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AMPKα-like proteins as LKB1 downstream targets in cell physiology and cancer. J Mol Med (Berl) 2021; 99:651-662. [PMID: 33661342 DOI: 10.1007/s00109-021-02040-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 12/28/2020] [Accepted: 01/12/2021] [Indexed: 12/13/2022]
Abstract
One of the key events in cancer development is the ability of tumor cells to overcome nutrient deprivation and hypoxia. Among proteins performing metabolic adaptation to the various cellular nutrient conditions, liver kinase B 1 (LKB1) and its main downstream target adenosine monophosphate (AMP)-activated protein kinase α (AMPKα) are important sensors of energy requirements within the cell. Although LKB1 was originally described as a tumor suppressor, given its role in metabolism, it potentially acts as a double-edged sword. AMPKα, a master regulator of cell energy demands, is activated when ATP level drops under a certain threshold, responding accordingly through its downstream targets. Twelve downstream kinase targets of LKB1 have been described as AMPKα-like proteins. This group is comprised of novel (nua) kinase family (NUAK) kinases (NUAK1 and 2) linked to cell cycle progression and ultraviolet (UV)-damage; microtubule affinity regulating kinases (MARKs) (MARK1, MARK2, MARK3, and MARK4) that are involved in cell polarity; salt inducible kinases (SIK) (SIK1, SIK2, also known as Qin-induced kinase or QIK and SIK3) that are implicated in cell metabolism and adipose tissue development and mitotic regulation; maternal embryonic leuzine zipper kinase (MELK) that regulate oocyte maturation; and finally brain selective kinases (BRSKs) (BRSK1 and 2), which have been mainly characterized in the brain due to their role in neuronal polarization. Thus, many efforts have been made in order to harness LKB1 kinase and its downstream targets as a possible therapeutic hub in tumor development and propagation. In this review, we describe LKB1 and its downstream target AMPK summarize major functions of various AMPK-like proteins, while focusing on biological functions of BRSK1 and 2 in different models.
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Lee MS, Joo JW, Choi H, Kang HA, Kim K. Mec1 Modulates Interhomolog Crossover and Interplays with Tel1 at Post Double-Strand Break Stages. J Microbiol Biotechnol 2020; 30:469-475. [PMID: 31847509 PMCID: PMC9728206 DOI: 10.4014/jmb.1909.09020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Revised: 11/27/2019] [Accepted: 12/01/2019] [Indexed: 12/15/2022]
Abstract
During meiosis I, programmed DNA double-strand breaks (DSBs) occur to promote chromosome pairing and recombination between homologs. In Saccharomyces cerevisiae, Mec1 and Tel1, the orthologs of human ATR and ATM, respectively, regulate events upstream of the cell cycle checkpoint to initiate DNA repair. Tel1ATM and Mec1ATR are required for phosphorylating various meiotic proteins during recombination. This study aimed to investigate the role of Tel1ATM and Mec1ATR in meiotic prophase via physical analysis of recombination. Tel1ATM cooperated with Mec1ATR to mediate DSB-to-single end invasion transition, but negatively regulated DSB formation. Furthermore, Mec1ATR was required for the formation of interhomolog joint molecules from early prophase, thus establishing a recombination partner choice. Moreover, Mec1ATR specifically promoted crossover-fated DSB repair. Together, these results suggest that Tel1ATM and Mec1ATR function redundantly or independently in all post-DSB stages.
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Affiliation(s)
- Min-Su Lee
- Department of Life Sciences, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Jung Whan Joo
- Department of Life Sciences, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Hyungseok Choi
- Department of Life Sciences, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Hyun Ah Kang
- Department of Life Sciences, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Keunpil Kim
- Department of Life Sciences, Chung-Ang University, Seoul 06974, Republic of Korea
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The roles of fission yeast exonuclease 5 in nuclear and mitochondrial genome stability. DNA Repair (Amst) 2019; 83:102720. [PMID: 31563844 DOI: 10.1016/j.dnarep.2019.102720] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 09/04/2019] [Accepted: 09/19/2019] [Indexed: 11/22/2022]
Abstract
The Exo5 family consists of bi-directional, single-stranded DNA-specific exonucleases that contain an iron-sulfur cluster as a structural motif and have multiple roles in DNA metabolism. S. cerevisiae Exo5 is essential for mitochondrial genome maintenance, while the human ortholog is important for nuclear genome stability and DNA repair. Here, we identify the Exo5 ortholog in Schizosaccharomyes pombe (spExo5). The activity of spExo5 is highly similar to that of the human enzyme. When the single-stranded DNA is coated with single-stranded DNA binding protein RPA, spExo5 become a 5'-specific exonuclease. Exo5Δ mutants are sensitive to various DNA damaging agents, particularly interstrand crosslinking agents. An epistasis analysis places exo5+ in the Fanconi pathway for interstrand crosslink repair. Exo5+ is in a redundant pathway with rad2+, which encodes the flap endonuclease FEN1, for mitochondrial genome maintenance. Deletion of both genes lead to severe depletion of the mitochondrial genome, and defects in respiration, indicating that either spExo5 or spFEN1 is necessary for mitochondrial DNA metabolism.
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Furuya K, Niki H. Hyphal differentiation induced via a DNA damage checkpoint-dependent pathway engaged in crosstalk with nutrient stress signaling in Schizosaccharomyces japonicus. Curr Genet 2012; 58:291-303. [PMID: 23090706 PMCID: PMC3490063 DOI: 10.1007/s00294-012-0384-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 09/13/2012] [Accepted: 10/05/2012] [Indexed: 12/16/2022]
Abstract
DNA damage response includes DNA repair, nucleotide metabolism and even a control of cell fates including differentiation, cell death pathway or some combination of these. The responses to DNA damage differ from species to species. Here we aim to delineate the checkpoint pathway in the dimorphic fission yeast Schizosaccharomyces japonicus, where DNA damage can trigger a differentiation pathway that is a switch from a bidirectional yeast growth mode to an apical hyphal growth mode, and the switching is regulated via a checkpoint kinase, Chk1. This Chk1-dependent switch to hyphal growth is activated with even low doses of agents that damage DNA; therefore, we reasoned that this switch may depend on other genes orthologous to the components of the classical Sz. pombe Chk1-dependent DNA checkpoint pathway. As an initial test of this hypothesis, we assessed the effects of mutations in Sz. japonicus orthologs of Sz. pombe checkpoint genes on this switch from bidirectional to hyphal growth. The same set of DNA checkpoint genes was confirmed in Sz. japonicus. We tested the effect of each DNA checkpoint mutants on hyphal differentiation by DNA damage. We found that the Sz. japonicus hyphal differentiation pathway was dependent on Sz. japonicus orthologs of Sz. pombe checkpoint genes-(SP)rad3, (SP)rad26, (SP)rad9, (SP)rad1, (SP)rad24, (SP)rad25, (SP)crb2, and (SP)chk1-that function in the DNA damage checkpoint pathway, but was not dependent on orthologs of two Sz. pombe genes-(SP)cds1 or (SP)mrc1-that function in the DNA replication checkpoint pathway. These findings indicated that although the role of each component of the DNA damage checkpoint and DNA replication checkpoint is mostly same between the two fission yeasts, the DNA damage checkpoint was the only pathway that governed DNA damage-dependent hyphal growth. We also examined whether DNA damage checkpoint signaling engaged in functional crosstalk with other hyphal differentiation pathways because hyphal differentiation can also be triggered by nutritional stress. Here, we discovered genetic interactions that indicated that the cAMP pathway engaged in crosstalk with Chk1-dependent signaling.
