51
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Roy JCL, Vitalo A, Andrew MA, Mota-Silva E, Kovalenko M, Burch Z, Nhu AM, Cohen PE, Grabczyk E, Wheeler VC, Mouro Pinto R. Somatic CAG expansion in Huntington's disease is dependent on the MLH3 endonuclease domain, which can be excluded via splice redirection. Nucleic Acids Res 2021; 49:3907-3918. [PMID: 33751106 PMCID: PMC8053082 DOI: 10.1093/nar/gkab152] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 02/19/2021] [Accepted: 02/23/2021] [Indexed: 11/18/2022] Open
Abstract
Somatic expansion of the CAG repeat tract that causes Huntington's disease (HD) is thought to contribute to the rate of disease pathogenesis. Therefore, factors influencing repeat expansion are potential therapeutic targets. Genes in the DNA mismatch repair pathway are critical drivers of somatic expansion in HD mouse models. Here, we have tested, using genetic and pharmacological approaches, the role of the endonuclease domain of the mismatch repair protein MLH3 in somatic CAG expansion in HD mice and patient cells. A point mutation in the MLH3 endonuclease domain completely eliminated CAG expansion in the brain and peripheral tissues of a HD knock-in mouse model (HttQ111). To test whether the MLH3 endonuclease could be manipulated pharmacologically, we delivered splice switching oligonucleotides in mice to redirect Mlh3 splicing to exclude the endonuclease domain. Splice redirection to an isoform lacking the endonuclease domain was associated with reduced CAG expansion. Finally, CAG expansion in HD patient-derived primary fibroblasts was also significantly reduced by redirecting MLH3 splicing to the endogenous endonuclease domain-lacking isoform. These data indicate the potential of targeting the MLH3 endonuclease domain to slow somatic CAG repeat expansion in HD, a therapeutic strategy that may be applicable across multiple repeat expansion disorders.
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Affiliation(s)
- Jennie C L Roy
- Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Antonia Vitalo
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Marissa A Andrew
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Eduarda Mota-Silva
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Marina Kovalenko
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Zoe Burch
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Anh M Nhu
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Paula E Cohen
- Department of Biomedical Sciences, Cornell University, Ithaca, NY 14853, USA.,Center for Reproductive Genomics, Cornell University, Ithaca, NY 14853, USA
| | - Ed Grabczyk
- Department of Genetics, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
| | - Vanessa C Wheeler
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Ricardo Mouro Pinto
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA 02114, USA.,Department of Neurology, Harvard Medical School, Boston, MA 02115, USA.,Program in Medical and Population Genetics, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
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52
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Shukla V, Høffding MK, Hoffmann ER. Genome diversity and instability in human germ cells and preimplantation embryos. Semin Cell Dev Biol 2021; 113:132-147. [PMID: 33500205 PMCID: PMC8097364 DOI: 10.1016/j.semcdb.2020.12.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 12/18/2020] [Indexed: 12/26/2022]
Abstract
Genome diversity is essential for evolution and is of fundamental importance to human health. Generating genome diversity requires phases of DNA damage and repair that can cause genome instability. Humans have a high incidence of de novo congenital disorders compared to other organisms. Recent access to eggs, sperm and preimplantation embryos is revealing unprecedented rates of genome instability that may result in infertility and de novo mutations that cause genomic imbalance in at least 70% of conceptions. The error type and incidence of de novo mutations differ during developmental stages and are influenced by differences in male and female meiosis. In females, DNA repair is a critical factor that determines fertility and reproductive lifespan. In males, aberrant meiotic recombination causes infertility, embryonic failure and pregnancy loss. Evidence suggest germ cells are remarkably diverse in the type of genome instability that they display and the DNA damage responses they deploy. Additionally, the initial embryonic cell cycles are characterized by a high degree of genome instability that cause congenital disorders and may limit the use of CRISPR-Cas9 for heritable genome editing.
