosis. MSH proteins recognize mismatched nucleotides, whereas the MLH/PMS proteins mediate multiple interactions associated with downstream MMR events including strand discrimination and strand-specific excision that are initiated at a significant distance from the mismatch. Remarkably, the biophysical functions of the MLH/PMS proteins have been elusive for decades. Here we consider recent observations that have helped to define the mechanics of MLH/PMS proteins and their role in choreographing MMR. We highlight the stochastic nature of DNA interactions that have been visualized by single-molecule analysis and the plasticity of protein complexes that employ thermal diffusion to complete the progressions of MMR.
Collapse
Affiliation(s)
- Jiaquan Liu
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, 43210, OH, USA
| | - Jong-Bong Lee
- Department of Physics, Pohang University of Science and Technology (POSTECH), 790-784, Pohang, Korea; Interdisciplinary Bioscience and Bioengineering, POSTECH, 790-784, Pohang, Korea.
| | - Richard Fishel
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, 43210, OH, USA.
| |
Collapse
|
27
|
Josephs EA, Marszalek PE. Endonuclease-independent DNA mismatch repair processes on the lagging strand. DNA Repair (Amst) 2018; 68:41-49. [PMID: 29929046 DOI: 10.1016/j.dnarep.2018.06.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 05/04/2018] [Accepted: 06/11/2018] [Indexed: 12/31/2022]
Abstract
DNA mismatch repair (MMR) pathways coordinate the excision and re-synthesis of newly-replicated DNA if a mismatched base-pair has been identified by protein MutS or MutS homologues (MSHs) after replication. DNA excision during MMR is initiated at single-strand breaks (SSBs) in vitro, and several redundant processes have been observed in reconstituted systems which either require a pre-formed SSB in the DNA or require a mismatch-activated nicking endonuclease to introduce a SSB in order to initiate MMR. However, the conditions under which each of these processes may actually occur in living cells have remained obscured by the limitations of current MMR assays. Here we use a novel assay involving chemically-modified oligonucleotide probes to insert targeted DNA 'mismatches' directly into the genome of living bacteria to interrogate their replication-coupled repair processes quantitatively in a strand-, orientation-, and mismatched nucleotide-specific manner. This 'semi-protected oligonucleotide recombination' (SPORE) assay reveals direct evidence in Escherichia coli of an efficient endonuclease-independent MMR process on the lagging strand-a mechanism that has long-since been considered for lagging-strand repair but never directly shown until now. We find endonuclease-independent MMR is coordinated asymmetrically with respect to the replicating DNA-directed primarily from 3'- of the mismatch-and that repair coordinated from 3'- of the mismatch is in fact the primary mechanism of lagging-strand MMR. While further work is required to explore and identify the molecular requirements for this alternative endonuclease-independent MMR pathway, these findings made possible using the SPORE assay are the first direct report of this long-suspected mechanism in vivo.
Collapse
Affiliation(s)
- Eric A Josephs
- Department of Mechanical Engineering and Materials Science, Edmund T. Pratt, Jr. School of Engineering, Duke University, Durham, NC, USA.
| | - Piotr E Marszalek
- Department of Mechanical Engineering and Materials Science, Edmund T. Pratt, Jr. School of Engineering, Duke University, Durham, NC, USA.
| |
Collapse
|
28
|
Binder H, Hopp L, Schweiger MR, Hoffmann S, Jühling F, Kerick M, Timmermann B, Siebert S, Grimm C, Nersisyan L, Arakelyan A, Herberg M, Buske P, Loeffler-Wirth H, Rosolowski M, Engel C, Przybilla J, Peifer M, Friedrichs N, Moeslein G, Odenthal M, Hussong M, Peters S, Holzapfel S, Nattermann J, Hueneburg R, Schmiegel W, Royer-Pokora B, Aretz S, Kloth M, Kloor M, Buettner R, Galle J, Loeffler M. Genomic and transcriptomic heterogeneity of colorectal tumours arising in Lynch syndrome. J Pathol 2017; 243:242-254. [DOI: 10.1002/path.4948] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 06/01/2017] [Accepted: 07/14/2017] [Indexed: 12/16/2022]
Affiliation(s)
- Hans Binder
- Interdisciplinary Centre for Bioinformatics; Leipzig University; Leipzig Germany
| | - Lydia Hopp
- Interdisciplinary Centre for Bioinformatics; Leipzig University; Leipzig Germany
| | - Michal R Schweiger
- Institute of Pathology, Centre for Integrated Oncology; University Hospital Cologne; Cologne Germany
- Translational Epigenomics; University Hospital Cologne; Cologne Germany
- Max Planck Institute for Molecular Genetics; Berlin Germany
| | - Steve Hoffmann
- Interdisciplinary Centre for Bioinformatics; Leipzig University; Leipzig Germany
| | - Frank Jühling