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Affiliation(s)
- Kanji Furuya
- Department of Genetics, Graduate University for Advanced Studies, Sokendai, Hayama, Miura District, Japan
- Microbial Genetics Laboratory, Genetic Strains Research Center, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka, 411-8540 Japan
- Present Address: Department of Mutagenesis, Radiation Biology Center, Kyoto University, Kyoto, Japan
| | - Hironori Niki
- Department of Genetics, Graduate University for Advanced Studies, Sokendai, Hayama, Miura District, Japan
- Microbial Genetics Laboratory, Genetic Strains Research Center, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka, 411-8540 Japan
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Doerfler L, Harris L, Viebranz E, Schmidt KH. Differential genetic interactions between Sgs1, DNA-damage checkpoint components and DNA repair factors in the maintenance of chromosome stability. Genome Integr 2011; 2:8. [PMID: 22040455 PMCID: PMC3231943 DOI: 10.1186/2041-9414-2-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Accepted: 10/31/2011] [Indexed: 11/21/2022] Open
Abstract
Background Genome instability is associated with human cancers and chromosome breakage syndromes, including Bloom's syndrome, caused by inactivation of BLM helicase. Numerous mutations that lead to genome instability are known, yet how they interact genetically is poorly understood. Results We show that spontaneous translocations that arise by nonallelic homologous recombination in DNA-damage-checkpoint-defective yeast lacking the BLM-related Sgs1 helicase (sgs1Δ mec3Δ) are inhibited if cells lack Mec1/ATR kinase. Tel1/ATM, in contrast, acts as a suppressor independently of Mec3 and Sgs1. Translocations are also inhibited in cells lacking Dun1 kinase, but not in cells defective in a parallel checkpoint branch defined by Chk1 kinase. While we had previously shown that RAD51 deletion did not inhibit translocation formation, RAD59 deletion led to inhibition comparable to the rad52Δ mutation. A candidate screen of other DNA metabolic factors identified Exo1 as a strong suppressor of chromosomal rearrangements in the sgs1Δ mutant, becoming even more important for chromosomal stability upon MEC3 deletion. We determined that the C-terminal third of Exo1, harboring mismatch repair protein binding sites and phosphorylation sites, is dispensable for Exo1's roles in chromosomal rearrangement suppression, mutation avoidance and resistance to DNA-damaging agents. Conclusions Our findings suggest that translocations between related genes can form by Rad59-dependent, Rad51-independent homologous recombination, which is independently suppressed by Sgs1, Tel1, Mec3 and Exo1 but promoted by Dun1 and the telomerase-inhibitor Mec1. We propose a model for the functional interaction between mitotic recombination and the DNA-damage checkpoint in the suppression of chromosomal rearrangements in sgs1Δ cells.
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Affiliation(s)
- Lillian Doerfler
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 E. Fowler Avenue, Tampa, FL 33620, USA
| | - Lorena Harris
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 E. Fowler Avenue, Tampa, FL 33620, USA
| | - Emilie Viebranz
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 E. Fowler Avenue, Tampa, FL 33620, USA
| | - Kristina H Schmidt
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, 4202 E. Fowler Avenue, Tampa, FL 33620, USA
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Purtill FS, Whitehall SK, Williams ES, McInerny CJ, Sharrocks AD, Morgan BA. A homeodomain transcription factor regulates the DNA replication checkpoint in yeast. Cell Cycle 2011; 10:664-70. [PMID: 21304269 DOI: 10.4161/cc.10.4.14824] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Checkpoints monitor the successful completion of cell cycle processes, such as DNA replication, and also regulate the expression of cell cycle-dependent genes that are required for responses. In the model yeast Schizosaccharomyces pombe G 1/S phase-specific gene expression is regulated by the MBF (also known as DSC1) transcription factor complex and is also activated by the mammalian ATM/ATR-related Rad3 DNA replication checkpoint. Here, we show that the Yox1 homeodomain transcription factor acts to co-ordinate the expression of MBF-regulated genes during the cell division cycle. Moreover, our data suggests that Yox1 is inactivated by the Rad3 DNA replication checkpoint via phosphorylation by the conserved Cds1 checkpoint kinase. Collectively, our data has implications for understanding the mechanisms underlying the coordination of cell cycle processes in eukaryotes.
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Affiliation(s)
- Frances S Purtill
- Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle upon tyne, UK
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Dutta C, Rhind N. The role of specific checkpoint-induced S-phase transcripts in resistance to replicative stress. PLoS One 2009; 4:e6944. [PMID: 19750219 PMCID: PMC2735676 DOI: 10.1371/journal.pone.0006944] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Accepted: 08/13/2009] [Indexed: 12/04/2022] Open
Abstract
Checkpoint activation during S phase modulates transcription. In response to replication arrest, the fission yeast Cds1 checkpoint kinase maintains the normal S-phase transcriptional program by regulating MBF, the S-phase transcription factor. We show that similar regulation occurs in response to DNA damage during S-phase. We test the relative contributions to replication-stress resistance of transcriptional regulation and the two other major checkpoint functions: cell-cycle arrest and fork stabilization. We show that, although transcriptional regulation provides only modest resistance relative to fork stabilization, it contributes significantly to cell survival. Finally, we investigate the roles of two specific transcripts: mik1 and mrc1. These results demonstrate the general importance of checkpoint regulation of G1/S transcription in response to replicative stress and elucidate the specific roles of Mik1 and Mrc1 in the checkpoint.
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Affiliation(s)
- Chaitali Dutta
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Nicholas Rhind
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail:
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A Cds1-mediated checkpoint protects the MBF activator Rep2 from ubiquitination by anaphase-promoting complex/cyclosome-Ste9 at S-phase arrest in fission yeast. Mol Cell Biol 2009; 29:4959-70. [PMID: 19596787 DOI: 10.1128/mcb.00562-09] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcription of the MluI cell cycle box (MCB) motif-containing genes at G(1) phase is regulated by the MCB-binding factors (MBF) (also called DSC1) in Schizosaccharomyces pombe. Upon S-phase arrest, the MBF transcriptional activity is induced through the accumulation of the MBF activator Rep2. In this study, we show that the turnover of Rep2 is attributable to ubiquitin-mediated proteolysis. Levels of Rep2 oscillate during the cell cycle, with a peak at G(1) phase, coincident with the MBF activity. Furthermore, we show that Rep2 ubiquitination requires the function of the E3 ligase anaphase-promoting complex/cyclosome (APC/C). Ste9 can be phosphorylated by the checkpoint kinase Cds1 in vitro, and its inhibition/phosphorylation at S-phase arrest is dependent on the function of Cds1. Our data indicate that the Cds1-dependent stabilization of Rep2 is achieved through the inhibition/phosphorylation of APC/C-Ste9 at the onset of S-phase arrest. Stabilization of Rep2 is important for stimulating transcription of the MBF-dependent genes to ensure a sufficient supply of proteins essential for cell recovery from S-phase arrest. We propose that oscillation of Rep2 plays a role in regulation of periodic transcription of the MBF-dependent genes during cell cycle progression.
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9
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Koltovaya NA. Activation of repair and checkpoints by double-strand DNA breaks: Activational cascade of protein phosphorylation. RUSS J GENET+ 2009. [DOI: 10.1134/s1022795409010013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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10
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The DNA replication checkpoint directly regulates MBF-dependent G1/S transcription. Mol Cell Biol 2008; 28:5977-85. [PMID: 18662996 DOI: 10.1128/mcb.00596-08] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The DNA replication checkpoint transcriptionally upregulates genes that allow cells to adapt to and survive replication stress. Our results show that, in the fission yeast Schizosaccharomyces pombe, the replication checkpoint regulates the entire G(1)/S transcriptional program by directly regulating MBF, the G(1)/S transcription factor. Instead of initiating a checkpoint-specific transcriptional program, the replication checkpoint targets MBF to maintain the normal G(1)/S transcriptional program during replication stress. We propose a mechanism for this regulation, based on in vitro phosphorylation of the Cdc10 subunit of MBF by the Cds1 replication-checkpoint kinase. Replacement of two potential phosphorylation sites with phosphomimetic amino acids suffices to promote the checkpoint transcriptional program, suggesting that Cds1 phosphorylation directly regulates MBF-dependent transcription. The conservation of MBF between fission and budding yeast, and recent results implicating MBF as a target of the budding yeast replication checkpoint, suggests that checkpoint regulation of the MBF transcription factor is a conserved strategy for coping with replication stress. Furthermore, the structural and regulatory similarity between MBF and E2F, the metazoan G(1)/S transcription factor, suggests that this checkpoint mechanism may be broadly conserved among eukaryotes.
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11
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Chu Z, Li J, Eshaghi M, Peng X, Karuturi RKM, Liu J. Modulation of cell cycle-specific gene expressions at the onset of S phase arrest contributes to the robust DNA replication checkpoint response in fission yeast. Mol Biol Cell 2007; 18:1756-67. [PMID: 17332498 PMCID: PMC1855038 DOI: 10.1091/mbc.e06-10-0928] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Fission yeast replication checkpoint kinases Rad3p and Cds1p are essential for maintaining cell viability after transient treatment with hydroxyurea (HU), an agent that blocks DNA replication. Although current studies have focused on the cyclin-dependent protein kinase Cdc2p that is regulated by these checkpoint kinases, other aspects of their functions at the onset of S phase arrest have not been fully understood. In this study, we use genome-wide DNA microarray analyses to show that HU-induced change of expression profiles in synchronized G(2) cells occurs specifically at the onset of S phase arrest. Induction of many core environmental stress response genes and repression of ribosomal genes happen during S phase arrest. Significantly, peak expression level of the MluI-like cell cycle box (MCB)-cluster (G(1)) genes is maintained at the onset of S phase arrest in a Rad3p- and Cds1p-dependent manner. Expression level maintenance of the MCB-cluster is mediated through the accumulation of Rep2p, a putative transcriptional activator of the MBF complex. Conversely, the FKH-cluster (M) genes are repressed during the onset of S phase arrest in a Rad3p-dependent manner. Repression of the FKH-cluster genes is mediated through the decreased levels of one of the putative forkhead transcription factors, Sep1p, but not Fkh2p. Together, our results demonstrate that Rad3p and Cds1p modulate transcriptional response during the onset of S phase arrest.