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Affiliation(s)
- Vallari Shukla
- DNRF Center for Chromosome Stability, Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Miya Kudo Høffding
- DNRF Center for Chromosome Stability, Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Eva R Hoffmann
- DNRF Center for Chromosome Stability, Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
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53
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Gray S, Santiago ER, Chappie JS, Cohen PE. Cyclin N-Terminal Domain-Containing-1 Coordinates Meiotic Crossover Formation with Cell-Cycle Progression in a Cyclin-Independent Manner. Cell Rep 2021; 32:107858. [PMID: 32640224 PMCID: PMC7341696 DOI: 10.1016/j.celrep.2020.107858] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 05/14/2020] [Accepted: 06/12/2020] [Indexed: 01/01/2023] Open
Abstract
During mammalian meiotic prophase I, programmed DNA double-strand breaks are repaired by non-crossover or crossover events, the latter predominantly occurring via the class I crossover pathway and requiring the cyclin N-terminal domain-containing 1(CNTD1) protein. Using an epitope-tagged Cntd1 allele, we detect a short isoform of CNTD1 in vivo that lacks a predicted N-terminal cyclin domain and does not bind cyclin-dependent kinases. Instead, we find that the short-form CNTD1 variant associates with components of the replication factor C (RFC) machinery to facilitate crossover formation, and with the E2 ubiquitin conjugating enzyme, CDC34, to regulate ubiquitylation and subsequent degradation of the WEE1 kinase, thereby modulating cell-cycle progression. We propose that these interactions facilitate a role for CNTD1 as a stop-go regulator during prophase I, ensuring accurate and complete crossover formation before allowing metaphase progression and the first meiotic division. CNTD1 associates with sites of crossing over in meiosis, co-localizing with MutLγ In the testis, CNTD1 does not interact with CDKs or with known crossover regulators CNTD1 regulates crossing over via interactions with the replication factor C complex CNTD1 regulates cell-cycle progression via interactions with the SCF complex
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Affiliation(s)
- Stephen Gray
- Department of Biomedical Sciences and Center for Reproductive Genomics, Cornell University, Ithaca, NY 14853, USA.
| | - Emerson R Santiago
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Joshua S Chappie
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Paula E Cohen
- Department of Biomedical Sciences and Center for Reproductive Genomics, Cornell University, Ithaca, NY 14853, USA.
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54
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Pannafino G, Alani E. Coordinated and Independent Roles for MLH Subunits in DNA Repair. Cells 2021; 10:cells10040948. [PMID: 33923939 PMCID: PMC8074049 DOI: 10.3390/cells10040948] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Revised: 04/15/2021] [Accepted: 04/16/2021] [Indexed: 02/05/2023] Open
Abstract
The MutL family of DNA mismatch repair proteins (MMR) acts to maintain genomic integrity in somatic and meiotic cells. In baker’s yeast, the MutL homolog (MLH) MMR proteins form three heterodimeric complexes, MLH1-PMS1, MLH1-MLH2, and MLH1-MLH3. The recent discovery of human PMS2 (homolog of baker’s yeast PMS1) and MLH3 acting independently of human MLH1 in the repair of somatic double-strand breaks questions the assumption that MLH1 is an obligate subunit for MLH function. Here we provide a summary of the canonical roles for MLH factors in DNA genomic maintenance and in meiotic crossover. We then present the phenotypes of cells lacking specific MLH subunits, particularly in meiotic recombination, and based on this analysis, propose a model for an independent early role for MLH3 in meiosis to promote the accurate segregation of homologous chromosomes in the meiosis I division.
