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Murakami-Sekimata A, Sekimata M, Sato N, Hayasaka Y, Nakano A. Deletion of PIN4 Suppresses the Protein Transport Defects Caused by sec12-4 Mutation in Saccharomyces cerevisiae. Microb Physiol 2020; 30:25-35. [PMID: 32958726 DOI: 10.1159/000509633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 06/24/2020] [Indexed: 11/19/2022]
Abstract
Newly synthesized secretory proteins are released into the lumen of the endoplasmic reticulum (ER). The secretory proteins are surrounded by coat protein complex II (COPII) vesicles, and transported from the ER and reach their destinations through the Golgi apparatus. Sec12p is a guanine nucleotide exchange factor for Sar1p, which initiates COPII vesicle budding from the ER. The activation of Sar1p by Sec12p and the subsequent COPII coat assembly have been well characterized, but the events that take place upstream of Sec12p remain unclear. In this study, we isolated the novel extragenic suppressor of sec12-4, PIN4/MDT1, a cell cycle checkpoint target. A yeast two-hybrid screening was used to identify Pin4/Mdt1p as a binding partner of the casein kinase I isoform Hrr25p, which we have previously identified as a modulator of Sec12p function. Deletion of PIN4 suppressed both defects of temperature-sensitive growth and the partial protein transport observed in sec12-4 mutants. The results of this study suggest that Pin4p provides novel aspects of Sec12p modulations.
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Affiliation(s)
- Akiko Murakami-Sekimata
- Division of Theoretical Nursing and Genetics, Graduate School of Medical Science, Yamagata University Faculty of Medicine, Yamagata, Japan,
| | - Masayuki Sekimata
- Radioisotope Research Center, School of Medicine, Fukushima Medical University, Fukushima, Japan
| | - Natsumi Sato
- Division of Theoretical Nursing and Genetics, Graduate School of Medical Science, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Yuto Hayasaka
- Division of Theoretical Nursing and Genetics, Graduate School of Medical Science, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Akihiko Nakano
- Live Cell Super-Resolution Imaging Research Team, Extreme Photonics Research Group, RIKEN Center for Advanced Photonics, Wako, Japan
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2
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Upregulation of dNTP Levels After Telomerase Inactivation Influences Telomerase-Independent Telomere Maintenance Pathway Choice in Saccharomyces cerevisiae. G3-GENES GENOMES GENETICS 2018; 8:2551-2558. [PMID: 29848621 PMCID: PMC6071591 DOI: 10.1534/g3.118.200280] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In 10–15% of cancers, telomere length is maintained by a telomerase-independent, recombination-mediated pathway called alternative lengthening of telomeres (ALT). ALT mechanisms were first seen, and have been best studied, in telomerase-null Saccharomyces cerevisiae cells called “survivors”. There are two main types of survivors. Type I survivors amplify Y′ subtelomeric elements while type II survivors, similar to the majority of human ALT cells, amplify the terminal telomeric repeats. Both types of survivors require Rad52, a key homologous recombination protein, and Pol32, a non-essential subunit of DNA polymerase δ. A number of additional proteins have been reported to be important for either type I or type II survivor formation, but it is still unclear how these two pathways maintain telomeres. In this study, we performed a genome-wide screen to identify novel genes that are important for the formation of type II ALT-like survivors. We identified 23 genes that disrupt type II survivor formation when deleted. 17 of these genes had not been previously reported to do so. Several of these genes (DUN1, CCR4, and MOT2) are known to be involved in the regulation of dNTP levels. We find that dNTP levels are elevated early after telomerase inactivation and that this increase favors the formation of type II survivors.