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Affiliation(s)
| | - Juntao Li
- Computational and Mathematical Biology, Genome Institute of Singapore, Singapore 118672; and
| | | | - Xu Peng
- *Biological Investigations and
| | - R. Krishna M. Karuturi
- Computational and Mathematical Biology, Genome Institute of Singapore, Singapore 118672; and
| | - Jianhua Liu
- *Biological Investigations and
- Department of Biochemistry, National University of Singapore, Singapore 117595
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12
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Holmquist GP, Ashley T. Chromosome organization and chromatin modification: influence on genome function and evolution. Cytogenet Genome Res 2006; 114:96-125. [PMID: 16825762 DOI: 10.1159/000093326] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2005] [Accepted: 12/15/2005] [Indexed: 11/19/2022] Open
Abstract
Histone modifications of nucleosomes distinguish euchromatic from heterochromatic chromatin states, distinguish gene regulation in eukaryotes from that of prokaryotes, and appear to allow eukaryotes to focus recombination events on regions of highest gene concentrations. Four additional epigenetic mechanisms that regulate commitment of cell lineages to their differentiated states are involved in the inheritance of differentiated states, e.g., DNA methylation, RNA interference, gene repositioning between interphase compartments, and gene replication time. The number of additional mechanisms used increases with the taxon's somatic complexity. The ability of siRNA transcribed from one locus to target, in trans, RNAi-associated nucleation of heterochromatin in distal, but complementary, loci seems central to orchestration of chromatin states along chromosomes. Most genes are inactive when heterochromatic. However, genes within beta-heterochromatin actually require the heterochromatic state for their activity, a property that uniquely positions such genes as sources of siRNA to target heterochromatinization of both the source locus and distal loci. Vertebrate chromosomes are organized into permanent structures that, during S-phase, regulate simultaneous firing of replicon clusters. The late replicating clusters, seen as G-bands during metaphase and as meiotic chromomeres during meiosis, epitomize an ontological utilization of all five self-reinforcing epigenetic mechanisms to regulate the reversible chromatin state called facultative (conditional) heterochromatin. Alternating euchromatin/heterochromatin domains separated by band boundaries, and interphase repositioning of G-band genes during ontological commitment can impose constraints on both meiotic interactions and mammalian karyotype evolution.
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Affiliation(s)
- G P Holmquist
- Biology Department, City of Hope Medical Center, Duarte, CA, USA.
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13
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McSherry TD, Mueller PR. Xenopus Cds1 is regulated by DNA-dependent protein kinase and ATR during the cell cycle checkpoint response to double-stranded DNA ends. Mol Cell Biol 2004; 24:9968-85. [PMID: 15509799 PMCID: PMC525475 DOI: 10.1128/mcb.24.22.9968-9985.2004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The checkpoint kinase Cds1 (Chk2) plays a key role in cell cycle checkpoint responses with functions in cell cycle arrest, DNA repair, and induction of apoptosis. Proper regulation of Cds1 is essential for appropriate cellular responses to checkpoint-inducing insults. While the kinase ATM has been shown to be important in the regulation of human Cds1 (hCds1), here we report that the kinases ATR and DNA-dependent protein kinase (DNA-PK) play more significant roles in the regulation of Xenopus Cds1 (XCds1). Under normal cell cycle conditions, nonactivated XCds1 constitutively associates with a Xenopus ATR complex. The association of XCds1 with this complex does not require a functional forkhead activation domain but does require a putative SH3 binding region that is found in XCds1. In response to double-stranded DNA ends, the amino terminus of XCds1 is rapidly phosphorylated in a sequential pattern. First DNA-PK phosphorylates serine 39, a site not previously recognized as important in Cds1 regulation. Xenopus ATM, ATR, and/or DNA-PK then phosphorylate three consensus serine/glutamine sites. Together, these phosphorylations have the dual function of inducing dissociation from the ATR complex and independently promoting the full activation of XCds1. Thus, the checkpoint-mediated activation of XCds1 requires phosphorylation by multiple phosphoinositide 3-kinase-related kinases, protein-protein dissociation, and autophosphorylation.
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Affiliation(s)
- Troy D McSherry
- Center for Molecular Oncology, Department of Biochemistry and Molecular Biology, University of Chicago, JFK R318, 924 E. 57th St., Chicago, IL 60637, USA
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14
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Heitzeberg F, Chen IP, Hartung F, Orel N, Angelis KJ, Puchta H. The Rad17 homologue of Arabidopsis is involved in the regulation of DNA damage repair and homologous recombination. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 38:954-68. [PMID: 15165187 DOI: 10.1111/j.1365-313x.2004.02097.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Rad17 is involved in DNA checkpoint control in yeast and human cells. A homologue of this gene as well as other genes of the pathway (the 9-1-1 complex) are present in Arabidopsis and share conserved sequence domains with their yeast and human counterparts. DNA-damaging agents induce AtRAD17 transcriptionally. AtRAD17 mutants show increased sensitivity to the DNA-damaging chemicals bleomycin and mitomycin C (MMC), which can be reversed by complementation, suggesting that the loss of function of Rad17 disturbs DNA repair in plant cells. Our results are further confirmed by the phenotype of a mutant of the 9-1-1 complex (Rad9), which is also sensitive to the same chemicals. AtRAD9 and AtRAD17 seem to be epistatic as the double mutant is not more sensitive to the chemicals than the single mutants. The mutants show a delay in the general repair of double-strand breaks (DSBs). However, frequencies of intrachromosomal homologous recombination (HR) are enhanced. Nevertheless, the mutants are proficient for a further induction of HR by genotoxic stresses. Our results indicate that a mutant Rad17 pathway is associated with a general deregulation of DNA repair, which seems to be correlated with a deficiency in non-homologous DSB repair.
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Affiliation(s)
- Fabian Heitzeberg
- Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, D-06466 Gatersleben, Germany
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15
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Lu R, Niida H, Nakanishi M. Human SAD1 kinase is involved in UV-induced DNA damage checkpoint function. J Biol Chem 2004; 279:31164-70. [PMID: 15150265 DOI: 10.1074/jbc.m404728200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Checkpoint activation by DNA damage during G(2) prevents activation of cyclin B/Cdc2 complexes, and as a consequence, mitotic entry is blocked. Although initiation and maintenance of G(2) arrest are known to be regulated by at least two distinct signaling pathways, including those of p38MAPK and ataxia-telangiectasia-mutated (ATM)- and Rad3-related (ATR)-Chk1 in higher eukaryotes, the actual number of signaling pathways involved in this regulation is still elusive. In the present study, we identified human SAD1 (hsSAD1) by searching a sequence data base. The predicted hsSAD1 protein comprises 778 amino acids and shares significant homology with the fission yeast Cdr2, a mitosis-regulatory kinase, and Caenorhabditis elegans SAD1, a neuronal cell polarity regulator. HsSAD1 transcript was expressed ubiquitously with the highest levels of expression in brain and testis. HsSAD1 specifically phosphorylated Wee1A, Cdc25-C, and -B on Ser-642, Ser-216, and Ser-361 in vitro, respectively. Overexpression of hsSAD1 resulted in an increased phosphorylation of Cdc25C on Ser-216 in vivo. DNA damage induced by UV or methyl methane sulfonate but not by IR enhanced endogenous hsSAD1 kinase activity in a caffeine-sensitive manner and caused translocation of its protein from cytoplasm to nucleus. Overexpression of wild-type hsSAD1 induced G(2)/M arrest in HeLa S2 cells. Furthermore, UV-induced G(2)/M arrest was partially abrogated by the reduced expression of hsSAD1 using small interfering RNA. These results suggest that hsSAD1 acts as checkpoint kinase upon DNA damage induced by UV or methyl methane sulfonate. The identification of this new kinase suggests the existence of an alternative checkpoint pathway other than those of ATR-Chk1 and p38MAPK.
