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Lafuente-Barquero J, Svejstrup JQ, Luna R, Aguilera A. Expression of human RECQL5 in Saccharomyces cerevisiae causes transcription defects and transcription-associated genome instability. Mol Genet Genomics 2024; 299:59. [PMID: 38796829 PMCID: PMC11128410 DOI: 10.1007/s00438-024-02152-3] [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: 11/21/2023] [Accepted: 05/13/2024] [Indexed: 05/29/2024]
Abstract
RECQL5 is a member of the conserved RecQ family of DNA helicases involved in the maintenance of genome stability that is specifically found in higher eukaryotes and associates with the elongating RNA polymerase II. To expand our understanding of its function we expressed human RECQL5 in the yeast Saccharomyces cerevisiae, which does not have a RECQL5 ortholog. We found that RECQL5 expression leads to cell growth inhibition, increased genotoxic sensitivity and transcription-associated hyperrecombination. Chromatin immunoprecipitation and transcriptomic analysis of yeast cells expressing human RECQL5 shows that this is recruited to transcribed genes and although it causes only a weak impact on gene expression, in particular at G + C-rich genes, it leads to a transcription termination defect detected as readthrough transcription. The data indicate that the interaction between RNAPII and RECQL5 is conserved from yeast to humans. Unexpectedly, however, the RECQL5-ID mutant, previously shown to have reduced the association with RNAPII in vitro, associates with the transcribing polymerase in cells. As a result, expression of RECQL5-ID leads to similar although weaker phenotypes than wild-type RECQL5 that could be transcription-mediated. Altogether, the data suggests that RECQL5 has the intrinsic ability to function in transcription-dependent and independent genome dynamics in S. cerevisiae.
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Affiliation(s)
- Juan Lafuente-Barquero
- Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, 41092, Seville, Spain
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012, Seville, Spain
| | - Jesper Q Svejstrup
- University of Copenhagen, Copenhagen, Denmark
- Francis Crick Institute, London, UK
| | - Rosa Luna
- Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, 41092, Seville, Spain.
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012, Seville, Spain.
| | - Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, 41092, Seville, Spain
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012, Seville, Spain
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2
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Ueno M. Exploring Genetic Interactions with Telomere Protection Gene pot1 in Fission Yeast. Biomolecules 2023; 13:biom13020370. [PMID: 36830739 PMCID: PMC9953254 DOI: 10.3390/biom13020370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Revised: 02/13/2023] [Accepted: 02/14/2023] [Indexed: 02/18/2023] Open
Abstract
The regulation of telomere length has a significant impact on cancer risk and aging in humans. Circular chromosomes are found in humans and are often unstable during mitosis, resulting in genome instability. Some types of cancer have a high frequency of a circular chromosome. Fission yeast is a good model for studying the formation and stability of circular chromosomes as deletion of pot1 (encoding a telomere protection protein) results in rapid telomere degradation and chromosome fusion. Pot1 binds to single-stranded telomere DNA and is conserved from fission yeast to humans. Loss of pot1 leads to viable strains in which all three fission yeast chromosomes become circular. In this review, I will introduce pot1 genetic interactions as these inform on processes such as the degradation of uncapped telomeres, chromosome fusion, and maintenance of circular chromosomes. Therefore, exploring genes that genetically interact with pot1 contributes to finding new genes and/or new functions of genes related to the maintenance of telomeres and/or circular chromosomes.
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Affiliation(s)
- Masaru Ueno
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima 739-8530, Japan; ; Tel.: +81-82-424-7768
- Hiroshima Research Center for Healthy Aging (HiHA), Hiroshima University, Higashi-Hiroshima 739-8530, Japan
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3
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Firlej M, Weir JR. Unwinding during stressful times: Mechanisms of helicases in meiotic recombination. Curr Top Dev Biol 2022; 151:191-215. [PMID: 36681470 DOI: 10.1016/bs.ctdb.2022.06.004] [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: 01/25/2023]
Abstract
Successful meiosis I requires that homologous chromosomes be correctly linked before they are segregated. In most organisms this physical linkage is achieved through the generation of crossovers between the homologs. Meiotic recombination co-opts and modifies the canonical homologous recombination pathway to successfully generate crossovers One of the central components of this pathway are a number of conserved DNA helicases. Helicases couple nucleic acid binding to nucleotide hydrolysis and use this activity to modify DNA or protein-DNA substrates. During meiosis I it is necessary for the cell to modulate the canonical DNA repair pathways in order to facilitate the generation of interhomolog crossovers. Many of these meiotic modulations take place in pathways involving DNA helicases, or with a meiosis specific helicase. This short review explores what is currently understood about these helicases, their interaction partners, and the role of regulatory modifications during meiosis I. We focus in particular on the molecular structure and mechanisms of these helicases.