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Wu Z, Liu J, Zhang QD, Lv DK, Wu NF, Zhou JQ. Rad6-Bre1-mediated H2B ubiquitination regulates telomere replication by promoting telomere-end resection. Nucleic Acids Res 2017; 45:3308-3322. [PMID: 28180293 PMCID: PMC5389628 DOI: 10.1093/nar/gkx101] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 02/08/2017] [Indexed: 12/20/2022] Open
Abstract
Rad6 and Bre1, ubiquitin-conjugating E2 and E3 enzymes respectively, are responsible for histone H2B lysine 123 mono-ubiquitination (H2Bub1) in Saccharomyces cerevisiae. Previous studies have shown that Rad6 and Bre1 regulate telomere length and recombination. However, the underlying molecular mechanism remains largely unknown. Here we report that H2BK123 mutation results in telomere shortening, while inactivation of Ubp8 and/or Ubp10, deubiquitinases of H2Bub1, leads to telomere lengthening in Rad6–Bre1-dependent manner. In telomerase-deficient cells, inactivation of Rad6–Bre1 pathway retards telomere shortening rate and the onset of senescence, while deletion of UBP8 and/or UBP10 accelerates senescence. Thus, Rad6–Bre1 pathway regulates both telomere length and recombination through its role in H2Bub1. Additionally, inactivation of both Rad6–Bre1–H2Bub1 and Mre11–Rad50–Xrs2 (MRX) pathways causes synthetic growth defects and telomere shortening in telomerase-proficient cells, and significantly accelerates senescence and eliminates type II telomere recombination in telomerase-deficient cells. Furthermore, RAD6 or BRE1 deletion, or H2BK123R mutation decreases the accumulation of ssDNA at telomere ends. These results support the model that Rad6–Bre1–H2Bub1 cooperates with MRX to promote telomere-end resection and thus positively regulates both telomerase- and recombination-dependent telomere replication. This study provides a mechanistic link between histone H2B ubiquitination and telomere replication.
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Affiliation(s)
- Zhenfang Wu
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Innovation Center for Cell Signaling Network, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Jun Liu
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Innovation Center for Cell Signaling Network, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Qiong-Di Zhang
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Innovation Center for Cell Signaling Network, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - De-Kang Lv
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Innovation Center for Cell Signaling Network, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Nian-Feng Wu
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Innovation Center for Cell Signaling Network, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China
| | - Jin-Qiu Zhou
- The State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Innovation Center for Cell Signaling Network, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China.,School of Life Science and Technology, Shanghai Tech University, 100 Haike Road, Shanghai 201210, China
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Wade BO, Liu HW, Samora CP, Uhlmann F, Singleton MR. Structural studies of RFC Ctf18 reveal a novel chromatin recruitment role for Dcc1. EMBO Rep 2017; 18:558-568. [PMID: 28188145 PMCID: PMC5376975 DOI: 10.15252/embr.201642825] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 01/05/2017] [Accepted: 01/09/2017] [Indexed: 11/10/2022] Open
Abstract
Replication factor C complexes load and unload processivity clamps from DNA and are involved in multiple DNA replication and repair pathways. The RFCCtf18 variant complex is required for activation of the intra-S-phase checkpoint at stalled replication forks and aids the establishment of sister chromatid cohesion. Unlike other RFC complexes, RFCCtf18 contains two non-Rfc subunits, Dcc1 and Ctf8. Here, we present the crystal structure of the Dcc1-Ctf8 heterodimer bound to the C-terminus of Ctf18. We find that the C-terminus of Dcc1 contains three-winged helix domains, which bind to both ssDNA and dsDNA We further show that these domains are required for full recruitment of the complex to chromatin, and correct activation of the replication checkpoint. These findings provide the first structural data on a eukaryotic seven-subunit clamp loader and define a new biochemical activity for Dcc1.
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Affiliation(s)
- Benjamin O Wade
- Structural Biology of Chromosome Segregation Laboratory, The Francis Crick Institute, London, UK
| | - Hon Wing Liu
- Chromosome Segregation Laboratory, The Francis Crick Institute, London, UK
| | - Catarina P Samora
- Chromosome Segregation Laboratory, The Francis Crick Institute, London, UK
| | - Frank Uhlmann
- Chromosome Segregation Laboratory, The Francis Crick Institute, London, UK
| | - Martin R Singleton
- Structural Biology of Chromosome Segregation Laboratory, The Francis Crick Institute, London, UK
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Abstract
The ends of linear chromosomes are capped by nucleoprotein structures called telomeres. A dysfunctional telomere may resemble a DNA double-strand break (DSB), which is a severe form of DNA damage. The presence of one DSB is sufficient to drive cell cycle arrest and cell death. Therefore cells have evolved mechanisms to repair DSBs such as homologous recombination (HR). HR-mediated repair of telomeres can lead to genome instability, a hallmark of cancer cells, which is why such repair is normally inhibited. However, some HR-mediated processes are required for proper telomere function. The need for some recombination activities at telomeres but not others necessitates careful and complex regulation, defects in which can lead to catastrophic consequences. Furthermore, some cell types can maintain telomeres via telomerase-independent, recombination-mediated mechanisms. In humans, these mechanisms are called alternative lengthening of telomeres (ALT) and are used in a subset of human cancer cells. In this review, we summarize the different recombination activities occurring at telomeres and discuss how they are regulated. Much of the current knowledge is derived from work using yeast models, which is the focus of this review, but relevant studies in mammals are also included.