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Affiliation(s)
- Rui Lu
- Department of Biochemistry and Cell Biology, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan
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Lottersberger F, Rubert F, Baldo V, Lucchini G, Longhese MP. Functions of Saccharomyces cerevisiae 14-3-3 Proteins in Response to DNA Damage and to DNA Replication Stress. Genetics 2003; 165:1717-32. [PMID: 14704161 PMCID: PMC1462906 DOI: 10.1093/genetics/165.4.1717] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Two members of the 14-3-3 protein family, involved in key biological processes in different eukaryotes, are encoded by the functionally redundant Saccharomyces cerevisiae BMH1 and BMH2 genes. We produced and characterized 12 independent bmh1 mutant alleles, whose presence in the cell as the sole 14-3-3 source causes hypersensitivity to genotoxic agents, indicating that Bmh proteins are required for proper response to DNA damage. In particular, the bmh1-103 and bmh1-266 mutant alleles cause defects in G1/S and G2/M DNA damage checkpoints, whereas only the G2/M checkpoint is altered by the bmh1-169 and bmh1-221 alleles. Impaired checkpoint responses correlate with the inability to maintain phosphorylated forms of Rad53 and/or Chk1, suggesting that Bmh proteins might regulate phosphorylation/dephosphorylation of these checkpoint kinases. Moreover, several bmh1 bmh2Δ mutants are defective in resuming DNA replication after transient deoxynucleotide depletion, and all display synthetic effects when also carrying mutations affecting the polα-primase and RPA DNA replication complexes, suggesting a role for Bmh proteins in DNA replication stress response. Finally, the bmh1-169 bmh2Δ and bmh1-170 bmh2Δ mutants show increased rates of spontaneous gross chromosomal rearrangements, indicating that Bmh proteins are required to suppress genome instability.
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Affiliation(s)
- Francisca Lottersberger
- Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, 20126 Milano, Italy
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17
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Aylon Y, Kupiec M. The checkpoint protein Rad24 of Saccharomyces cerevisiae is involved in processing double-strand break ends and in recombination partner choice. Mol Cell Biol 2003; 23:6585-96. [PMID: 12944484 PMCID: PMC193701 DOI: 10.1128/mcb.23.18.6585-6596.2003] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2003] [Revised: 05/08/2003] [Accepted: 06/24/2003] [Indexed: 11/20/2022] Open
Abstract
Upon chromosomal damage, cells activate a checkpoint response that includes cell cycle arrest and a stimulation of DNA repair. The checkpoint protein Rad24 is key to the survival of a single, repairable double-strand break (DSB). However, the low survival of rad24 cells is not due to their inability to arrest cell cycle progression. In rad24 mutants, processing of the broken ends is delayed and protracted, resulting in extended kinetics of DSB repair and in cell death. The limited resection of rad24 mutants also affects recombination partner choice by a mechanism dependent on the length of the interacting homologous donor sequences. Unexpectedly, rad24 cells with a DSB eventually accumulate and die at the G(2)/M phase of the cell cycle. This arrest depends on the spindle checkpoint protein Mad2.
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Affiliation(s)
- Yael Aylon
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv 69978, Israel
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18
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Giannattasio M, Sabbioneda S, Minuzzo M, Plevani P, Muzi-Falconi M. Correlation between checkpoint activation and in vivo assembly of the yeast checkpoint complex Rad17-Mec3-Ddc1. J Biol Chem 2003; 278:22303-8. [PMID: 12672803 DOI: 10.1074/jbc.m301260200] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rad17-Mec3-Ddc1 forms a proliferating cell nuclear antigen-like complex that is required for the DNA damage response in Saccharomyces cerevisiae and acts at an early step of the signal transduction cascade activated by DNA lesions. We used the mec3-dn allele, which causes a dominant negative checkpoint defect in G1 but not in G2, to test the stability of the complex in vivo and to correlate its assembly and disassembly with the mechanisms controlling checkpoint activation. Under physiological conditions, the mutant complex is formed both in G1 and G2, although the mutant phenotype is detectable only in G1, suggesting that is not the presence of the mutant complex per se to cause a checkpoint defect. Our data indicate that the Rad17-Mec3-Ddc1 complex is very stable, and it takes several hours to replace Mec3 with Mec3-dn within a wild type complex. On the other hand, the mutant complex is rapidly assembled when starting from a condition where the complex is not pre-assembled, indicating that the critical factor for the substitution is the disassembly step rather than complex formation. Moreover, the kinetics of mutant complex assembly, starting from conditions in which the wild type form is present, parallels the kinetics of checkpoint inactivation, suggesting that the complex acts in a stoichiometric way, rather than catalytically.
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Affiliation(s)
- Michele Giannattasio
- Dipartimento di Genetica e di Biologia dei Microrganismi, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy
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19
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Durocher D, Smerdon SJ, Yaffe MB, Jackson SP. The FHA domain in DNA repair and checkpoint signaling. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2003; 65:423-31. [PMID: 12760058 DOI: 10.1101/sqb.2000.65.423] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- D Durocher
- Wellcome Trust and Cancer Research Campaign Institute of Cancer and Developmental Biology, Department of Zoology, University of Cambridge, Cambridge CB2 1QR, United Kingdom
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20
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Weinert T, Little E, Shanks L, Admire A, Gardner R, Putnam C, Michelson R, Nyberg K, Sundareshan P. Details and concerns regarding the G2/M DNA damage checkpoint in budding yeast. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2003; 65:433-41. [PMID: 12760059 DOI: 10.1101/sqb.2000.65.433] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- T Weinert
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, USA
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21
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Caspari T, Davies C, Carr AM. Analysis of the fission yeast checkpoint Rad proteins. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2003; 65:451-6. [PMID: 12760061 DOI: 10.1101/sqb.2000.65.451] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- T Caspari
- MRC Cell Mutation Unit, University of Sussex, Falmer, United Kingdom
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22
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Abstract
The faithful replication of the genome is essential for the survival of all organisms. It is not surprising therefore that numerous mechanisms have evolved to ensure that duplication of the genome occurs with only minimal risk of mutation induction. One mechanism of genome destabilization is replication fork demise, which can occur when a translocating fork meets a lesion or adduct in the template. Indeed, the collapse of replication forks has been suggested to occur in every replicative cell cycle making this a potentially significant problem for all proliferating cells. The RecQ helicases, which are essential for the maintenance of genome stability, are thought to function during DNA replication. In particular, RecQ helicase mutants display replication defects and have phenotypes consistent with an inability to efficiently reinitiate replication following replication fork demise. Here, we review some current models for how replication fork repair might be effected, and discuss potential roles for RecQ helicases in this process.
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Affiliation(s)
- Leonard Wu
- Cancer Research UK Laboratories, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
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23
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Giannattasio M, Sommariva E, Vercillo R, Lippi-Boncambi F, Liberi G, Foiani M, Plevani P, Muzi-Falconi M. A dominant-negative MEC3 mutant uncovers new functions for the Rad17 complex and Tel1. Proc Natl Acad Sci U S A 2002; 99:12997-3002. [PMID: 12271137 PMCID: PMC130575 DOI: 10.1073/pnas.202463999] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Rad17-Mec3-Ddc1 complex is essential for the cellular response to genotoxic agents and is thought to be important for sensing DNA lesions. Deletion of any of the RAD17, MEC3 or DDC1 genes abolishes the G(1) and G(2) and impairs the intra-S DNA-damage checkpoints. We characterize a dominant-negative mec3-dn mutation that has an unexpected phenotype. It inactivates the G(1) checkpoint while it leaves the G(2) response functional, thus revealing a difference in the requirements of the DNA-damage response in different phases of the cell cycle. In an attempt to identify the molecular defect imparted by the mutation, we dissected step-by-step the signaling cascade, which is triggered by DNA lesions and requires the activity of Mec1 and Rad53 kinases. The analysis of the phosphorylation state of checkpoint factors and critical protein interactions showed that, in mec3-dn cells, the signal transduction cascade is triggered normally, and the central kinase Mec1 can be activated. In G(1) cells expressing the mutation, the signaling cannot proceed any further along the pathway, indicating that the Rad17 complex acts after the activation of Mec1, possibly recruiting targets for the kinase. We also show that the function of the G(2) checkpoint in mutant cells is maintained by an uncharacterized activity of Tel1, the yeast homologue of ATM. This work thus reports a previously undiscovered role for Tel1 in checkpoint control.
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Affiliation(s)
- Michele Giannattasio
- Dipartimento di Genetica e Biologia dei Microrganismi, Universitá degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy
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24
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Craven RJ, Greenwell PW, Dominska M, Petes TD. Regulation of genome stability by TEL1 and MEC1, yeast homologs of the mammalian ATM and ATR genes. Genetics 2002; 161:493-507. [PMID: 12072449 PMCID: PMC1462148 DOI: 10.1093/genetics/161.2.493] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In eukaryotes, a family of related protein kinases (the ATM family) is involved in regulating cellular responses to DNA damage and telomere length. In the yeast Saccharomyces cerevisiae, two members of this family, TEL1 and MEC1, have functionally redundant roles in both DNA damage repair and telomere length regulation. Strains with mutations in both genes are very sensitive to DNA damaging agents, have very short telomeres, and undergo cellular senescence. We find that strains with the double mutant genotype also have approximately 80-fold increased rates of mitotic recombination and chromosome loss. In addition, the tel1 mec1 strains have high rates of telomeric fusions, resulting in translocations, dicentrics, and circular chromosomes. Similar chromosome rearrangements have been detected in mammalian cells with mutations in ATM (related to TEL1) and ATR (related to MEC1) and in mammalian cells that approach cell crisis.