- Interdisciplinary Centre for Bioinformatics; Leipzig University; Leipzig Germany
- Inserm, U1110, Institut de Recherche sur les Maladies Virales et Hépatiques; Strasbourg France
- Université de Strasbourg; Strasbourg France
| | - Martin Kerick
- Institute of Pathology, Centre for Integrated Oncology; University Hospital Cologne; Cologne Germany
- Translational Epigenomics; University Hospital Cologne; Cologne Germany
- Max Planck Institute for Molecular Genetics; Berlin Germany
| | | | - Susann Siebert
- Institute of Pathology, Centre for Integrated Oncology; University Hospital Cologne; Cologne Germany
- Translational Epigenomics; University Hospital Cologne; Cologne Germany
- Max Planck Institute for Molecular Genetics; Berlin Germany
| | - Christina Grimm
- Institute of Pathology, Centre for Integrated Oncology; University Hospital Cologne; Cologne Germany
- Translational Epigenomics; University Hospital Cologne; Cologne Germany
- Max Planck Institute for Molecular Genetics; Berlin Germany
| | - Lilit Nersisyan
- Group of Bioinformatics, Institute of Molecular Biology; National Academy of Sciences; Yerevan Armenia
| | - Arsen Arakelyan
- Group of Bioinformatics, Institute of Molecular Biology; National Academy of Sciences; Yerevan Armenia
| | - Maria Herberg
- Interdisciplinary Centre for Bioinformatics; Leipzig University; Leipzig Germany
| | - Peter Buske
- Interdisciplinary Centre for Bioinformatics; Leipzig University; Leipzig Germany
| | - Henry Loeffler-Wirth
- Interdisciplinary Centre for Bioinformatics; Leipzig University; Leipzig Germany
| | - Maciej Rosolowski
- Institute for Medical Informatics, Statistics and Epidemiology; Leipzig University; Leipzig Germany
| | - Christoph Engel
- Institute for Medical Informatics, Statistics and Epidemiology; Leipzig University; Leipzig Germany
| | - Jens Przybilla
- Interdisciplinary Centre for Bioinformatics; Leipzig University; Leipzig Germany
| | - Martin Peifer
- Institute of Pathology, Centre for Integrated Oncology; University Hospital Cologne; Cologne Germany
| | - Nicolaus Friedrichs
- Institute of Pathology, Centre for Integrated Oncology; University Hospital Cologne; Cologne Germany
| | - Gabriela Moeslein
- Department of Hereditary Tumour Syndromes; Surgical Centre, HELIOS Clinic, University Witten/Herdecke; Wuppertal Germany
| | - Margarete Odenthal
- Institute of Pathology, Centre for Integrated Oncology; University Hospital Cologne; Cologne Germany
| | - Michelle Hussong
- Institute of Pathology, Centre for Integrated Oncology; University Hospital Cologne; Cologne Germany
- Translational Epigenomics; University Hospital Cologne; Cologne Germany
- Max Planck Institute for Molecular Genetics; Berlin Germany
| | - Sophia Peters
- Institute of Human Genetics, University Hospital Bonn; Centre for Hereditary Tumour Syndromes, University of Bonn; Bonn Germany
| | - Stefanie Holzapfel
- Institute of Human Genetics, University Hospital Bonn; Centre for Hereditary Tumour Syndromes, University of Bonn; Bonn Germany
| | - Jacob Nattermann
- Department of Internal Medicine I, University Hospital Bonn; Centre for Hereditary Tumour Syndromes, University of Bonn; Bonn Germany
| | - Robert Hueneburg
- Department of Internal Medicine I, University Hospital Bonn; Centre for Hereditary Tumour Syndromes, University of Bonn; Bonn Germany
| | - Wolff Schmiegel
- Department of Medicine, Haematology and Oncology; Ruhr-University of Bochum, Knappschaftskrankenhaus; Bochum Germany
| | - Brigitte Royer-Pokora
- Institute of Human Genetics and Anthropology; Heinrich-Heine University; Düsseldorf Germany
| | - Stefan Aretz
- Institute of Human Genetics, University Hospital Bonn; Centre for Hereditary Tumour Syndromes, University of Bonn; Bonn Germany
| | - Michael Kloth
- Institute of Pathology, Centre for Integrated Oncology; University Hospital Cologne; Cologne Germany
| | - Matthias Kloor
- Department of Applied Tumour Biology, Institute of Pathology; University Hospital Heidelberg; Heidelberg Germany
- Clinical Cooperation Unit of Applied Tumour Biology; DKFZ (German Cancer Research Centre) Heidelberg; Germany
- Molecular Medicine Partnership Unit; University Hospital Heidelberg and EMBL Heidelberg; Heidelberg Germany
| | - Reinhard Buettner
- Institute of Pathology, Centre for Integrated Oncology; University Hospital Cologne; Cologne Germany
| | - Jörg Galle
- Interdisciplinary Centre for Bioinformatics; Leipzig University; Leipzig Germany
| | - Markus Loeffler
- Institute for Medical Informatics, Statistics and Epidemiology; Leipzig University; Leipzig Germany
| |
Collapse
|
29
|
Friedhoff P, Manelyte L, Giron-Monzon L, Winkler I, Groothuizen FS, Sixma TK. Use of Single-Cysteine Variants for Trapping Transient States in DNA Mismatch Repair. Methods Enzymol 2017; 592:77-101. [PMID: 28668131 DOI: 10.1016/bs.mie.2017.03.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