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Affiliation(s)
- Clémence Claussin
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Michael Chang
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
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Gao H, Moss DL, Parke C, Tatum D, Lustig AJ. The Ctf18RFC clamp loader is essential for telomere stability in telomerase-negative and mre11 mutant alleles. PLoS One 2014; 9:e88633. [PMID: 24533124 PMCID: PMC3923045 DOI: 10.1371/journal.pone.0088633] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Accepted: 01/13/2014] [Indexed: 11/19/2022] Open
Abstract
The function of the replication clamp loaders in the semi-conservative telomere replication and their relationship to telomerase- and recombination mechanisms of telomere addition remains ambiguous. We have investigated the variant clamp loader Ctf18 RFC (Replication Factor C). To understand the role of Ctf18 at the telomere, we first investigated genetic interactions after loss of Ctf18 and TLC1 (the yeast telomerase RNA). We find that the tlc1Δ ctf18Δ double mutant confers a rapid >1000-fold decrease in viability. The rate of loss was similar to the kinetics of cell death in rad52Δ tlc1Δ cells. However, the Ctf18 pathway is distinct from Rad52, required for the repair of DSBs, as demonstrated by the synthetic lethality of rad52▵ tlc1Δ ctf18Δ triple mutants. These data suggest that each mutant elicits non-redundant defects acting on the same substrate. Second, interactions of the yeast hyper-recombinational mutant, mre11A470T, with ctf18▵ confer a synergistic cold sensitivity. The phenotype of these double mutants ultimately results in telomere loss and the generation of recombinational survivors. We observed a similar synergism between single mutants that led to hypersensitivity to the DNA alkylating agent, methane methyl sulphonate (MMS), the replication fork inhibitor hydroxyurea (HU), and to a failure to separate telomeres of sister chromatids. Hence, ctf18Δ and mre11A470T act in different pathways on telomere substrates for multiple phenotypes. The mre11A470T cells also displayed a DNA damage response (DDR) at 15°C but not at 30°C while ctf18Δ mutants conferred a constitutive DDR activity. Both the 15°C DDR pattern and growth rate were reversible at 30°C and displayed telomerase activity in vivo. We hypothesize that Ctf18 confers protection against stalling and/or breaks at the replication fork in cells that either lack, or are compromised for, telomerase activity. This Ctf18-based function is likely to contribute another level to telomere size homeostasis.