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Affiliation(s)
- Rolf J Craven
- Department of Biology and Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599-3280, USA
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25
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Oakley TJ, Hickson ID. Defending genome integrity during S-phase: putative roles for RecQ helicases and topoisomerase III. DNA Repair (Amst) 2002; 1:175-207. [PMID: 12509252 DOI: 10.1016/s1568-7864(02)00002-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The maintenance of genome stability is important not only for cell viability, but also for the suppression of neoplastic transformation in higher eukaryotes. It has long been recognised that a common feature of cancer cells is genomic instability. Although the so-called three 'Rs' of genome maintenance, DNA replication, recombination and repair, have historically been studied in isolation, a wealth of recent evidence indicates that these processes are intimately interrelated and interdependent. In this article, we will focus on challenges to the maintenance of genome integrity that arise during the S-phase of the cell cycle, and the possible roles that RecQ helicases and topoisomerase III play in the maintenance of genome integrity during the process of DNA replication.
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Affiliation(s)
- Thomas J Oakley
- Cancer Research UK Laboratories, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
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26
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Cliby WA, Lewis KA, Lilly KK, Kaufmann SH. S phase and G2 arrests induced by topoisomerase I poisons are dependent on ATR kinase function. J Biol Chem 2002; 277:1599-606. [PMID: 11700302 DOI: 10.1074/jbc.m106287200] [Citation(s) in RCA: 156] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ATR, a human phosphatidylinositol 3-kinase-related kinase, is an important component of the cellular response to DNA damage. In the present study, we evaluated the role of ATR in modulating the response of cells to S phase-associated DNA double-stranded breaks induced by topoisomerase poisons. Prolonged exposure to low doses of the topoisomerase I poison topotecan (TPT) resulted in S phase slowing because of diminished DNA synthesis at late-firing replicons. In contrast, brief TPT exposure, as well as prolonged exposure to the topoisomerase II poison etoposide, resulted in subsequent G(2) arrest. These responses were associated with phosphorylation of the checkpoint kinase Chk1. The cell cycle responses and phosphorylation of Chk1 were markedly diminished by forced overexpression of a dominant negative, kinase-inactive allele of ATR. In contrast, deficiency of the related kinase ATM had no effect on these events. The loss of ATR-dependent checkpoint function sensitized GM847 human fibroblasts to the cytotoxic effects of the topoisomerase I poisons TPT and 7-ethyl-10-hydroxycamptothecin, as assessed by inhibition of colony formation, increased trypan blue uptake, and development of apoptotic morphological changes. Expression of kdATR also sensitized GM847 cells to the cytotoxic effects of prolonged low dose etoposide and doxorubicin, albeit to a smaller extent. Collectively, these results not only suggest that ATR is important in responding to the replication-associated DNA damage from topoisomerase poisons, but also support the view that ATM and ATR have unique roles in activating the downstream kinases that participate in cell cycle checkpoints.
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Affiliation(s)
- William A Cliby
- Department of Obstetrics and Gynecology, Mayo Clinic, Rochester, Minnesota 55905, USA.
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27
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Abstract
Checkpoint kinase 2 (Chk2) is emerging as a key mediator of diverse cellular responses to genotoxic stress, guarding the integrity of the genome throughout eukaryotic evolution. Recent studies show the fundamental role of Chk2 in the network of genome-surveillance pathways that coordinate cell-cycle progression with DNA repair and cell survival or death. Defects in Chk2 contribute to the development of both hereditary and sporadic human cancers, and earmark this kinase as a candidate tumour suppressor and an attractive target for drug discovery.
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Affiliation(s)
- J Bartek
- Danish Cancer Society, Institute of Cancer Biology, Strandboulevarden 49, DK-2100 Copenhagen Ø, Denmark.
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28
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Wang SW, Goodwin A, Hickson ID, Norbury CJ. Involvement of Schizosaccharomyces pombe Srs2 in cellular responses to DNA damage. Nucleic Acids Res 2001; 29:2963-72. [PMID: 11452021 PMCID: PMC55813 DOI: 10.1093/nar/29.14.2963] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
In the budding yeast Saccharomyces cerevisiae the Srs2/RadH DNA helicase promotes survival after ultraviolet (UV) irradiation, and has been implicated in DNA repair, recombination and checkpoint signalling following DNA damage. A second helicase, Sgs1, is the S.cerevisiae homologue of the human BLM and WRN proteins, which are defective in cancer predisposition and/or premature ageing syndromes. Saccharomyces cerevisiae cells lacking both Srs2 and Sgs1 exhibit a severe growth defect. We have identified an Srs2 orthologue in the fission yeast Schizosaccharomyces pombe, and have investigated its role in responses to UV irradiation and inhibition of DNA replication. Deletion of fission yeast srs2 caused spontaneous hyper-recombination and UV sensitivity, and simultaneous deletion of the SGS1 homologue rqh1 caused a severe growth defect reminiscent of that seen in the equivalent S.cerevisiae mutant. However, unlike in budding yeast, inactivation of the homologous recombination pathway did not suppress this growth defect. Indeed, the homologous recombination pathway was required for maintenance of normal fission yeast viability in the absence of Srs2, and loss of homologous recombination and loss of Srs2 contributed additively to UV sensitivity. We conclude that Srs2 plays related, but not identical, roles in the two yeast species.
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Affiliation(s)
- S W Wang
- Imperial Cancer Research Fund Molecular Oncology Laboratory, University of Oxford Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Oxford OX3 9DS, UK
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29
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Abstract
We find budding yeast Rad9 in two distinct, large, and soluble complexes in cell extracts. The larger (> or =850 kDa) complex, found in nondamaged cells, contains hypophosphorylated Rad9, whereas the smaller (560 kDa) complex, which forms after DNA damage, contains hyperphosphorylated Rad9 and Rad53. This smaller Rad9 complex is capable of catalyzing phosphorylation and release of active Rad53 kinase, a process requiring the kinase activity of Rad53. However, Mec1 and Tel1 are no longer required once the 560 kDa complex has been formed. We propose a model whereby Mec1/Tel1-dependent hyperphosphorylation of Rad9 results in formation of the smaller Rad9 complex and recruitment of Rad53. This complex then catalyzes activation of Rad53 by acting as a scaffold that brings Rad53 molecules into close proximity, facilitating Rad53 in trans autophosphorylation and subsequent release of activated Rad53.
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Affiliation(s)
- C S Gilbert
- Imperial Cancer Research Fund, Clare Hall Laboratories, CDC Laboratory, South Mimms, EN6 3LD, Hertfordshire, United Kingdom
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30
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Paciotti V, Clerici M, Scotti M, Lucchini G, Longhese MP. Characterization of mec1 kinase-deficient mutants and of new hypomorphic mec1 alleles impairing subsets of the DNA damage response pathway. Mol Cell Biol 2001; 21:3913-25. [PMID: 11359899 PMCID: PMC87054 DOI: 10.1128/mcb.21.12.3913-3925.2001] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
DNA damage checkpoints lead to the inhibition of cell cycle progression following DNA damage. The Saccharomyces cerevisiae Mec1 checkpoint protein, a phosphatidylinositol kinase-related protein, is required for transient cell cycle arrest in response to DNA damage or DNA replication defects. We show that mec1 kinase-deficient (mec1kd) mutants are indistinguishable from mec1Delta cells, indicating that the Mec1 conserved kinase domain is required for all known Mec1 functions, including cell viability and proper DNA damage response. Mec1kd variants maintain the ability to physically interact with both Ddc2 and wild-type Mec1 and cause dominant checkpoint defects when overproduced in MEC1 cells, impairing the ability of cells to slow down S phase entry and progression after DNA damage in G(1) or during S phase. Conversely, an excess of Mec1kd in MEC1 cells does not abrogate the G(2)/M checkpoint, suggesting that Mec1 functions required for response to aberrant DNA structures during specific cell cycle stages can be separable. In agreement with this hypothesis, we describe two new hypomorphic mec1 mutants that are completely defective in the G(1)/S and intra-S DNA damage checkpoints but properly delay nuclear division after UV irradiation in G(2). The finding that these mutants, although indistinguishable from mec1Delta cells with respect to the ability to replicate a damaged DNA template, do not lose viability after UV light and methyl methanesulfonate treatment suggests that checkpoint impairments do not necessarily result in hypersensitivity to DNA-damaging agents.