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Affiliation(s)
- Magdalena Firlej
- Structural Biochemistry of Meiosis Group, Friedrich Miescher Laboratory of the Max Planck Society, Tuebingen, Germany
| | - John R Weir
- Structural Biochemistry of Meiosis Group, Friedrich Miescher Laboratory of the Max Planck Society, Tuebingen, Germany.
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4
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Abstract
The double-helical structure of genomic DNA is both elegant and functional in that it serves both to protect vulnerable DNA bases and to facilitate DNA replication and compaction. However, these design advantages come at the cost of having to evolve and maintain a cellular machinery that can manipulate a long polymeric molecule that readily becomes topologically entangled whenever it has to be opened for translation, replication, or repair. If such a machinery fails to eliminate detrimental topological entanglements, utilization of the information stored in the DNA double helix is compromised. As a consequence, the use of B-form DNA as the carrier of genetic information must have co-evolved with a means to manipulate its complex topology. This duty is performed by DNA topoisomerases, which therefore are, unsurprisingly, ubiquitous in all kingdoms of life. In this review, we focus on how DNA topoisomerases catalyze their impressive range of DNA-conjuring tricks, with a particular emphasis on DNA topoisomerase III (TOP3). Once thought to be the most unremarkable of topoisomerases, the many lives of these type IA topoisomerases are now being progressively revealed. This research interest is driven by a realization that their substrate versatility and their ability to engage in intimate collaborations with translocases and other DNA-processing enzymes are far more extensive and impressive than was thought hitherto. This, coupled with the recent associations of TOP3s with developmental and neurological pathologies in humans, is clearly making us reconsider their undeserved reputation as being unexceptional enzymes.
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Affiliation(s)
- Anna H Bizard
- Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
| | - Ian D Hickson
- Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
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5
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Davé A, Pai CC, Durley SC, Hulme L, Sarkar S, Wee BY, Prudden J, Tinline-Purvis H, Cullen JK, Walker C, Watson A, Carr AM, Murray JM, Humphrey TC. Homologous recombination repair intermediates promote efficient de novo telomere addition at DNA double-strand breaks. Nucleic Acids Res 2020; 48:1271-1284. [PMID: 31828313 PMCID: PMC7026635 DOI: 10.1093/nar/gkz1109] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 10/23/2019] [Accepted: 12/03/2019] [Indexed: 12/11/2022] Open
Abstract
The healing of broken chromosomes by de novo telomere addition, while a normal developmental process in some organisms, has the potential to cause extensive loss of heterozygosity, genetic disease, or cell death. However, it is unclear how de novo telomere addition (dnTA) is regulated at DNA double-strand breaks (DSBs). Here, using a non-essential minichromosome in fission yeast, we identify roles for the HR factors Rqh1 helicase, in concert with Rad55, in suppressing dnTA at or near a DSB. We find the frequency of dnTA in rqh1Δ rad55Δ cells is reduced following loss of Exo1, Swi5 or Rad51. Strikingly, in the absence of the distal homologous chromosome arm dnTA is further increased, with nearly half of the breaks being healed in rqh1Δ rad55Δ or rqh1Δ exo1Δ cells. These findings provide new insights into the genetic context of highly efficient dnTA within HR intermediates, and how such events are normally suppressed to maintain genome stability.