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55
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Rahman MM, Mohiuddin M, Shamima Keka I, Yamada K, Tsuda M, Sasanuma H, Andreani J, Guerois R, Borde V, Charbonnier JB, Takeda S. Genetic evidence for the involvement of mismatch repair proteins, PMS2 and MLH3, in a late step of homologous recombination. J Biol Chem 2021; 295:17460-17475. [PMID: 33453991 DOI: 10.1074/jbc.ra120.013521] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 09/28/2020] [Indexed: 12/15/2022] Open
Abstract
Homologous recombination (HR) repairs DNA double-strand breaks using intact homologous sequences as template DNA. Broken DNA and intact homologous sequences form joint molecules (JMs), including Holliday junctions (HJs), as HR intermediates. HJs are resolved to form crossover and noncrossover products. A mismatch repair factor, MLH3 endonuclease, produces the majority of crossovers during meiotic HR, but it remains elusive whether mismatch repair factors promote HR in nonmeiotic cells. We disrupted genes encoding the MLH3 and PMS2 endonucleases in the human B cell line, TK6, generating null MLH3-/- and PMS2-/- mutant cells. We also inserted point mutations into the endonuclease motif of MLH3 and PMS2 genes, generating endonuclease death MLH3DN/DN and PMS2EK/EK cells. MLH3-/- and MLH3DN/DN cells showed a very similar phenotype, a 2.5-fold decrease in the frequency of heteroallelic HR-dependent repair of restriction enzyme-induced double-strand breaks. PMS2-/- and PMS2EK/EK cells showed a phenotype very similar to that of the MLH3 mutants. These data indicate that MLH3 and PMS2 promote HR as an endonuclease. The MLH3DN/DN and PMS2EK/EK mutations had an additive effect on the heteroallelic HR. MLH3DN/DN/PMS2EK/EK cells showed normal kinetics of γ-irradiation-induced Rad51 foci but a significant delay in the resolution of Rad51 foci and a 3-fold decrease in the number of cisplatin-induced sister chromatid exchanges. The ectopic expression of the Gen1 HJ re-solvase partially reversed the defective heteroallelic HR of MLH3DN/DN/PMS2EK/EK cells. Taken together, we propose that MLH3 and PMS2 promote HR as endonucleases, most likely by processing JMs in mammalian somatic cells.
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Affiliation(s)
- Md Maminur Rahman
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Mohiuddin Mohiuddin
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Islam Shamima Keka
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Kousei Yamada
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Masataka Tsuda
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Hiroyuki Sasanuma
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Jessica Andreani
- Institute for Integrative Biology of the Cell (I2BC), Commissariat à l'Energie Atomique (CEA), CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Raphael Guerois
- Institute for Integrative Biology of the Cell (I2BC), Commissariat à l'Energie Atomique (CEA), CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Valerie Borde
- Institut Curie, CNRS, UMR3244, PSL Research University, Paris, France
| | - Jean-Baptiste Charbonnier
- Institute for Integrative Biology of the Cell (I2BC), Commissariat à l'Energie Atomique (CEA), CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Shunichi Takeda
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
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56
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Osman K, Algopishi U, Higgins JD, Henderson IR, Edwards KJ, Franklin FCH, Sanchez-Moran E. Distal Bias of Meiotic Crossovers in Hexaploid Bread Wheat Reflects Spatio-Temporal Asymmetry of the Meiotic Program. FRONTIERS IN PLANT SCIENCE 2021; 12:631323. [PMID: 33679846 DOI: 10.33892/ffpls.2021.631323] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 01/18/2021] [Indexed: 05/25/2023]
Abstract
Meiotic recombination generates genetic variation and provides physical links between homologous chromosomes (crossovers) essential for accurate segregation. In cereals the distribution of crossovers, cytologically evident as chiasmata, is biased toward the distal regions of chromosomes. This creates a bottleneck for plant breeders in the development of varieties with improved agronomic traits, as genes situated in the interstitial and centromere proximal regions of chromosomes rarely recombine. Recent advances in wheat genomics and genome engineering combined with well-developed wheat cytogenetics offer new opportunities to manipulate recombination and unlock genetic variation. As a basis for these investigations we have carried out a detailed analysis of meiotic progression in hexaploid wheat (Triticum aestivum) using immunolocalization of chromosome axis, synaptonemal complex and recombination proteins. 5-Bromo-2'-deoxyuridine (BrdU) labeling was used to determine the chronology of key events in relation to DNA replication. Axis morphogenesis, synapsis and recombination initiation were found to be spatio-temporally coordinated, beginning in the gene-dense distal chromosomal regions and later occurring in the interstitial/proximal regions. Moreover, meiotic progression in the distal regions was coordinated with the conserved chromatin cycles that are a feature of meiosis. This mirroring of the chiasma bias was also evident in the distribution of the gene-associated histone marks, H3K4me3 and H3K27me3; the repeat-associated mark, H3K27me1; and H3K9me3. We believe that this study provides a cytogenetic framework for functional studies and ongoing initiatives to manipulate recombination in the wheat genome.