DNA mismatch repair (MMR) is necessary to prevent incorporation of polymerase errors into the newly synthesized DNA strand, as they would be mutagenic. In humans, errors in MMR cause a predisposition to cancer, called Lynch syndrome. The MMR process is performed by a set of ATPases that transmit, validate, and couple information to identify which DNA strand requires repair. To understand the individual steps in the repair process, it is useful to be able to study these large molecular machines structurally and functionally. However, the steps and states are highly transient; therefore, the methods to capture and enrich them are essential. Here, we describe how single-cysteine variants can be used for specific cross-linking and labeling approaches that allow trapping of relevant transient states. Analysis of these defined states in functional and structural studies is instrumental to elucidate the molecular mechanism of this important DNA MMR process.
Collapse
Affiliation(s)
- Peter Friedhoff
- Institute for Biochemistry, Justus-Liebig-University, Giessen, Germany.
| | - Laura Manelyte
- Institute for Biochemistry, Justus-Liebig-University, Giessen, Germany
| | - Luis Giron-Monzon
- Institute for Biochemistry, Justus-Liebig-University, Giessen, Germany
| | - Ines Winkler
- Institute for Biochemistry, Justus-Liebig-University, Giessen, Germany
| | | | - Titia K Sixma
- Netherlands Cancer Institute, Amsterdam, The Netherlands.
| |
Collapse
|
30
|
Beckwitt EC, Kong M, Van Houten B. Studying protein-DNA interactions using atomic force microscopy. Semin Cell Dev Biol 2017; 73:220-230. [PMID: 28673677 DOI: 10.1016/j.semcdb.2017.06.028] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 06/27/2017] [Accepted: 06/29/2017] [Indexed: 12/12/2022]
Abstract
Atomic force microscopy (AFM) has made significant contributions to the study of protein-DNA interactions by making it possible to topographically image biological samples. A single protein-DNA binding reaction imaged by AFM can reveal protein binding specificity and affinity, protein-induced DNA bending, and protein binding stoichiometry. Changes in DNA structure, complex conformation, and cooperativity, can also be analyzed. In this review we highlight some important examples in the literature and discuss the advantages and limitations of these measurements. We also discuss important advances in technology that will facilitate the progress of AFM in the future.
Collapse
Affiliation(s)
- Emily C Beckwitt
- Program in Molecular Biophysics and Structural Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA; The University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA 15213, USA
| | - Muwen Kong
- Program in Molecular Biophysics and Structural Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA; The University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA 15213, USA
| | - Bennett Van Houten
- Program in Molecular Biophysics and Structural Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA; The University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA 15213, USA; Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA.
| |
Collapse
|
31
|
LeBlanc S, Wilkins H, Li Z, Kaur P, Wang H, Erie DA. Using Atomic Force Microscopy to Characterize the Conformational Properties of Proteins and Protein-DNA Complexes That Carry Out DNA Repair. Methods Enzymol 2017; 592:187-212. [PMID: 28668121 PMCID: PMC5761736 DOI: 10.1016/bs.mie.2017.04.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Atomic force microscopy (AFM) is a scanning probe technique that allows visualization of single biomolecules and complexes deposited on a surface with nanometer resolution. AFM is a powerful tool for characterizing protein-protein and protein-DNA interactions. It can be used to capture snapshots of protein-DNA solution dynamics, which in turn, enables the characterization of the conformational properties of transient protein-protein and protein-DNA interactions. With AFM, it is possible to determine the stoichiometries and binding affinities of protein-protein and protein-DNA associations, the specificity of proteins binding to specific sites on DNA, and the conformations of the complexes. We describe methods to prepare and deposit samples, including surface treatments for optimal depositions, and how to quantitatively analyze images. We also discuss a new electrostatic force imaging technique called DREEM, which allows the visualization of the path of DNA within proteins in protein-DNA complexes. Collectively, these methods facilitate the development of comprehensive models of DNA repair and provide a broader understanding of all protein-protein and protein-nucleic acid interactions. The structural details gleaned from analysis of AFM images coupled with biochemistry provide vital information toward establishing the structure-function relationships that govern DNA repair processes.