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Affiliation(s)
- Honghai Gao
- Department of Biochemistry and Molecular Biology, Tulane University Medical Center, New Orleans, Louisiana, United States of America
| | - Daniel L. Moss
- Department of Biochemistry and Molecular Biology, Tulane University Medical Center, New Orleans, Louisiana, United States of America
| | - Courtney Parke
- Department of Biochemistry and Molecular Biology, Tulane University Medical Center, New Orleans, Louisiana, United States of America
| | - Danielle Tatum
- Department of Biochemistry and Molecular Biology, Tulane University Medical Center, New Orleans, Louisiana, United States of America
| | - Arthur J. Lustig
- Department of Biochemistry and Molecular Biology, Tulane University Medical Center, New Orleans, Louisiana, United States of America
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Yeast hEST1A/B (SMG5/6)-like proteins contribute to environment-sensing adaptive gene expression responses. G3-GENES GENOMES GENETICS 2013; 3:1649-59. [PMID: 23893744 PMCID: PMC3789790 DOI: 10.1534/g3.113.006924] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
During its natural life cycle, budding yeast (Saccharomyces cerevisiae) has to adapt to drastically changing environments, but how environmental-sensing pathways are linked to adaptive gene expression changes remains incompletely understood. Here, we describe two closely related yeast hEST1A-B (SMG5-6)–like proteins termed Esl1 and Esl2 that contain a 14-3-3–like domain and a putative PilT N-terminus ribonuclease domain. We found that, unlike their metazoan orthologs, Esl1 and Esl2 were not involved in nonsense-mediated mRNA decay or telomere maintenance pathways. However, in genome-wide expression array analyses, absence of Esl1 and Esl2 led to more than two-fold deregulation of ∼50 transcripts, most of which were expressed inversely to the appropriate metabolic response to environmental nutrient supply; for instance, normally glucose-repressed genes were derepressed in esl1Δ esl2Δ double mutants during growth in a high-glucose environment. Likewise, in a genome-wide synthetic gene array screen, esl1Δ esl2Δ double mutants were synthetic sick with null mutations for Rim8 and Dfg16, which form the environmental-sensing complex of the Rim101 pH response gene expression pathway. Overall, these results suggest that Esl1 and Esl2 contribute to the regulation of adaptive gene expression responses of environmental sensing pathways.
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8
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Molecular basis of the essential s phase function of the rad53 checkpoint kinase. Mol Cell Biol 2013; 33:3202-13. [PMID: 23754745 DOI: 10.1128/mcb.00474-13] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The essential yeast kinases Mec1 and Rad53, or human ATR and Chk1, are crucial for checkpoint responses to exogenous genotoxic agents, but why they are also required for DNA replication in unperturbed cells remains poorly understood. Here we report that even in the absence of DNA-damaging agents, the rad53-4AQ mutant, lacking the N-terminal Mec1 phosphorylation site cluster, is synthetic lethal with a deletion of the RAD9 DNA damage checkpoint adaptor. This phenotype is caused by an inability of rad53-4AQ to activate the downstream kinase Dun1, which then leads to reduced basal deoxynucleoside triphosphate (dNTP) levels, spontaneous replication fork stalling, and constitutive activation of and dependence on S phase DNA damage checkpoints. Surprisingly, the kinase-deficient rad53-K227A mutant does not share these phenotypes but is rendered inviable by additional phosphosite mutations that prevent its binding to Dun1. The results demonstrate that ultralow Rad53 catalytic activity is sufficient for normal replication of undamaged chromosomes as long as it is targeted toward activation of the effector kinase Dun1. Our findings indicate that the essential S phase function of Rad53 is comprised by the combination of its role in regulating basal dNTP levels and its compensatory kinase function if dNTP levels are perturbed.
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Suppression of chromosome healing and anticheckpoint pathways in yeast postsenescence survivors. Genetics 2013; 194:403-8. [PMID: 23535383 DOI: 10.1534/genetics.113.150813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Telomere repeat-like sequences at DNA double-strand breaks (DSBs) inhibit DNA damage signaling and serve as seeds to convert DSBs to new telomeres in mutagenic chromosome healing pathways. We find here that the response to seed-containing DSBs differs fundamentally between budding yeast (Saccharomyces cerevisiae) cells that maintain their telomeres via telomerase and so-called postsenescence survivors that use recombination-based alternative lengthening of telomere (ALT) mechanisms. Whereas telomere seeds are efficiently elongated by telomerase, they remain remarkably stable without de novo telomerization or extensive end resection in telomerase-deficient (est2Δ, tlc1Δ) postsenescence survivors. This telomere seed hyper-stability in ALT cells is associated with, but not caused by, prolonged DNA damage checkpoint activity (RAD9, RAD53) compared to telomerase-positive cells or presenescent telomerase-negative cells. The results indicate that both chromosome healing and anticheckpoint activity of telomere seeds are suppressed in yeast models of ALT pathways.