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Affiliation(s)
- Kim Osman
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Uthman Algopishi
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - James D Higgins
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
| | - Ian R Henderson
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Keith J Edwards
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
| | - F Chris H Franklin
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
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57
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Bhagwat NR, Owens SN, Ito M, Boinapalli JV, Poa P, Ditzel A, Kopparapu S, Mahalawat M, Davies OR, Collins SR, Johnson JR, Krogan NJ, Hunter N. SUMO is a pervasive regulator of meiosis. eLife 2021; 10:57720. [PMID: 33502312 PMCID: PMC7924959 DOI: 10.7554/elife.57720] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 01/26/2021] [Indexed: 02/06/2023] Open
Abstract
Protein modification by SUMO helps orchestrate the elaborate events of meiosis to faithfully produce haploid gametes. To date, only a handful of meiotic SUMO targets have been identified. Here, we delineate a multidimensional SUMO-modified meiotic proteome in budding yeast, identifying 2747 conjugation sites in 775 targets, and defining their relative levels and dynamics. Modified sites cluster in disordered regions and only a minority match consensus motifs. Target identities and modification dynamics imply that SUMOylation regulates all levels of chromosome organization and each step of meiotic prophase I. Execution-point analysis confirms these inferences, revealing functions for SUMO in S-phase, the initiation of recombination, chromosome synapsis and crossing over. K15-linked SUMO chains become prominent as chromosomes synapse and recombine, consistent with roles in these processes. SUMO also modifies ubiquitin, forming hybrid oligomers with potential to modulate ubiquitin signaling. We conclude that SUMO plays diverse and unanticipated roles in regulating meiotic chromosome metabolism. Most mammalian, yeast and other eukaryote cells have two sets of chromosomes, one from each parent, which contain all the cell’s DNA. Sex cells – like the sperm and egg – however, have half the number of chromosomes and are formed by a specialized type of cell division known as meiosis. At the start of meiosis, each cell replicates its chromosomes so that it has twice the amount of DNA. The cell then undergoes two rounds of division to form sex cells which each contain only one set of chromosomes. Before the cell divides, the two duplicated sets of chromosomes pair up and swap sections of their DNA. This exchange allows each new sex cell to have a unique combination of DNA, resulting in offspring that are genetically distinct from their parents. This complex series of events is tightly regulated, in part, by a protein called the 'small ubiquitin-like modifier' (or SUMO for short), which attaches itself to other proteins and modifies their behavior. This process, known as SUMOylation, can affect a protein’s stability, where it is located in the cell and how it interacts with other proteins. However, despite SUMO being known as a key regulator of meiosis, only a handful of its protein targets have been identified. To gain a better understanding of what SUMO does during meiosis, Bhagwat et al. set out to find which proteins are targeted by SUMO in budding yeast and to map the specific sites of modification. The experiments identified 2,747 different sites on 775 different proteins, suggesting that SUMO regulates all aspects of meiosis. Consistently, inactivating SUMOylation at different times revealed SUMO plays a role at every stage of meiosis, including the replication of DNA and the exchanges between chromosomes. In depth analysis of the targeted proteins also revealed that SUMOylation targets different groups of proteins at different stages of meiosis and interacts with other protein modifications, including the ubiquitin system which tags proteins for destruction. The data gathered by Bhagwat et al. provide a starting point for future research into precisely how SUMO proteins control meiosis in yeast and other organisms. In humans, errors in meiosis are the leading cause of pregnancy loss and congenital diseases. Most of the proteins identified as SUMO targets in budding yeast are also present in humans. So, this research could provide a platform for medical advances in the future. The next step is to study mammalian models, such as mice, to confirm that the regulation of meiosis by SUMO is the same in mammals as in yeast.