Collapse
Affiliation(s)
- Sharonda LeBlanc
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Hunter Wilkins
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Zimeng Li
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Parminder Kaur
- North Carolina State University, Raleigh, NC, United States
| | - Hong Wang
- North Carolina State University, Raleigh, NC, United States
| | - Dorothy A Erie
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.
| |
Collapse
|
32
|
Chatterjee N, Walker GC. Mechanisms of DNA damage, repair, and mutagenesis. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2017; 58:235-263. [PMID: 28485537 PMCID: PMC5474181 DOI: 10.1002/em.22087] [Citation(s) in RCA: 997] [Impact Index Per Article: 142.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 03/16/2017] [Indexed: 05/08/2023]
Abstract
Living organisms are continuously exposed to a myriad of DNA damaging agents that can impact health and modulate disease-states. However, robust DNA repair and damage-bypass mechanisms faithfully protect the DNA by either removing or tolerating the damage to ensure an overall survival. Deviations in this fine-tuning are known to destabilize cellular metabolic homeostasis, as exemplified in diverse cancers where disruption or deregulation of DNA repair pathways results in genome instability. Because routinely used biological, physical and chemical agents impact human health, testing their genotoxicity and regulating their use have become important. In this introductory review, we will delineate mechanisms of DNA damage and the counteracting repair/tolerance pathways to provide insights into the molecular basis of genotoxicity in cells that lays the foundation for subsequent articles in this issue. Environ. Mol. Mutagen. 58:235-263, 2017. © 2017 Wiley Periodicals, Inc.
Collapse
|
33
|
Abstract
Ubiquitous conserved processes that repair DNA damage are essential for the maintenance and propagation of genomes over generations. Then again, inaccuracies in DNA transactions and failures to remove mutagenic lesions cause heritable genome changes. Building on decades of research using genetics and biochemistry, unprecedented quantitative insight into DNA repair mechanisms has come from the new-found ability to measure single proteins in vitro and inside individual living cells. This has brought together biologists, chemists, engineers, physicists, and mathematicians to solve long-standing questions about the way in which repair enzymes search for DNA lesions and form protein complexes that act in DNA repair pathways. Furthermore, unexpected discoveries have resulted from capabilities to resolve molecular heterogeneity and cell subpopulations, provoking new questions about the role of stochastic processes in DNA repair and mutagenesis. These studies are leading to new technologies that will find widespread use in basic research, biotechnology, and medicine.
Collapse
Affiliation(s)
- Stephan Uphoff
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom; ,
| | - David J Sherratt
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom; ,
| |
Collapse
|
34
|
Lakhani B, Thayer KM, Hingorani MM, Beveridge DL. Evolutionary Covariance Combined with Molecular Dynamics Predicts a Framework for Allostery in the MutS DNA Mismatch Repair Protein. J Phys Chem B 2017; 121:2049-2061. [PMID: 28135092 PMCID: PMC5346969 DOI: 10.1021/acs.jpcb.6b11976] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
![]()
Mismatch
repair (MMR) is an essential, evolutionarily conserved
pathway that maintains genome stability by correcting base-pairing
errors in DNA. Here we examine the sequence and structure of MutS
MMR protein to decipher the amino acid framework underlying its two
key activities—recognizing mismatches in DNA and using ATP
to initiate repair. Statistical coupling analysis (SCA) identified
a network (sector) of coevolved amino acids in the MutS protein family.
The potential functional significance of this SCA sector was assessed
by performing molecular dynamics (MD) simulations for alanine mutants
of the top 5% of 160 residues in the distribution, and control nonsector
residues. The effects on three independent metrics were monitored:
(i) MutS domain conformational dynamics, (ii) hydrogen bonding between
MutS and DNA/ATP, and (iii) relative ATP binding free energy. Each
measure revealed that sector residues contribute more substantively
to MutS structure–function than nonsector residues. Notably,
sector mutations disrupted MutS contacts with DNA and/or ATP from
a distance via contiguous pathways and correlated motions, supporting
the idea that SCA can identify amino acid networks underlying allosteric
communication. The combined SCA/MD approach yielded novel, experimentally
testable hypotheses for unknown roles of many residues distributed
across MutS, including some implicated in Lynch cancer syndrome.