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Hu Y, Tang HB, Liu NN, Tong XJ, Dang W, Duan YM, Fu XH, Zhang Y, Peng J, Meng FL, Zhou JQ. Telomerase-null survivor screening identifies novel telomere recombination regulators. PLoS Genet 2013; 9:e1003208. [PMID: 23390378 PMCID: PMC3547846 DOI: 10.1371/journal.pgen.1003208] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 11/12/2012] [Indexed: 01/17/2023] Open
Abstract
Telomeres are protein–DNA structures found at the ends of linear chromosomes and are crucial for genome integrity. Telomeric DNA length is primarily maintained by the enzyme telomerase. Cells lacking telomerase will undergo senescence when telomeres become critically short. In Saccharomyces cerevisiae, a very small percentage of cells lacking telomerase can remain viable by lengthening telomeres via two distinct homologous recombination pathways. These “survivor” cells are classified as either Type I or Type II, with each class of survivor possessing distinct telomeric DNA structures and genetic requirements. To elucidate the regulatory pathways contributing to survivor generation, we knocked out the telomerase RNA gene TLC1 in 280 telomere-length-maintenance (TLM) gene mutants and examined telomere structures in post-senescent survivors. We uncovered new functional roles for 10 genes that affect the emerging ratio of Type I versus Type II survivors and 22 genes that are required for Type II survivor generation. We further verified that Pif1 helicase was required for Type I recombination and that the INO80 chromatin remodeling complex greatly affected the emerging frequency of Type I survivors. Finally, we found the Rad6-mediated ubiquitination pathway and the KEOPS complex were required for Type II recombination. Our data provide an independent line of evidence supporting the idea that these genes play important roles in telomere dynamics. Homologous recombination is a means for an organism or a cell to repair damaged DNA in its genome. Eukaryotic chromosomes have a linear configuration with two ends that are special DNA–protein structures called telomeres. Telomeres can be recognized by the cell as DNA double-strand breaks and subjected to repair by homologous recombination. In the baker's yeast Saccharomyces cerevisiae, cells that lack the enzyme telomerase, which is the primary factor responsible for telomeric DNA elongation, are able to escape senescence and cell death when telomeres undergo repair via homologous recombination. In this study, we have performed genetic screens to identify genes that affect telomeric DNA recombination. By examining the telomere structures in 280 mutants, each of which lacks both a telomere-length-maintenance gene and telomerase RNA gene, we identified 32 genes that were not previously known to be involved in telomere recombination. These genes have functions in a variety of cellular processes, and our work provides new insights into the regulation of telomere recombination in the absence of telomerase.
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Affiliation(s)
- Yan Hu
- The State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Hong-Bo Tang
- The State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Ning-Ning Liu
- The State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Xia-Jing Tong
- The State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Wei Dang
- The State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Yi-Min Duan
- The State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Xiao-Hong Fu
- The State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Yang Zhang
- The State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Jing Peng
- The State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Fei-Long Meng
- The State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
| | - Jin-Qiu Zhou
- The State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
- * E-mail:
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Cosnier B, Kwapisz M, Hatin I, Namy O, Denmat SHL, Morillon A, Rousset JP, Fabret C. A viable hypomorphic allele of the essential IMP3 gene reveals novel protein functions in Saccharomyces cerevisiae. PLoS One 2011; 6:e19500. [PMID: 21559332 PMCID: PMC3084874 DOI: 10.1371/journal.pone.0019500] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Accepted: 04/06/2011] [Indexed: 12/31/2022] Open
Abstract
In Saccharomyces cerevisiae, the essential IMP3 gene encodes a component of the SSU processome, a large ribonucleoprotein complex required for processing of small ribosomal subunit RNA precursors. Mutation of the IMP3 termination codon to a sense codon resulted in a viable mutant allele producing a C-terminal elongated form of the Imp3 protein. A strain expressing the mutant allele displayed ribosome biogenesis defects equivalent to IMP3 depletion. This hypomorphic allele represented a unique opportunity to investigate and better understand the Imp3p functions. We demonstrated that the +1 frameshifting was increased in the mutant strain. Further characterizations revealed involvement of the Imp3 protein in DNA repair and telomere length control, pointing to a functional relationship between both pathways and ribosome biogenesis.