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Affiliation(s)
- Nikhil R Bhagwat
- Howard Hughes Medical Institute, University of California Davis, Davis, United States.,Department of Microbiology & Molecular Genetics, University of California Davis, Davis, United States
| | - Shannon N Owens
- Department of Microbiology & Molecular Genetics, University of California Davis, Davis, United States
| | - Masaru Ito
- Howard Hughes Medical Institute, University of California Davis, Davis, United States.,Department of Microbiology & Molecular Genetics, University of California Davis, Davis, United States
| | - Jay V Boinapalli
- Department of Microbiology & Molecular Genetics, University of California Davis, Davis, United States
| | - Philip Poa
- Department of Microbiology & Molecular Genetics, University of California Davis, Davis, United States
| | - Alexander Ditzel
- Department of Microbiology & Molecular Genetics, University of California Davis, Davis, United States
| | - Srujan Kopparapu
- Department of Microbiology & Molecular Genetics, University of California Davis, Davis, United States
| | - Meghan Mahalawat
- Department of Microbiology & Molecular Genetics, University of California Davis, Davis, United States
| | - Owen Richard Davies
- Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne, United Kingdom
| | - Sean R Collins
- Department of Microbiology & Molecular Genetics, University of California Davis, Davis, United States
| | - Jeffrey R Johnson
- Department of Cellular & Molecular Pharmacology, University of California San Francisco, San Francisco, United States
| | - Nevan J Krogan
- Department of Cellular & Molecular Pharmacology, University of California San Francisco, San Francisco, United States
| | - Neil Hunter
- Howard Hughes Medical Institute, University of California Davis, Davis, United States.,Department of Microbiology & Molecular Genetics, University of California Davis, Davis, United States.,Department of Molecular & Cellular Biology, University of California Davis, Davis, United States
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58
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Osman K, Algopishi U, Higgins JD, Henderson IR, Edwards KJ, Franklin FCH, Sanchez-Moran E. Distal Bias of Meiotic Crossovers in Hexaploid Bread Wheat Reflects Spatio-Temporal Asymmetry of the Meiotic Program. FRONTIERS IN PLANT SCIENCE 2021; 12:631323. [PMID: 33679846 PMCID: PMC7928317 DOI: 10.3389/fpls.2021.631323] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 01/18/2021] [Indexed: 05/09/2023]
Abstract
Meiotic recombination generates genetic variation and provides physical links between homologous chromosomes (crossovers) essential for accurate segregation. In cereals the distribution of crossovers, cytologically evident as chiasmata, is biased toward the distal regions of chromosomes. This creates a bottleneck for plant breeders in the development of varieties with improved agronomic traits, as genes situated in the interstitial and centromere proximal regions of chromosomes rarely recombine. Recent advances in wheat genomics and genome engineering combined with well-developed wheat cytogenetics offer new opportunities to manipulate recombination and unlock genetic variation. As a basis for these investigations we have carried out a detailed analysis of meiotic progression in hexaploid wheat (Triticum aestivum) using immunolocalization of chromosome axis, synaptonemal complex and recombination proteins. 5-Bromo-2'-deoxyuridine (BrdU) labeling was used to determine the chronology of key events in relation to DNA replication. Axis morphogenesis, synapsis and recombination initiation were found to be spatio-temporally coordinated, beginning in the gene-dense distal chromosomal regions and later occurring in the interstitial/proximal regions. Moreover, meiotic progression in the distal regions was coordinated with the conserved chromatin cycles that are a feature of meiosis. This mirroring of the chiasma bias was also evident in the distribution of the gene-associated histone marks, H3K4me3 and H3K27me3; the repeat-associated mark, H3K27me1; and H3K9me3. We believe that this study provides a cytogenetic framework for functional studies and ongoing initiatives to manipulate recombination in the wheat genome.