Collapse
Affiliation(s)
- Bharat Lakhani
- Molecular Biology and Biochemistry Department, ‡Molecular Biophysics Program, §Chemistry Department, and ∥Computer Science Department, Wesleyan University , Middletown, Connecticut 06459, United States
| | - Kelly M Thayer
- Molecular Biology and Biochemistry Department, ‡Molecular Biophysics Program, §Chemistry Department, and ∥Computer Science Department, Wesleyan University , Middletown, Connecticut 06459, United States
| | - Manju M Hingorani
- Molecular Biology and Biochemistry Department, ‡Molecular Biophysics Program, §Chemistry Department, and ∥Computer Science Department, Wesleyan University , Middletown, Connecticut 06459, United States
| | - David L Beveridge
- Molecular Biology and Biochemistry Department, ‡Molecular Biophysics Program, §Chemistry Department, and ∥Computer Science Department, Wesleyan University , Middletown, Connecticut 06459, United States
| |
Collapse
|
35
|
Hopfner KP. Invited review: Architectures and mechanisms of ATP binding cassette proteins. Biopolymers 2017; 105:492-504. [PMID: 27037766 DOI: 10.1002/bip.22843] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Revised: 03/24/2016] [Accepted: 03/28/2016] [Indexed: 12/29/2022]
Abstract
ATP binding cassette (ABC) ATPases form chemo-mechanical engines and switches that function in a broad range of biological processes. Most prominently, a very large family of integral membrane NTPases-ABC transporters-catalyzes the import or export of a diverse molecules across membranes. ABC proteins are also important components of the chromosome segregation, recombination, and DNA repair machineries and regulate or catalyze critical steps of ribosomal protein synthesis. Recent structural and mechanistic studies draw interesting architectural and mechanistic parallels between diverse ABC proteins. Here, I review this state of our understanding how NTP-dependent conformational changes of ABC proteins drive diverse biological processes. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 492-504, 2016.
Collapse
Affiliation(s)
- Karl-Peter Hopfner
- Department Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, 81377 Munich, Germany.,Gene Center, Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, 81377 Munich, Germany.,Center for Integrated Protein Science Munich, Ludwigs-Maximilians-Universität München, Feodor-Lynen-Str. 25, 81377 Munich, Germany
| |
Collapse
|
36
|
Liu J, Hanne J, Britton BM, Bennett J, Kim D, Lee JB, Fishel R. Cascading MutS and MutL sliding clamps control DNA diffusion to activate mismatch repair. Nature 2016; 539:583-587. [PMID: 27851738 PMCID: PMC5845140 DOI: 10.1038/nature20562] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 10/21/2016] [Indexed: 01/25/2023]
Abstract
Mismatched nucleotides arise from polymerase misincorporation errors, recombination between heteroallelic parents and chemical or physical DNA damage. Highly conserved MutS (MSH) and MutL (MLH/PMS) homologues initiate mismatch repair and, in higher eukaryotes, act as DNA damage sensors that can trigger apoptosis. Defects in human mismatch repair genes cause Lynch syndrome or hereditary non-polyposis colorectal cancer and 10-40% of related sporadic tumours. However, the collaborative mechanics of MSH and MLH/PMS proteins have not been resolved in any organism. We visualized Escherichia coli (Ec) ensemble mismatch repair and confirmed that EcMutS mismatch recognition results in the formation of stable ATP-bound sliding clamps that randomly diffuse along the DNA with intermittent backbone contact. The EcMutS sliding clamps act as a platform to recruit EcMutL onto the mismatched DNA, forming an EcMutS-EcMutL search complex that then closely follows the DNA backbone. ATP binding by EcMutL establishes a second long-lived DNA clamp that oscillates between the principal EcMutS-EcMutL search complex and unrestricted EcMutS and EcMutL sliding clamps. The EcMutH endonuclease that targets mismatch repair excision only binds clamped EcMutL, increasing its DNA association kinetics by more than 1,000-fold. The assembly of an EcMutS-EcMutL-EcMutH search complex illustrates how sequential stable sliding clamps can modulate one-dimensional diffusion mechanics along the DNA to direct mismatch repair.