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Affiliation(s)
- V Paciotti
- Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano-Bicocca, 20126 Milan, Italy
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31
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Abstract
The initiation of DNA replication in eukaryotic cells is tightly controlled to ensure that the genome is faithfully duplicated once each cell cycle. Genetic and biochemical studies in several model systems indicate that initiation is mediated by a common set of proteins, present in all eukaryotic species, and that the activities of these proteins are regulated during the cell cycle by specific protein kinases. Here we review the properties of the initiation proteins, their interactions with each other, and with origins of DNA replication. We also describe recent advances in understanding how the regulatory protein kinases control the progress of the initiation reaction. Finally, we describe the checkpoint mechanisms that function to preserve the integrity of the genome when the normal course of genome duplication is perturbed by factors that damage the DNA or inhibit DNA synthesis.
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Affiliation(s)
- T J Kelly
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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32
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Wakayama T, Kondo T, Ando S, Matsumoto K, Sugimoto K. Pie1, a protein interacting with Mec1, controls cell growth and checkpoint responses in Saccharomyces cerevisiae. Mol Cell Biol 2001; 21:755-64. [PMID: 11154263 PMCID: PMC86667 DOI: 10.1128/mcb.21.3.755-764.2001] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In eukaryotes, the ATM and ATR family proteins play a critical role in the DNA damage and replication checkpoint controls. These proteins are characterized by a kinase domain related to the phosphatidylinositol 3-kinase, but they have the ability to phosphorylate proteins. In budding yeast, the ATR family protein Mec1/Esr1 is essential for checkpoint responses and cell growth. We have isolated the PIE1 gene in a two-hybrid screen for proteins that interact with Mec1, and we show that Pie1 interacts physically with Mec1 in vivo. Like MEC1, PIE1 is essential for cell growth, and deletion of the PIE1 gene causes defects in the DNA damage and replication block checkpoints similar to those observed in mec1Delta mutants. Rad53 hyperphosphorylation following DNA damage and replication block is also decreased in pie1Delta cells, as in mec1Delta cells. Pie1 has a limited homology to fission yeast Rad26, which forms a complex with the ATR family protein Rad3. Mutation of the region in Pie1 homologous to Rad26 results in a phenotype similar to that of the pie1Delta mutation. Mec1 protein kinase activity appears to be essential for checkpoint responses and cell growth. However, Mec1 kinase activity is unaffected by the pie1Delta mutation, suggesting that Pie1 regulates some essential function other than Mec1 kinase activity. Thus, Pie1 is structurally and functionally related to Rad26 and interacts with Mec1 to control checkpoints and cell proliferation.
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Affiliation(s)
- T Wakayama
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-0814, Japan
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33
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Abstract
As recently as six years ago, three human diseases with similar phenotypes were mistakenly believed to be caused by a single genetic defect. The three diseases, Ataxia-telangiectasia, Nijmegen breakage syndrome, and an AT-like disorder are now known, however, to have defects in three separate genes: ATM, NBS1, and MRE11. Furthermore, new recent studies have shown now that all three gene products interact; the ATM kinase phosphorylates NBS1, which, in turn, associates with MRE11 to regulate DNA repair. Remarkably or expectedly, depending on one's point of view, the similarity in disease phenotypes is evidently due to defects in a common DNA repair pathway.
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Affiliation(s)
- R J Michelson
- Department of Molecular and Cellular Biology, University of Arizona, Tucson 85721-0106, USA
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34
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Snaith HA, Brown GW, Forsburg SL. Schizosaccharomyces pombe Hsk1p is a potential cds1p target required for genome integrity. Mol Cell Biol 2000; 20:7922-32. [PMID: 11027263 PMCID: PMC86403 DOI: 10.1128/mcb.20.21.7922-7932.2000] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The fission yeast Hsk1p kinase is an essential activator of DNA replication. Here we report the isolation and characterization of a novel mutant allele of the gene. Consistent with its role in the initiation of DNA synthesis, hsk1(ts) genetically interacts with several S-phase mutants. At the restrictive temperature, hsk1(ts) cells suffer abnormal S phase and loss of nuclear integrity and are sensitive to both DNA-damaging agents and replication arrest. Interestingly, hsk1(ts) mutants released to the restrictive temperature after early S-phase arrest in hydroxyurea (HU) are able to complete bulk DNA synthesis but they nevertheless undergo an abnormal mitosis. These findings indicate a second role for hsk1 subsequent to HU arrest. Consistent with a later S-phase role, hsk1(ts) is synthetically lethal with Deltarqh1 (RecQ helicase) or rad21ts (cohesin) mutants and suppressed by Deltacds1 (RAD53 kinase) mutants. We demonstrate that Hsk1p undergoes Cds1p-dependent phosphorylation in response to HU and that it is a direct substrate of purified Cds1p kinase in vitro. These results indicate that the Hsk1p kinase is a potential target of Cds1p regulation and that its activity is required after replication initiation for normal mitosis.
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Affiliation(s)
- H A Snaith
- Molecular Biology and Virology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037-1099, USA
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35
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Kim M, Lee W, Park J, Kim JB, Jang YK, Seong RH, Choe SY, Park SD. The stress-activated MAP kinase Sty1/Spc1 and a 3'-regulatory element mediate UV-induced expression of the uvi15(+) gene at the post-transcriptional level. Nucleic Acids Res 2000; 28:3392-402. [PMID: 10954610 PMCID: PMC110690 DOI: 10.1093/nar/28.17.3392] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Exposure of Schizosaccharomyces pombe cells to UV light results in increased uvi15(+) gene expression at both the mRNA and protein levels, leading to elevated cell survival. This UV-induced expression of the uvi15(+) gene was reduced in Deltasty1 and Deltawis1 cells lacking the stress-activated protein kinase pathway, but not in DNA damage checkpoint mutants. To further understand the cellular mechanisms responsible for this UV-induced expression, the transcription rate and mRNA half-life were investigated. Transcription run-on assays revealed that the rate of uvi15(+) transcription was increased 1.8-fold regardless of Sty1 when cells were UV irradiated. The half-life of uvi15(+) mRNA was also increased 1.5-fold after UV irradiation, but it was decreased in the Deltasty1 background for both basal and UV-induced mRNAs, indicating that the stress-activated MAPK cascade can mediate UV-induced gene expression by increasing mRNA half-life. Deletion analyses identified a 54 nt element downstream of the distal poly(A) site, which was involved in the increased half-life of uvi15(+) mRNA. These results suggest that both Sty1 and the 3'-regulatory element regulate UV-induced expression of the uvi15(+) gene at the post-transcriptional level.
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Affiliation(s)
- M Kim
- School of Biological Sciences, College of Natural Sciences, Seoul National University, Seoul 151-742, Republic of Korea
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36
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Paciotti V, Clerici M, Lucchini G, Longhese MP. The checkpoint protein Ddc2, functionally related to S. pombe Rad26, interacts with Mec1 and is regulated by Mec1-dependent phosphorylation in budding yeast. Genes Dev 2000. [DOI: 10.1101/gad.14.16.2046] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
DDC2 is a novel component of the DNA integrity checkpoint pathway, which is required for proper checkpoint response to DNA damage and to incomplete DNA replication. Moreover, Ddc2 overproduction causes sensitivity to DNA-damaging agents and checkpoint defects. Ddc2 physically interacts with Mec1 and undergoes Mec1-dependent phosphorylation both in vitro and in vivo. The phosphorylation of Ddc2 takes place in late S phase and in G2 phase during an unperturbed cell cycle and is further increased in response to DNA damage. Because Ddc2 phosphorylation does not require any other known tested checkpoint factors but Mec1, the Ddc2–Mec1 complex might respond to the presence of some DNA structures independently of the other known checkpoint proteins. Our findings suggest that Ddc2 may be the functional homolog of Schizosaccharomyces pombe Rad26, strengthening the hypothesis that the mechanisms leading to checkpoint activation are conserved throughout evolution.
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37
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Abstract
DNA damage causes cell-cycle delay before S phase, during replication and before mitosis. This involves a number of highly conserved proteins that sense DNA damage and signal the cell-cycle machinery. Kinases that were initially discovered in yeast model systems have recently been shown to regulate the regulators of cyclin-dependent kinases and to control the stability of p53. This shows the importance of checkpoint proteins for maintaining genome stability. Here, we discuss recent data from yeast and metazoans that suggest a remarkable conservation of the organization of the G2 DNA-damage checkpoint pathway.