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Affiliation(s)
- Anoushka Davé
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Sussex BN1 9RQ, UK
| | - Chen-Chun Pai
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
| | - Samuel C Durley
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Sussex BN1 9RQ, UK
| | - Lydia Hulme
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
| | - Sovan Sarkar
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
| | - Boon-Yu Wee
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
| | - John Prudden
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
| | - Helen Tinline-Purvis
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
| | - Jason K Cullen
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
- QIMR Berghofer Medical Research Institute, Brisbane 4006, Australia
| | - Carol Walker
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
| | - Adam Watson
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Sussex BN1 9RQ, UK
| | - Antony M Carr
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Sussex BN1 9RQ, UK
| | - Johanne M Murray
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Sussex BN1 9RQ, UK
| | - Timothy C Humphrey
- CRUK/MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
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6
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Gupta SV, Schmidt KH. Maintenance of Yeast Genome Integrity by RecQ Family DNA Helicases. Genes (Basel) 2020; 11:E205. [PMID: 32085395 PMCID: PMC7074392 DOI: 10.3390/genes11020205] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 02/11/2020] [Accepted: 02/14/2020] [Indexed: 12/28/2022] Open
Abstract
With roles in DNA repair, recombination, replication and transcription, members of the RecQ DNA helicase family maintain genome integrity from bacteria to mammals. Mutations in human RecQ helicases BLM, WRN and RecQL4 cause incurable disorders characterized by genome instability, increased cancer predisposition and premature adult-onset aging. Yeast cells lacking the RecQ helicase Sgs1 share many of the cellular defects of human cells lacking BLM, including hypersensitivity to DNA damaging agents and replication stress, shortened lifespan, genome instability and mitotic hyper-recombination, making them invaluable model systems for elucidating eukaryotic RecQ helicase function. Yeast and human RecQ helicases have common DNA substrates and domain structures and share similar physical interaction partners. Here, we review the major cellular functions of the yeast RecQ helicases Sgs1 of Saccharomyces cerevisiae and Rqh1 of Schizosaccharomyces pombe and provide an outlook on some of the outstanding questions in the field.
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Affiliation(s)
- Sonia Vidushi Gupta
- Department of Cell Biology, Microbiology and Molecular Biology, University of South, Florida, Tampa, FL 33620, USA;
| | - Kristina Hildegard Schmidt
- Department of Cell Biology, Microbiology and Molecular Biology, University of South, Florida, Tampa, FL 33620, USA;
- Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center and Research, Institute, Tampa, FL 33612, USA
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7
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Affiliation(s)
- Giovanni Capranico
- Department
of Pharmacy and Biotechnology, University of Bologna, Via Belmeloro
8/2, 40126 Bologna, Italy
| | - Jessica Marinello
- Department
of Pharmacy and Biotechnology, University of Bologna, Via Belmeloro
8/2, 40126 Bologna, Italy
| | - Giovanni Chillemi
- SCAI
SuperComputing Applications and Innovation Department, Cineca, Via dei Tizii 6, 00185 Rome, Italy
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8
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Kennedy JA, Daughdrill GW, Schmidt KH. A transient α-helical molecular recognition element in the disordered N-terminus of the Sgs1 helicase is critical for chromosome stability and binding of Top3/Rmi1. Nucleic Acids Res 2013; 41:10215-27. [PMID: 24038467 PMCID: PMC3905885 DOI: 10.1093/nar/gkt817] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The RecQ-like DNA helicase family is essential for the maintenance of genome stability in all organisms. Sgs1, a member of this family in Saccharomyces cerevisiae, regulates early and late steps of double-strand break repair by homologous recombination. Using nuclear magnetic resonance spectroscopy, we show that the N-terminal 125 residues of Sgs1 are disordered and contain a transient α-helix that extends from residue 25 to 38. Based on the residue-specific knowledge of transient secondary structure, we designed proline mutations to disrupt this α-helix and observed hypersensitivity to DNA damaging agents and increased frequency of genome rearrangements. In vitro binding assays show that the defects of the proline mutants are the result of impaired binding of Top3 and Rmi1 to Sgs1. Extending mutagenesis N-terminally revealed a second functionally critical region that spans residues 9–17. Depending on the position of the proline substitution in the helix functional impairment of Sgs1 function varied, gradually increasing from the C- to the N-terminus. The multiscale approach we used to interrogate structure/function relationships in the long disordered N-terminal segment of Sgs1 allowed us to precisely define a functionally critical region and should be generally applicable to other disordered proteins.