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Affiliation(s)
- Bruno Cosnier
- IGM, CNRS, UMR 8621, Orsay, France
- Université Paris-Sud, Orsay, France
| | | | - Isabelle Hatin
- IGM, CNRS, UMR 8621, Orsay, France
- Université Paris-Sud, Orsay, France
| | - Olivier Namy
- IGM, CNRS, UMR 8621, Orsay, France
- Université Paris-Sud, Orsay, France
| | | | | | | | - Céline Fabret
- IGM, CNRS, UMR 8621, Orsay, France
- Université Pierre et Marie Curie, Paris, France
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12
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Traven A, Lo TL, Pike BL, Friesen H, Guzzo J, Andrews B, Heierhorst J. Dual functions of Mdt1 in genome maintenance and cell integrity pathways in Saccharomyces cerevisiae. Yeast 2010; 27:41-52. [PMID: 19894211 DOI: 10.1002/yea.1730] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Recent evidence indicates considerable cross-talk between genome maintenance and cell integrity control pathways. The RNA recognition motif (RRM)- and SQ/TQ cluster domain (SCD)-containing protein Mdt1 is required for repair of 3'-blocked DNA double-strand breaks (DSBs) and efficient recombinational maintenance of telomeres in budding yeast. Here we show that deletion of MDT1 (PIN4/YBL051C) leads to severe synthetic sickness in the absence of the genes for the central cell integrity MAP kinases Bck1 and Slt2/Mpk1. Consistent with a cell integrity function, mdt1Delta cells are hypersensitive to the cell wall toxin calcofluor white and the Bck1-Slt2 pathway activator caffeine. An RRM-deficient mdt1-RRM0 allele shares the severe bleomycin hypersensitivity, inefficient recombinational telomere maintenance and slt2 synthetic sickness phenotypes, but not the cell wall toxin hypersensitivity with mdt1Delta. However, the mdt1-RRM(3A) allele, where only the RNA-binding site is mutated, behaves similarly to the wild-type, suggesting that the Mdt1 RRM functions as a protein-protein interaction rather than a nucleic acid-binding module. Surprisingly, in a strain background where double mutants are sick but still viable, bck1Deltamdt1Delta and slt2Deltamdt1Delta mutants differ in some of their phenotypes, consistent with the emerging concept of flexible signal entry and exit points in the Bck1-Mkk1/2-Slt2 pathway. Overall, the results indicate that Mdt1 has partially separable functions in both cell wall and genome integrity pathways.
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Affiliation(s)
- Ana Traven
- St. Vincent's Institute of Medical Research and Department of Medicine SVH, University of Melbourne, Fitzroy, Victoria 3065, Australia
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13
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Lin YH, Chang CC, Wong CW, Teng SC. Recruitment of Rad51 and Rad52 to short telomeres triggers a Mec1-mediated hypersensitivity to double-stranded DNA breaks in senescent budding yeast. PLoS One 2009; 4:e8224. [PMID: 20011546 PMCID: PMC2790616 DOI: 10.1371/journal.pone.0008224] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2009] [Accepted: 11/16/2009] [Indexed: 01/05/2023] Open
Abstract
Telomere maintenance is required for chromosome stability, and telomeres are typically replicated by the action of telomerase. In both mammalian tumor and yeast cells that lack telomerase, telomeres are maintained by an alternative recombination mechanism. Here we demonstrated that the budding yeast Saccharomyces cerevisiae type I survivors derived from telomerase-deficient cells were hypersensitive to DNA damaging agents. Assays to track telomere lengths and drug sensitivity of telomerase-deficient cells from spore colonies to survivors suggested a correlation between telomere shortening and bleomycin sensitivity. Our genetic studies demonstrated that this sensitivity depends on Mec1, which signals checkpoint activation, leading to prolonged cell-cycle arrest in senescent budding yeasts. Moreover, we also observed that when cells equipped with short telomeres, recruitments of homologous recombination proteins, Rad51 and Rad52, were reduced at an HO-endonuclease-catalyzed double-strand break (DSB), while their associations were increased at chromosome ends. These results suggested that the sensitive phenotype may be attributed to the sequestration of repair proteins to compromised telomeres, thus limiting the repair capacity at bona fide DSB sites.
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Affiliation(s)
- Yi-Hsuan Lin
- Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chia-Ching Chang
- Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chui-Wei Wong
- Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Shu-Chun Teng
- Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
- * E-mail:
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14
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Current awareness on yeast. Yeast 2008. [DOI: 10.1002/yea.1459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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