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Affiliation(s)
- Kim Osman
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
- *Correspondence: Kim Osman
| | - Uthman Algopishi
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - James D. Higgins
- Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
| | - Ian R. Henderson
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Keith J. Edwards
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
| | | | - Eugenio Sanchez-Moran
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
- Eugenio Sanchez-Moran
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59
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Machín F. Implications of Metastable Nicks and Nicked Holliday Junctions in Processing Joint Molecules in Mitosis and Meiosis. Genes (Basel) 2020; 11:genes11121498. [PMID: 33322845 PMCID: PMC7763299 DOI: 10.3390/genes11121498] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 11/25/2020] [Accepted: 12/09/2020] [Indexed: 12/13/2022] Open
Abstract
Joint molecules (JMs) are intermediates of homologous recombination (HR). JMs rejoin sister or homolog chromosomes and must be removed timely to allow segregation in anaphase. Current models pinpoint Holliday junctions (HJs) as a central JM. The canonical HJ (cHJ) is a four-way DNA that needs specialized nucleases, a.k.a. resolvases, to resolve into two DNA molecules. Alternatively, a helicase–topoisomerase complex can deal with pairs of cHJs in the dissolution pathway. Aside from cHJs, HJs with a nick at the junction (nicked HJ; nHJ) can be found in vivo and are extremely good substrates for resolvases in vitro. Despite these findings, nHJs have been neglected as intermediates in HR models. Here, I present a conceptual study on the implications of nicks and nHJs in the final steps of HR. I address this from a biophysical, biochemical, topological, and genetic point of view. My conclusion is that they ease the elimination of JMs while giving genetic directionality to the final products. Additionally, I present an alternative view of the dissolution pathway since the nHJ that results from the second end capture predicts a cross-join isomerization. Finally, I propose that this isomerization nicely explains the strict crossover preference observed in synaptonemal-stabilized JMs in meiosis.
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Affiliation(s)
- Félix Machín
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain;
- Instituto de Tecnologías Biomédicas, Universidad de la Laguna, 38200 Tenerife, Spain
- Facultad de Ciencias de la Salud, Universidad Fernando Pessoa Canarias, 35450 Las Palmas de Gran Canaria, Spain
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60
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Exo1 recruits Cdc5 polo kinase to MutLγ to ensure efficient meiotic crossover formation. Proc Natl Acad Sci U S A 2020; 117:30577-30588. [PMID: 33199619 DOI: 10.1073/pnas.2013012117] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Crossovers generated during the repair of programmed meiotic double-strand breaks must be tightly regulated to promote accurate homolog segregation without deleterious outcomes, such as aneuploidy. The Mlh1-Mlh3 (MutLγ) endonuclease complex is critical for crossover resolution, which involves mechanistically unclear interplay between MutLγ and Exo1 and polo kinase Cdc5. Using budding yeast to gain temporal and genetic traction on crossover regulation, we find that MutLγ constitutively interacts with Exo1. Upon commitment to crossover repair, MutLγ-Exo1 associate with recombination intermediates, followed by direct Cdc5 recruitment that triggers MutLγ crossover activity. We propose that Exo1 serves as a central coordinator in this molecular interplay, providing a defined order of interaction that prevents deleterious, premature activation of crossovers. MutLγ associates at a lower frequency near centromeres, indicating that spatial regulation across chromosomal regions reduces risky crossover events. Our data elucidate the temporal and spatial control surrounding a constitutive, potentially harmful, nuclease. We also reveal a critical, noncatalytic role for Exo1, through noncanonical interaction with polo kinase. These mechanisms regulating meiotic crossovers may be conserved across species.
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61
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Furman CM, Elbashir R, Alani E. Expanded roles for the MutL family of DNA mismatch repair proteins. Yeast 2020; 38:39-53. [PMID: 32652606 DOI: 10.1002/yea.3512] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 07/01/2020] [Accepted: 07/08/2020] [Indexed: 12/31/2022] Open
Abstract
The MutL family of DNA mismatch repair proteins plays a critical role in excising and repairing misincorporation errors during DNA replication. In many eukaryotes, members of this family have evolved to modulate and resolve recombination intermediates into crossovers during meiosis. In these organisms, such functions promote the accurate segregation of chromosomes during the meiosis I division. What alterations occurred in MutL homolog (MLH) family members that enabled them to acquire these new roles? In this review, we present evidence that the yeast Mlh1-Mlh3 and Mlh1-Mlh2 complexes have evolved novel enzymatic and nonenzymatic activities and protein-protein interactions that are critical for their meiotic functions. Curiously, even with these changes, these complexes retain backup and accessory roles in DNA mismatch repair during vegetative growth.
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Affiliation(s)
- Christopher M Furman
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
| | - Ryan Elbashir
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
| | - Eric Alani
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY, USA
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