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Affiliation(s)
- Jessica A. Kennedy
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL 33620, USA, Center for Drug Discovery and Innovation, University of South Florida, Tampa, FL 33612, USA and Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA
| | - Gary W. Daughdrill
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL 33620, USA, Center for Drug Discovery and Innovation, University of South Florida, Tampa, FL 33612, USA and Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA
| | - Kristina H. Schmidt
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL 33620, USA, Center for Drug Discovery and Innovation, University of South Florida, Tampa, FL 33612, USA and Cancer Biology and Evolution Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA
- *To whom correspondence should be addressed. Tel: +1 813 974 1592; Fax: +1 813 974 1614;
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9
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Fission yeast RecQ helicase Rqh1 is required for the maintenance of circular chromosomes. Mol Cell Biol 2013; 33:1175-87. [PMID: 23297345 DOI: 10.1128/mcb.01713-12] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Protection of telomeres protein 1 (Pot1) binds to single-stranded telomere overhangs and protects chromosome ends. RecQ helicases regulate homologous recombination at multiple stages, including resection, strand displacement, and resolution. Fission yeast pot1 and RecQ helicase rqh1 double mutants are synthetically lethal, but the mechanism is not fully understood. Here, we show that the synthetic lethality of pot1Δ rqh1Δ double mutants is due to inappropriate homologous recombination, as it is suppressed by the deletion of rad51(+). The expression of Rad51 in the pot1Δ rqh1Δ rad51Δ triple mutant, which has circular chromosomes, is lethal. Reduction of the expression of Rqh1 in a pot1 disruptant with circular chromosomes caused chromosome missegregation, and this defect was partially suppressed by the deletion of rad51(+). Taken together, our results suggest that Rqh1 is required for the maintenance of circular chromosomes when homologous recombination is active. Crossovers between circular monomeric chromosomes generate dimers that cannot segregate properly in Escherichia coli. We propose that Rqh1 inhibits crossovers between circular monomeric chromosomes to suppress the generation of circular dimers.
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10
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Larsen NB, Hickson ID. RecQ Helicases: Conserved Guardians of Genomic Integrity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 767:161-84. [PMID: 23161011 DOI: 10.1007/978-1-4614-5037-5_8] [Citation(s) in RCA: 129] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
The RecQ family of DNA helicases is highly conserved throughout -evolution, and is important for the maintenance of genome stability. In humans, five RecQ family members have been identified: BLM, WRN, RECQ4, RECQ1 and RECQ5. Defects in three of these give rise to Bloom's syndrome (BLM), Werner's syndrome (WRN) and Rothmund-Thomson/RAPADILINO/Baller-Gerold (RECQ4) syndromes. These syndromes are characterised by cancer predisposition and/or premature ageing. In this review, we focus on the roles of BLM and its S. cerevisiae homologue, Sgs1, in genome maintenance. BLM/Sgs1 has been shown to play a critical role in homologous recombination at multiple steps, including end-resection, displacement loop formation, branch migration and double Holliday junction dissolution. In addition, recent evidence has revealed a role for BLM/Sgs1 in the stabilisation and repair of replication forks damaged during a perturbed S-phase. Finally BLM also plays a role in the suppression and/or resolution of ultra-fine anaphase DNA bridges that form between sister-chromatids during mitosis.
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Affiliation(s)
- Nicolai Balle Larsen
- Nordea Center for Healthy Ageing, Department of Cellular and Molecular Medicine, University of Copenhagen, 2200N, Copenhagen, Denmark
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11
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Krejci L, Altmannova V, Spirek M, Zhao X. Homologous recombination and its regulation. Nucleic Acids Res 2012; 40:5795-818. [PMID: 22467216 PMCID: PMC3401455 DOI: 10.1093/nar/gks270] [Citation(s) in RCA: 448] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Homologous recombination (HR) is critical both for repairing DNA lesions in mitosis and for chromosomal pairing and exchange during meiosis. However, some forms of HR can also lead to undesirable DNA rearrangements. Multiple regulatory mechanisms have evolved to ensure that HR takes place at the right time, place and manner. Several of these impinge on the control of Rad51 nucleofilaments that play a central role in HR. Some factors promote the formation of these structures while others lead to their disassembly or the use of alternative repair pathways. In this article, we review these mechanisms in both mitotic and meiotic environments and in different eukaryotic taxa, with an emphasis on yeast and mammal systems. Since mutations in several proteins that regulate Rad51 nucleofilaments are associated with cancer and cancer-prone syndromes, we discuss how understanding their functions can lead to the development of better tools for cancer diagnosis and therapy.
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Affiliation(s)
- Lumir Krejci
- Department of Biology, Masaryk University, Brno, Czech Republic.