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Affiliation(s)
- M J O'Connell
- Trescowthick Research Laboratories, Peter MacCallum Cancer Institute, Locked Bag 1, A'Beckett Street, Melbourne, Victoria 8006, Australia
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38
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Forsburg SL, Hodson JA. Mitotic replication initiation proteins are not required for pre-meiotic S phase. Nat Genet 2000; 25:263-8. [PMID: 10888871 DOI: 10.1038/77015] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Initiation of mitotic DNA replication in eukaryotes requires conserved factors, including Cdc18/CDC6 and minichromosome maintenance (MCM) proteins. We show here that these proteins are not essential for meiotic DNA replication or subsequent meiotic divisions in fission yeast. In addition, vegetative replication checkpoint genes are not required for the arrest of meiotic divisions in response to pre-meiotic S-phase delays. Genes essential for other aspects of vegetative DNA replication, however, including polymerases and DNA ligase, are also required for pre-meiotic DNA synthesis. Our results indicate that the process of replication initiation and checkpoint control may be fundamentally different in mitotic and meiotic cells.
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Affiliation(s)
- S L Forsburg
- Molecular Biology and Virology Laboratory, The Salk Institute for Biological Studies, La Jolla, California, USA.
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Affiliation(s)
- R Bosotti
- Dept of Biology, Pharmacia & Upjohn, Viale Pasteur 10, 20014, Nerviano (MI), Italy
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40
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de Klein A, Muijtjens M, van Os R, Verhoeven Y, Smit B, Carr AM, Lehmann AR, Hoeijmakers JH. Targeted disruption of the cell-cycle checkpoint gene ATR leads to early embryonic lethality in mice. Curr Biol 2000; 10:479-82. [PMID: 10801416 DOI: 10.1016/s0960-9822(00)00447-4] [Citation(s) in RCA: 330] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Checkpoints of DNA integrity are conserved throughout evolution, as are the kinases ATM (Ataxia Telangiectasia mutated) and ATR (Ataxia- and Rad-related), which are related to phosphatidylinositol (PI) 3-kinase [1] [2] [3]. The ATM gene is not essential, but mutations lead to ataxia telangiectasia (AT), a pleiotropic disorder characterised by radiation sensitivity and cellular checkpoint defects in response to ionising radiation [4] [5] [6]. The ATR gene has not been associated with human syndromes and, structurally, is more closely related to the canonical yeast checkpoint genes rad3(Sp) and MEC1(Sc) [7] [8]. ATR has been implicated in the response to ultraviolet (UV) radiation and blocks to DNA synthesis [8] [9] [10] [11], and may phosphorylate p53 [12] [13], suggesting that ATM and ATR may have similar and, perhaps, complementary roles in cell-cycle control after DNA damage. Here, we report that targeted inactivation of ATR in mice by disruption of the kinase domain leads to early embryonic lethality before embryonic day 8.5 (E8.5). Heterozygous mice were fertile and had no aberrant phenotype, despite a lower ATR mRNA level. No increase was observed in the sensitivity of ATR(+/-) embryonic stem (ES) cells to a variety of DNA-damaging agents. Attempts to target the remaining wild-type ATR allele in heterozygous ATR(+/-) ES cells failed, supporting the idea that loss of both alleles of the ATR gene, even at the ES-cell level, is lethal. Thus, in contrast to the closely related checkpoint gene ATM, ATR has an essential function in early mammalian development.
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Affiliation(s)
- A de Klein
- MGC Department of Cell Biology and Genetics, Center for Biomedical Genetics, Erasmus University, Rotterdam, The Netherlands.
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41
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Caspari T, Dahlen M, Kanter-Smoler G, Lindsay HD, Hofmann K, Papadimitriou K, Sunnerhagen P, Carr AM. Characterization of Schizosaccharomyces pombe Hus1: a PCNA-related protein that associates with Rad1 and Rad9. Mol Cell Biol 2000; 20:1254-62. [PMID: 10648611 PMCID: PMC85258 DOI: 10.1128/mcb.20.4.1254-1262.2000] [Citation(s) in RCA: 198] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Hus1 is one of six checkpoint Rad proteins required for all Schizosaccharomyces pombe DNA integrity checkpoints. MYC-tagged Hus1 reveals four discrete forms. The main form, Hus1-B, participates in a protein complex with Rad9 and Rad1, consistent with reports that Rad1-Hus1 immunoprecipitation is dependent on the rad9(+) locus. A small proportion of Hus1-B is intrinsically phosphorylated in undamaged cells and more becomes phosphorylated after irradiation. Hus1-B phosphorylation is not increased in cells blocked in early S phase with hydroxyurea unless exposure is prolonged. The Rad1-Rad9-Hus1-B complex is readily detectable, but upon cofractionation of soluble extracts, the majority of each protein is not present in this complex. Indirect immunofluorescence demonstrates that Hus1 is nuclear and that this localization depends on Rad17. We show that Rad17 defines a distinct protein complex in soluble extracts that is separate from Rad1, Rad9, and Hus1. However, two-hybrid interaction, in vitro association and in vivo overexpression experiments suggest a transient interaction between Rad1 and Rad17.
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Affiliation(s)
- T Caspari
- MRC Cell Mutation Unit, University of Sussex, Brighton BN1 9RR, United Kingdom
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42
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Abstract
The many events of meiotic prophase can now be viewed as a series of specialized incidents that are monitored by meiotic checkpoints, some of which are similar to their mitotic counterparts, and some of which are probably unique to meiosis. This shift in perspective means that meiotic sterility in mammals must be reexamined and viewed as the result of errors subject to meiotic checkpoint controls. Like their mitotic counterparts, the meiotic checkpoints detect defects and halt normal progression until these mistakes can be repaired. Some of these checkpoints utilize mitotic checkpoint proteins, others may involve meiotic-specific proteins, or splice forms. If repair is impossible, the checkpoints then either trigger immediate apoptosis or cause an arrest of meiotic progression followed by eventual cell death. If a sufficient number of spermatocytes are involved, either alternative results in sterility. Identification of these meiotic checkpoints and delineation of the signal transduction cascades involved has only just begun. While yeast, or other model organisms, may provide clues to some of these pathways, others appears to have arisen during vertebrate evolution. The study of mammalian meiosis has entered a new era and the foundations are being laid for a growing understanding of the many problems that may contribute to sterility.
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Affiliation(s)
- T Ashley
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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43
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Kim ST, Lim DS, Canman CE, Kastan MB. Substrate specificities and identification of putative substrates of ATM kinase family members. J Biol Chem 1999; 274:37538-43. [PMID: 10608806 DOI: 10.1074/jbc.274.53.37538] [Citation(s) in RCA: 573] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Ataxia telangiectasia mutated (ATM) phosphorylates p53 protein in response to ionizing radiation, but the complex phenotype of AT cells suggests that it must have other cellular substrates as well. To identify substrates for ATM and the related kinases ATR and DNA-PK, we optimized in vitro kinase assays and developed a rapid peptide screening method to determine general phosphorylation consensus sequences. ATM and ATR require Mn(2+), but not DNA ends or Ku proteins, for optimal in vitro activity while DNA-PKCs requires Mg(2+), DNA ends, and Ku proteins. From p53 peptide mutagenesis analysis, we found that the sequence S/TQ is a minimal essential requirement for all three kinases. In addition, hydrophobic amino acids and negatively charged amino acids immediately NH(2)-terminal to serine or threonine are positive determinants and positively charged amino acids in the region are negative determinants for substrate phosphorylation. We determined a general phosphorylation consensus sequence for ATM and identified putative in vitro targets by using glutathione S-transferase peptides as substrates. Putative ATM in vitro targets include p95/nibrin, Mre11, Brca1, Rad17, PTS, WRN, and ATM (S440) itself. Brca2, phosphatidylinositol 3-kinase, and DNA-5B peptides were phosphorylated specifically by ATR, and DNA Ligase IV is a specific in vitro substrate of DNA-PK.
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Affiliation(s)
- S T Kim
- Department of Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
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Shimada M, Okuzaki D, Tanaka S, Tougan T, Tamai KK, Shimoda C, Nojima H. Replication factor C3 of Schizosaccharomyces pombe, a small subunit of replication factor C complex, plays a role in both replication and damage checkpoints. Mol Biol Cell 1999; 10:3991-4003. [PMID: 10588638 PMCID: PMC25738 DOI: 10.1091/mbc.10.12.3991] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We report here the isolation and functional analysis of the rfc3(+) gene of Schizosaccharomyces pombe, which encodes the third subunit of replication factor C (RFC3). Because the rfc3(+) gene was essential for growth, we isolated temperature-sensitive mutants. One of the mutants, rfc3-1, showed aberrant mitosis with fragmented or unevenly separated chromosomes at the restrictive temperature. In this mutant protein, arginine 216 was replaced by tryptophan. Pulsed-field gel electrophoresis suggested that rfc3-1 cells had defects in DNA replication. rfc3-1 cells were sensitive to hydroxyurea, methanesulfonate (MMS), and gamma and UV irradiation even at the permissive temperature, and the viabilities after these treatments were decreased. Using cells synchronized in early G2 by centrifugal elutriation, we found that the replication checkpoint triggered by hydroxyurea and the DNA damage checkpoint caused by MMS and gamma irradiation were impaired in rfc3-1 cells. Association of Rfc3 and Rad17 in vivo and a significant reduction of the phosphorylated form of Chk1 in rfc3-1 cells after treatments with MMS and gamma or UV irradiation suggested that the checkpoint signal emitted by Rfc3 is linked to the downstream checkpoint machinery via Rad17 and Chk1. From these results, we conclude that rfc3(+) is required not only for DNA replication but also for replication and damage checkpoint controls, probably functioning as a checkpoint sensor.