Collapse
Affiliation(s)
- Jiaquan Liu
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA
| | - Jeungphill Hanne
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA
| | - Brooke M Britton
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA
| | - Jared Bennett
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA
| | - Daehyung Kim
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, Kyungbuk 790-784, Korea
| | - Jong-Bong Lee
- Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang, Kyungbuk 790-784, Korea
- School of Interdisciplinary Bioscience and Bioengineering, POSTECH, Pohang, Kyungbuk, 790-784, Korea
| | - Richard Fishel
- Department of Cancer Biology and Genetics, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, USA
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| |
Collapse
|
37
|
Kawasoe Y, Tsurimoto T, Nakagawa T, Masukata H, Takahashi TS. MutSα maintains the mismatch repair capability by inhibiting PCNA unloading. eLife 2016; 5. [PMID: 27402201 PMCID: PMC4942255 DOI: 10.7554/elife.15155] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 05/26/2016] [Indexed: 12/03/2022] Open
Abstract
Eukaryotic mismatch repair (MMR) utilizes single-strand breaks as signals to target the strand to be repaired. DNA-bound PCNA is also presumed to direct MMR. The MMR capability must be limited to a post-replicative temporal window during which the signals are available. However, both identity of the signal(s) involved in the retention of this temporal window and the mechanism that maintains the MMR capability after DNA synthesis remain unclear. Using Xenopus egg extracts, we discovered a mechanism that ensures long-term retention of the MMR capability. We show that DNA-bound PCNA induces strand-specific MMR in the absence of strand discontinuities. Strikingly, MutSα inhibited PCNA unloading through its PCNA-interacting motif, thereby extending significantly the temporal window permissive to strand-specific MMR. Our data identify DNA-bound PCNA as the signal that enables strand discrimination after the disappearance of strand discontinuities, and uncover a novel role of MutSα in the retention of the post-replicative MMR capability. DOI:http://dx.doi.org/10.7554/eLife.15155.001 To pass on genetic information from one generation to the next, the DNA in a cell must be precisely copied. DNA is made of two strands and genetic information is encoded by sequences of molecules called bases in the strands. The bases from one strand form pairs with complementary bases on the other strand. However, errors in the copying process result in unmatched pairs of bases. Such errors are corrected by a repair system called mismatch repair. When DNA is copied, the two strands are separated and used as templates to make new complementary strands. This means that errors only arise on the new strands. Mismatch repair must therefore target the new strands to maintain the original information encoded by the template DNA. The repair needs to happen before the copying process is complete because the template strands and the new strands become indistinguishable afterwards. However, it is not clear how the two processes communicate with each other. Previous studies have identified a ring-shaped molecule called the replication clamp – which is essential for the copying process – as a prime candidate for the molecule responsible for this communication. This molecule binds to the DNA to promote the copying process, and afterwards it is removed from the DNA by other molecules. Furthermore, a group of proteins called the MutSα complex, which recognizes unmatched bases in DNA molecules, physically interacts with the replication clamp. Kawasoe et al. used eggs from African clawed frogs to study how the replication clamp connects the copying process and mismatch repair in more detail. The experiments show that when the replication clamp is bound to the DNA, it is able to direct mismatch repair to a specific DNA strand. When MutSα recognizes unmatched bases, it prevents the replication clamp from being removed from the DNA. By doing so, MutSα prevents the information about the new DNA strand from being lost until mismatch repair has taken place. These findings reveal new interactions between DNA copying and the correction of errors by mismatch repair. The next steps will be to understand how MutSα is able to keep the replication clamp on the DNA and to clarify its role in protecting DNA from gaining mutations. DOI:http://dx.doi.org/10.7554/eLife.15155.002
Collapse
Affiliation(s)
| | - Toshiki Tsurimoto
- Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan
| | - Takuro Nakagawa
- Graduate School of Science, Osaka University, Toyonaka, Japan
| | - Hisao Masukata
- Graduate School of Science, Osaka University, Toyonaka, Japan
| | | |
Collapse
|
38
|
Hermans N, Laffeber C, Cristovão M, Artola-Borán M, Mardenborough Y, Ikpa P, Jaddoe A, Winterwerp HHK, Wyman C, Jiricny J, Kanaar R, Friedhoff P, Lebbink JHG. Dual daughter strand incision is processive and increases the efficiency of DNA mismatch repair. Nucleic Acids Res 2016; 44:6770-86. [PMID: 27174933 PMCID: PMC5001592 DOI: 10.1093/nar/gkw411] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 05/03/2016] [Indexed: 12/27/2022] Open
Abstract
DNA mismatch repair (MMR) is an evolutionarily-conserved process responsible for the repair of replication errors. In Escherichia coli, MMR is initiated by MutS and MutL, which activate MutH to incise transiently-hemimethylated GATC sites. MMR efficiency depends on the distribution of these GATC sites. To understand which molecular events determine repair efficiency, we quantitatively studied the effect of strand incision on unwinding and excision activity. The distance between mismatch and GATC site did not influence the strand incision rate, and an increase in the number of sites enhanced incision only to a minor extent. Two GATC sites were incised by the same activated MMR complex in a processive manner, with MutS, the closed form of MutL and MutH displaying different roles. Unwinding and strand excision were more efficient on a substrate with two nicks flanking the mismatch, as compared to substrates containing a single nick or two nicks on the same side of the mismatch. Introduction of multiple nicks by the human MutLα endonuclease also contributed to increased repair efficiency. Our data support a general model of prokaryotic and eukaryotic MMR in which, despite mechanistic differences, mismatch-activated complexes facilitate efficient repair by creating multiple daughter strand nicks.