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12
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Amunugama R, Fishel R. Homologous Recombination in Eukaryotes. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 110:155-206. [DOI: 10.1016/b978-0-12-387665-2.00007-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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13
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RecQ helicases; at the crossroad of genome replication, repair, and recombination. Mol Biol Rep 2011; 39:4527-43. [PMID: 21947842 DOI: 10.1007/s11033-011-1243-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 09/14/2011] [Indexed: 01/07/2023]
Abstract
DNA helicases are ubiquitous enzymes that unwind double-stranded DNA in an ATP-dependent and directionally specific manner. Such an action is essential for the processes of DNA repair, recombination, transcription, and DNA replication. Here, I focus on a subgroup of DNA helicases, the RecQ family, which is highly conserved in evolution. Members of this conserved family of proteins have a key role in protecting and stabilizing the genome against deleterious changes. Deficiencies in RecQ helicases can lead to high levels of genomic instability and, in humans, to premature aging and increased susceptibility to cancer. Their diverse roles in DNA metabolism, which include a role in telomere maintenance, reflect interactions with multiple cellular proteins, some of which are multifunctional and also have very diverse functions. In this review, protein structural motifs and the roles of different domains will be discussed first. The Review moves on to speculate about the different models to explain why RecQ helicases are required to protect against genome instability.
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Abstract
The RecQ helicases are conserved from bacteria to humans and play a critical role in genome stability. In humans, loss of RecQ gene function is associated with cancer predisposition and/or premature aging. Recent experiments have shown that the RecQ helicases function during distinct steps during DNA repair; DNA end resection, displacement-loop (D-loop) processing, branch migration, and resolution of double Holliday junctions (dHJs). RecQ function in these different processing steps has important implications for its role in repair of double-strand breaks (DSBs) that occur during DNA replication and meiosis, as well as at specific genomic loci such as telomeres.
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Affiliation(s)
- Kara A Bernstein
- Columbia University Medical Center, Department of Genetics & Development, New York, New York 10032, USA.
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15
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Abstract
Mutations in the highly conserved RecQ helicase, BLM, cause the rare cancer predisposition disorder, Bloom's syndrome. The orthologues of BLM in Saccharomyces cerevisiae and Schizosaccharomyces pombe are SGS1 and rqh1(+), respectively. Studies in these yeast species have revealed a plethora of roles for the Sgs1 and Rqh1 proteins in repair of double strand breaks, restart of stalled replication forks, processing of aberrant intermediates that arise during meiotic recombination, and maintenance of telomeres. In this review, we focus on the known roles of Sgs1 and Rqh1 and how studies in yeast species have improved our knowledge of how BLM suppresses neoplastic transformation.
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Affiliation(s)
- Thomas M Ashton
- Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DS, UK
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16
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Cromie GA, Hyppa RW, Smith GR. The fission yeast BLM homolog Rqh1 promotes meiotic recombination. Genetics 2008; 179:1157-67. [PMID: 18562672 PMCID: PMC2475723 DOI: 10.1534/genetics.108.088955] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Accepted: 03/31/2008] [Indexed: 01/04/2023] Open
Abstract
RecQ helicases are found in organisms as diverse as bacteria, fungi, and mammals. These proteins promote genome stability, and mutations affecting human RecQ proteins underlie premature aging and cancer predisposition syndromes, including Bloom syndrome, caused by mutations affecting the BLM protein. In this study we show that mutants lacking the Rqh1 protein of the fission yeast Schizosaccharomyces pombe, a RecQ and BLM homolog, have substantially reduced meiotic recombination, both gene conversions and crossovers. The relative proportion of gene conversions having associated crossovers is unchanged from that in wild type. In rqh1 mutants, meiotic DNA double-strand breaks are formed and disappear with wild-type frequency and kinetics, and spore viability is only moderately reduced. Genetic analyses and the wild-type frequency of both intersister and interhomolog joint molecules argue against these phenotypes being explained by an increase in intersister recombination at the expense of interhomolog recombination. We suggest that Rqh1 extends hybrid DNA and biases the recombination outcome toward crossing over. Our results contrast dramatically with those from the budding yeast ortholog, Sgs1, which has a meiotic antirecombination function that suppresses recombination events involving more than two DNA duplexes. These observations underscore the multiple recombination functions of RecQ homologs and emphasize that even conserved proteins can be adapted to play different roles in different organisms.