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Affiliation(s)
- M Shimada
- Department of Molecular Genetics, Research Institute for Microbial Diseases, Osaka University, Osaka 565-0871, Japan
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45
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Edwards RJ, Bentley NJ, Carr AM. A Rad3-Rad26 complex responds to DNA damage independently of other checkpoint proteins. Nat Cell Biol 1999; 1:393-8. [PMID: 10559981 DOI: 10.1038/15623] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The conserved PIK-related kinase Rad3 is required for all DNA-integrity-checkpoint responses in fission yeast. Here we report a stable association between Rad3 and Rad26 in soluble protein extracts. Rad26 shows Rad3-dependent phosphorylation after DNA damage. Unlike phosphorylation of Hus1, Crb2/Rhp9, Cds1 and Chk1, phosphorylation of Rad26 does not require other known checkpoint proteins. Rad26 phosphorylation is the first biochemical marker of Rad3 function, indicating that Rad3-related checkpoint kinases may have a direct role in DNA-damage recognition.
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Affiliation(s)
- R J Edwards
- MRC Cell Mutation Unit, Sussex University, Falmer BN1 9RR, UK
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46
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47
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Gardner R, Putnam CW, Weinert T. RAD53, DUN1 and PDS1 define two parallel G2/M checkpoint pathways in budding yeast. EMBO J 1999; 18:3173-85. [PMID: 10357828 PMCID: PMC1171398 DOI: 10.1093/emboj/18.11.3173] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Eukaryotic checkpoint genes regulate multiple cellular responses to DNA damage. In this report, we examine the roles of budding yeast genes involved in G2/M arrest and tolerance to UV exposure. A current model posits three gene classes: those encoding proteins acting on damaged DNA (e.g. RAD9 and RAD24), those transducing a signal (MEC1, RAD53 and DUN1) or those participating more directly in arrest (PDS1). Here, we define important features of the pathways subserved by those genes. MEC1, which we find is required for both establishment and maintenance of G2/M arrest, mediates this arrest through two parallel pathways. One pathway requires RAD53 and DUN1 (the 'RAD53 pathway'); the other pathway requires PDS1. Each pathway independently contributes approximately 50% to G2/M arrest, effects demonstrable after cdc13-induced damage or a double-stranded break inflicted by the HO endonuclease. Similarly, both pathways contribute independently to tolerance of UV irradiation. How the parallel pathways might interact ultimately to achieve arrest is not yet understood, but we do provide evidence that neither the RAD53 nor the PDS1 pathway appears to maintain arrest by inhibiting adaptation. Instead, we think it likely that both pathways contribute to establishing and maintaining arrest.
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Affiliation(s)
- R Gardner
- Department of Molecular and Cellular Biology, The University of Arizona, PO Box 21016, Tucson, AZ 85721-0106, USA
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48
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Craig R, Norbury C. The novel murine calmodulin-binding protein Sha1 disrupts mitotic spindle and replication checkpoint functions in fission yeast. J Cell Sci 1998; 111 ( Pt 24):3609-19. [PMID: 9819352 DOI: 10.1242/jcs.111.24.3609] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Entry into mitosis is normally blocked in eukaryotic cells that have not completed replicative DNA synthesis; this ‘S-M’ checkpoint control is fundamental to the maintenance of genomic integrity. Mutants of the fission yeast Schizosaccharomyces pombe defective in the S-M checkpoint fail to arrest the cell cycle when DNA replication is inhibited and hence attempt mitosis and cell division with unreplicated chromosomes, resulting in the ‘cut’ phenotype. In an attempt to identify conserved molecules involved in the S-M checkpoint we have screened a regulatable murine cDNA library in S. pombe and have identified cDNAs that induce the cut phenotype in cells arrested in S phase by hydroxyurea. One such cDNA encodes a novel protein with multiple calmodulin-binding motifs that, in addition to its effects on the S-M checkpoint, perturbed mitotic spindle functions, although spindle pole duplication was apparently normal. Both aspects of the phenotype induced by this cDNA product, which we term Sha1 (for spindle and hydroxyurea checkpoint abnormal), were suppressed by simultaneous overexpression of calmodulin. Sha1 is structurally related to the product of the Drosophila gene abnormal spindle (asp). These data suggest that calmodulin-binding protein(s) are important in the co-ordination of mitotic spindle functions with mitotic entry in fission yeast, and probably also in multicellular eukaryotes.
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Affiliation(s)
- R Craig
- Imperial Cancer Research Fund, Molecular Oncology Laboratory, University of Oxford Institute of Molecular Medicine, John Radcliffe Hospital, Oxford OX3 9DS, UK
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49
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Dean FB, Lian L, O'Donnell M. cDNA cloning and gene mapping of human homologs for Schizosaccharomyces pombe rad17, rad1, and hus1 and cloning of homologs from mouse, Caenorhabditis elegans, and Drosophila melanogaster. Genomics 1998; 54:424-36. [PMID: 9878245 DOI: 10.1006/geno.1998.5587] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Mutations in DNA repair/cell cycle checkpoint genes can lead to the development of cancer. The cloning of human homologs of yeast DNA repair/cell cycle checkpoint genes should yield candidates for human tumor suppressor genes as well as identifying potential targets for cancer therapy. The Schizosaccharomyces pombe genes rad17, rad1, and hus1 have been identified as playing roles in DNA repair and cell cycle checkpoint control pathways. We have cloned the cDNA for the human homolog of S. pombe rad17, RAD17, which localizes to chromosomal location 5q13 by fluorescence in situ hybridization and radiation hybrid mapping; the cDNA for the human homolog of S. pombe rad1, RAD1, which maps to 5p14-p13.2; and the cDNA for the human homolog of S. pombe hus1, HUS1, which maps to 7p13-p12. The human gene loci have previously been identified as regions containing tumor suppressor genes. In addition, we report the cloning of the cDNAs for genes related to S. pombe rad17, rad9, rad1, and hus1 from mouse, Caenorhabditis elegans, and Drosophila melanogaster. These include Rad17 and Rad9 from D. melanogaster, hpr-17 and hpr-1 from C. elegans, and RAD1 and HUS1 from mouse. The identification of homologs of the S. pombe rad checkpoint genes from mammals, arthropods, and nematodes indicates that this cell cycle checkpoint pathway is conserved throughout eukaryotes.
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Affiliation(s)
- F B Dean
- The Rockefeller University, The Howard Hughes Medical Institute, 1230 York Avenue, New York, New York, 10021, USA.
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50
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Mendenhall MD, Hodge AE. Regulation of Cdc28 cyclin-dependent protein kinase activity during the cell cycle of the yeast Saccharomyces cerevisiae. Microbiol Mol Biol Rev 1998; 62:1191-243. [PMID: 9841670 PMCID: PMC98944 DOI: 10.1128/mmbr.62.4.1191-1243.1998] [Citation(s) in RCA: 300] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cyclin-dependent protein kinase (CDK) encoded by CDC28 is the master regulator of cell division in the budding yeast Saccharomyces cerevisiae. By mechanisms that, for the most part, remain to be delineated, Cdc28 activity controls the timing of mitotic commitment, bud initiation, DNA replication, spindle formation, and chromosome separation. Environmental stimuli and progress through the cell cycle are monitored through checkpoint mechanisms that influence Cdc28 activity at key cell cycle stages. A vast body of information concerning how Cdc28 activity is timed and coordinated with various mitotic events has accrued. This article reviews that literature. Following an introduction to the properties of CDKs common to many eukaryotic species, the key influences on Cdc28 activity-cyclin-CKI binding and phosphorylation-dephosphorylation events-are examined. The processes controlling the abundance and activity of key Cdc28 regulators, especially transcriptional and proteolytic mechanisms, are then discussed in detail. Finally, the mechanisms by which environmental stimuli influence Cdc28 activity are summarized.
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Affiliation(s)
- M D Mendenhall
- L. P. Markey Cancer Center, University of Kentucky, Lexington, Kentucky 40536-0096, USA.
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