Collapse
Affiliation(s)
- Nicolaas Hermans
- Department of Molecular Genetics, Cancer Genomics Netherlands, Erasmus Medical Center Rotterdam, 3015 AA Rotterdam,The Netherlands
| | - Charlie Laffeber
- Department of Molecular Genetics, Cancer Genomics Netherlands, Erasmus Medical Center Rotterdam, 3015 AA Rotterdam,The Netherlands
| | - Michele Cristovão
- Department of Molecular Genetics, Cancer Genomics Netherlands, Erasmus Medical Center Rotterdam, 3015 AA Rotterdam,The Netherlands
| | - Mariela Artola-Borán
- Institute of Molecular Cancer Research of the University of Zurich and ETH Zurich, Winterthurerstrasse 190, CH 8057 Zurich, Switzerland
| | - Yannicka Mardenborough
- Department of Molecular Genetics, Cancer Genomics Netherlands, Erasmus Medical Center Rotterdam, 3015 AA Rotterdam,The Netherlands
| | - Pauline Ikpa
- Department of Molecular Genetics, Cancer Genomics Netherlands, Erasmus Medical Center Rotterdam, 3015 AA Rotterdam,The Netherlands
| | - Aruna Jaddoe
- Department of Molecular Genetics, Cancer Genomics Netherlands, Erasmus Medical Center Rotterdam, 3015 AA Rotterdam,The Netherlands
| | - Herrie H K Winterwerp
- Division of Biochemistry and Center for Biomedical Genetics, Netherlands Cancer Institute, 1006 BE Amsterdam, The Netherlands
| | - Claire Wyman
- Department of Molecular Genetics, Cancer Genomics Netherlands, Erasmus Medical Center Rotterdam, 3015 AA Rotterdam,The Netherlands Department of Radiation Oncology, Erasmus Medical Center Rotterdam, 3015 CE Rotterdam, The Netherlands
| | - Josef Jiricny
- Institute of Molecular Cancer Research of the University of Zurich and ETH Zurich, Winterthurerstrasse 190, CH 8057 Zurich, Switzerland
| | - Roland Kanaar
- Department of Molecular Genetics, Cancer Genomics Netherlands, Erasmus Medical Center Rotterdam, 3015 AA Rotterdam,The Netherlands Department of Radiation Oncology, Erasmus Medical Center Rotterdam, 3015 CE Rotterdam, The Netherlands
| | - Peter Friedhoff
- Institute for Biochemistry, Justus-Liebig-University, D-35392 Giessen, Germany
| | - Joyce H G Lebbink
- Department of Molecular Genetics, Cancer Genomics Netherlands, Erasmus Medical Center Rotterdam, 3015 AA Rotterdam,The Netherlands Department of Radiation Oncology, Erasmus Medical Center Rotterdam, 3015 CE Rotterdam, The Netherlands
| |
Collapse
|
39
|
Dynamic control of strand excision during human DNA mismatch repair. Proc Natl Acad Sci U S A 2016; 113:3281-6. [PMID: 26951673 DOI: 10.1073/pnas.1523748113] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Mismatch repair (MMR) is activated by evolutionarily conserved MutS homologs (MSH) and MutL homologs (MLH/PMS). MSH recognizes mismatched nucleotides and form extremely stable sliding clamps that may be bound by MLH/PMS to ultimately authorize strand-specific excision starting at a distant 3'- or 5'-DNA scission. The mechanical processes associated with a complete MMR reaction remain enigmatic. The purified human (Homo sapien or Hs) 5'-MMR excision reaction requires the HsMSH2-HsMSH6 heterodimer, the 5' → 3' exonuclease HsEXOI, and the single-stranded binding heterotrimer HsRPA. The HsMLH1-HsPMS2 heterodimer substantially influences 5'-MMR excision in cell extracts but is not required in the purified system. Using real-time single-molecule imaging, we show that HsRPA or Escherichia coli EcSSB restricts HsEXOI excision activity on nicked or gapped DNA. HsMSH2-HsMSH6 activates HsEXOI by overcoming HsRPA/EcSSB inhibition and exploits multiple dynamic sliding clamps to increase tract length. Conversely, HsMLH1-HsPMS2 regulates tract length by controlling the number of excision complexes, providing a link to 5' MMR.