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Affiliation(s)
- Gareth A Cromie
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA
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17
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Two closely related RecQ helicases have antagonistic roles in homologous recombination and DNA repair in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2007; 104:18836-41. [PMID: 18000056 DOI: 10.1073/pnas.0705998104] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
RecQ helicases are involved in the processing of DNA structures arising during replication, recombination, and repair throughout all kingdoms of life. Mutations of different RecQ homologues are responsible for severe human diseases, such as Blooms (BLM) or Werner (WRN) syndrome. The loss of RecQ function is often accompanied by hyperrecombination caused by a lack of crossover suppression. In the Arabidopsis genome seven different RecQ genes are present. Two of them (AtRECQ4A and 4B) arose because of a recent duplication and are still nearly 70% identical on a protein level. Knockout of these genes leads to antagonistic phenotypes: the RECQ4A mutant shows sensitivity to DNA-damaging agents, enhanced homologous recombination (HR) and lethality in a mus81 background. Moreover, mutation of RECQ4A partially suppresses the lethal phenotype of an AtTOP3alpha mutant, a phenomenon that had previously been demonstrated for RecQ homologues of unicellular eukaryotes only. Together, these facts strongly suggest that in plants RECQ4A is functionally equivalent to SGS1 of Saccharomyces cerevisiae and the mammalian BLM protein. In stark contrast, mutants of the closely related RECQ4B are not mutagen-sensitive, not viable in a mus81 background, and unable to suppress the induced lethality caused by loss of TOP3alpha. Moreover, they are strongly impaired in HR. Thus, AtRECQ4B is specifically required to promote but not to suppress crossovers, a role in which it differs from all eukaryotic RecQ homologues known.
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18
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Davies SL, North PS, Hickson ID. Role for BLM in replication-fork restart and suppression of origin firing after replicative stress. Nat Struct Mol Biol 2007; 14:677-9. [PMID: 17603497 DOI: 10.1038/nsmb1267] [Citation(s) in RCA: 184] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Accepted: 06/06/2007] [Indexed: 11/09/2022]
Abstract
Mutations in BLM give rise to Bloom's syndrome, a genetic disorder associated with cancer predisposition and chromosomal instability. Using a dual-labeling system in isolated chromosome fibers, we show that the BLM protein is required for two aspects of the cellular response to replicative stress: efficient replication-fork restart and suppression of new origin firing. These functions require the helicase activity of BLM and the Thr99 residue targeted by stress-activated kinases.
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Affiliation(s)
- Sally L Davies
- Cancer Research UK Laboratories, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
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Raji H, Hartsuiker E. Double-strand break repair and homologous recombination in Schizosaccharomyces pombe. Yeast 2007; 23:963-76. [PMID: 17072889 DOI: 10.1002/yea.1414] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The study of double-strand break repair and homologous recombination in Saccharomyces cerevisiae meiosis has provided important information about the mechanisms involved. However, it has become clear that the resulting recombination models are only partially applicable to repair in mitotic cells, where crossover formation is suppressed. In recent years our understanding of double-strand break repair and homologous recombination in Schizosaccharomyces pombe has increased significantly, and the identification of novel pathways and genes with homologues in higher eukaryotes has increased its value as a model organism for double-strand break repair. In this review we will focus on the involvement of homologous recombination and repair in different aspects of genome stability in Sz. pombe meiosis, replication and telomere maintenance. We will also discuss anti-recombination pathways (that suppress crossover formation), non-homologous end-joining, single-strand annealing and factors that influence the choice and prevalence of the different repair pathways in Sz. pombe.
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Affiliation(s)
- Hayatu Raji
- Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, UK
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Forterre P, Gribaldo S, Gadelle D, Serre MC. Origin and evolution of DNA topoisomerases. Biochimie 2007; 89:427-46. [PMID: 17293019 DOI: 10.1016/j.biochi.2006.12.009] [Citation(s) in RCA: 248] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Accepted: 12/12/2006] [Indexed: 12/28/2022]
Abstract
The DNA topoisomerases are essential for DNA replication, transcription, recombination, as well as for chromosome compaction and segregation. They may have appeared early during the formation of the modern DNA world. Several families and subfamilies of the two types of DNA topoisomerases (I and II) have been described in the three cellular domains of life (Archaea, Bacteria and Eukarya), as well as in viruses infecting eukaryotes or bacteria. The main families of DNA topoisomerases, Topo IA, Topo IB, Topo IC (Topo V), Topo IIA and Topo IIB (Topo VI) are not homologous, indicating that they originated independently. However, some of them share homologous modules or subunits that were probably recruited independently to produce different topoisomerase activities. The puzzling phylogenetic distribution of the various DNA topoisomerase families and subfamilies cannot be easily reconciled with the classical models of early evolution describing the relationships between the three cellular domains. A possible scenario is based on a Last Universal Common Ancestor (LUCA) with a RNA genome (i.e. without the need for DNA topoisomerases). Different families of DNA topoisomerases (some of them possibly of viral origin) would then have been independently introduced in the different cellular domains. We review here the main characteristics of the different families and subfamilies of DNA topoisomerases in a historical and evolutionary perspective, with the hope to stimulate further works and discussions on the origin and evolution of these fascinating enzymes.
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Affiliation(s)
- Patrick Forterre
- Institut de Génétique et Microbiologie, UMR8621, Université Paris-Sud 11, Bat. 400-409, 91405 Orsay Cedex, France
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Viard T, de la Tour CB. Type IA topoisomerases: a simple puzzle? Biochimie 2006; 89:456-67. [PMID: 17141394 DOI: 10.1016/j.biochi.2006.10.013] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2006] [Accepted: 10/20/2006] [Indexed: 11/30/2022]
Abstract
Type IA topoisomerases are enzymes that can modify DNA topology. They form a distinct family of proteins present in all domains of life, from bacteria to archaea and higher eukaryotes. They are composed of two domains: a core domain containing all the conserved motifs involved in the trans-esterification reactions, and a carboxyl-terminal domain that is highly variable in size and sequence. The latter appears to interact with other proteins, defining the physiological use of the topoisomerase activity. The evolutionary relevance of this topoisomerase-cofactor complex, also known as the "toposome", as well as its enzymatic consequences are discussed in this review.
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Affiliation(s)
- Thierry Viard
- Nicholas Cozzarelli Laboratory, Molecular and Cell Biology Department, 16 Barker Hall, University of California, Berkeley, CA 94720-3204, USA.
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Abstract
RecQ DNA helicases function during DNA replication and are essential for the maintenance of genome stability. There is increasing evidence that spontaneous genomic instability occurs primarily during DNA replication, and that proteins involved in the S-phase checkpoint are a principal defence against such instability. Cells that lack functional RecQ helicases exhibit phenotypes consistent with an inability to fully resume replication fork progress after encountering DNA damage or fork arrest. In this review we will concentrate on the various functions of RecQ helicases during S phase in model organisms.
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Affiliation(s)
- Jennifer A Cobb
- Frontiers in Genetics NCCR Program, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva 4, Switzerland.
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Mankouri HW, Hickson ID. Top3 processes recombination intermediates and modulates checkpoint activity after DNA damage. Mol Biol Cell 2006; 17:4473-83. [PMID: 16899506 PMCID: PMC1635375 DOI: 10.1091/mbc.e06-06-0516] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Mutation of TOP3 in Saccharomyces cerevisiae causes poor growth, hyperrecombination, and a failure to fully activate DNA damage checkpoints in S phase. Here, we report that overexpression of a dominant-negative allele of TOP3, TOP3(Y356F), which lacks the catalytic (decatenation) activity of Top3, causes impaired S-phase progression and the persistence of abnormal DNA structures (X-shaped DNA molecules) after exposure to methylmethanesulfonate. The impaired S-phase progression is due to a persistent checkpoint-mediated cell cycle delay and can be overridden by addition of caffeine. Hence, the catalytic activity of Top3 is not required for DNA damage checkpoint activation, but it is required for normal S-phase progression after DNA damage. We also present evidence that the checkpoint-mediated cell cycle delay and persistence of X-shaped DNA molecules resulting from overexpression of TOP3(Y356F) are downstream of Rad51 function. We propose that Top3 functions in S phase to both process homologous recombination intermediates and modulate checkpoint activity.
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Affiliation(s)
- Hocine W. Mankouri
- Cancer Research UK Laboratories, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom
| | - Ian D. Hickson
- Cancer Research UK Laboratories, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom
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Current awareness on yeast. Yeast 2005. [DOI: 10.1002/yea.1169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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