Collapse
|
40
|
Schmidt TT, Hombauer H. Visualization of mismatch repair complexes using fluorescence microscopy. DNA Repair (Amst) 2016; 38:58-67. [DOI: 10.1016/j.dnarep.2015.11.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 09/30/2015] [Accepted: 11/30/2015] [Indexed: 11/15/2022]
|
41
|
Hingorani MM. Mismatch binding, ADP-ATP exchange and intramolecular signaling during mismatch repair. DNA Repair (Amst) 2016; 38:24-31. [PMID: 26704427 PMCID: PMC4740199 DOI: 10.1016/j.dnarep.2015.11.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Revised: 09/08/2015] [Accepted: 11/30/2015] [Indexed: 12/16/2022]
Abstract
The focus of this article is on the DNA binding and ATPase activities of the mismatch repair (MMR) protein, MutS-our current understanding of how this protein uses ATP to fuel its actions on DNA and initiate repair via interactions with MutL, the next protein in the pathway. Structure-function and kinetic studies have yielded detailed views of the MutS mechanism of action in MMR. How MutS and MutL work together after mismatch recognition to enable strand-specific nicking, which leads to strand excision and synthesis, is less clear and remains an active area of investigation.
Collapse
|
42
|
Gauer J, LeBlanc S, Hao P, Qiu R, Case B, Sakato M, Hingorani M, Erie D, Weninger K. Single-Molecule FRET to Measure Conformational Dynamics of DNA Mismatch Repair Proteins. Methods Enzymol 2016; 581:285-315. [PMID: 27793283 PMCID: PMC5423442 DOI: 10.1016/bs.mie.2016.08.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Single-molecule FRET measurements have a unique sensitivity to protein conformational dynamics. The FRET signals can either be interpreted quantitatively to provide estimates of absolute distance in a molecule configuration or can be qualitatively interpreted as distinct states, from which quantitative kinetic schemes for conformational transitions can be deduced. Here we describe methods utilizing single-molecule FRET to reveal the conformational dynamics of the proteins responsible for DNA mismatch repair. Experimental details about the proteins, DNA substrates, fluorescent labeling, and data analysis are included. The complementarity of single molecule and ensemble kinetic methods is discussed as well.
Collapse
Affiliation(s)
- J.W. Gauer
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - S. LeBlanc
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - P. Hao
- North Carolina State University, Raleigh, NC, United States
| | - R. Qiu
- North Carolina State University, Raleigh, NC, United States
| | - B.C. Case
- Wesleyan University, Middletown, CT, United States
| | - M. Sakato
- Wesleyan University, Middletown, CT, United States
| | | | - D.A. Erie
- University of North Carolina at Chapel Hill, Chapel Hill, NC, United States,Corresponding authors: ;
| | - K.R. Weninger
- North Carolina State University, Raleigh, NC, United States,Corresponding authors: ;
| |
Collapse
|
43
|
Friedhoff P, Li P, Gotthardt J. Protein-protein interactions in DNA mismatch repair. DNA Repair (Amst) 2015; 38:50-57. [PMID: 26725162 DOI: 10.1016/j.dnarep.2015.11.013] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 11/11/2015] [Accepted: 11/30/2015] [Indexed: 11/25/2022]
Abstract
The principal DNA mismatch repair proteins MutS and MutL are versatile enzymes that couple DNA mismatch or damage recognition to other cellular processes. Besides interaction with their DNA substrates this involves transient interactions with other proteins which is triggered by the DNA mismatch or damage and controlled by conformational changes. Both MutS and MutL proteins have ATPase activity, which adds another level to control their activity and interactions with DNA substrates and other proteins. Here we focus on the protein-protein interactions, protein interaction sites and the different levels of structural knowledge about the protein complexes formed with MutS and MutL during the mismatch repair reaction.
Collapse
Affiliation(s)
- Peter Friedhoff
- Institute for Biochemistry FB 08, Justus Liebig University, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany.
| | - Pingping Li
- Institute for Biochemistry FB 08, Justus Liebig University, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany
| | - Julia Gotthardt
- Institute for Biochemistry FB 08, Justus Liebig University, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany
| |
Collapse
|
44
|
Groothuizen FS, Sixma TK. The conserved molecular machinery in DNA mismatch repair enzyme structures. DNA Repair (Amst) 2015; 38:14-23. [PMID: 26796427 DOI: 10.1016/j.dnarep.2015.11.012] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 10/05/2015] [Accepted: 11/30/2015] [Indexed: 12/25/2022]
Abstract
The machinery of DNA mismatch repair enzymes is highly conserved in evolution. The process is initiated by recognition of a DNA mismatch, and validated by ATP and the presence of a processivity clamp or a methylation mark. Several events in MMR promote conformational changes that lead to progression of the repair process. Here we discuss functional conformational changes in the MMR proteins and we compare the enzymes to paralogs in other systems.
Collapse
Affiliation(s)
- Flora S Groothuizen
- Division of Biochemistry and CGC.nl, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Titia K Sixma
- Division of Biochemistry and CGC.nl, Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
| |
Collapse
|