Inactivation of Cdc13p TriggersMEC1-dependent Apoptotic Signals in Yeast

Department of Pharmacology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 05/2003; 278(17):15136-41. DOI: 10.1074/jbc.M212808200
Source: PubMed


Inactivation of the budding yeast telomere binding protein Cdc13 results in abnormal telomeres (exposed long G-strands) and
activation of the DNA damage checkpoint. In the current study, we show that inactivation of Cdc13p induces apoptotic signals
in yeast, as evidenced by caspase activation, increased reactive oxygen species production, and flipping of phosphatidylserine
in the cytoplasmic membrane. These apoptotic signals were suppressed in a mitochondrial (ρo) mutant. Moreover, mitochondrial proteins (e.g. MTCO3) were identified as multicopy suppressors of cdc13-1, suggesting the involvement of mitochondrial functions in telomere-initiated apoptotic signaling. These telomere-initiated
apoptotic signals were also shown to depend onMEC1, but not TEL1, and were antagonized byMRE11. Our results are consistent with a model in which single-stranded G-tails in the cdc13-1 mutant triggerMEC1-dependent apoptotic signaling in yeast.

    • "Importantly, our results suggest that the arv1Δ mutant activates an Exo1-and MRX (Mre11–Rad50–Xrs1)-dependent DNA damage checkpoint, and that overexpression of telomerase subunits counteracts apoptotic signals triggered by impaired sphingolipid metabolism. As dysfunctional telomeres have been shown to result in activation of the DNA damage checkpoint (Dewar and Lydall, 2010; Longhese, 2008; Maringele and Lydall, 2002; Teo and Jackson, 2001; Zubko et al., 2004), cell cycle arrest in G2/M (IJpma and Greider, 2003; Pang et al., 2003; Qi et al., 2008) and apoptotic cell death (Qi et al., 2008, 2003), it is tempting to speculate that the telomeric regions in the arv1Δ mutant are not protected from DNA damage checkpoint signaling. Previous observations have shown that a reduction in the amount of complex sphingolipids caused by AbA treatment or acc1 mutation, but not lcb1-100 mutation, induced cell cycle G2/M arrest (Al-Feel et al., 2003; Endo et al., 1997; Jenkins and Hannun, 2001) and that the arv1Δ mutant exhibited a synthetic growth defect with the cdc13-1 mutant leading to uncapped telomeres (Addinall et al., 2008) are consistent with the hypothesis. "
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    ABSTRACT: In eukaryotic organisms including mammals, nematodes, and yeasts, the ends of chromosomes, telomeres are clustered at the nuclear periphery. Telomere clustering is assumed to be functionally important because proper organization of chromosomes is necessary for proper genome function and stability. However, the mechanisms and physiological roles of telomere clustering remain poorly understood. In this study, we demonstrate a role for sphingolipids in telomere clustering in the budding yeast Saccharomyces cerevisiae. Because abnormal sphingolipid metabolism causes down-regulation of expression levels of genes involved in telomere organization, sphingolipids appear to control telomere clustering at the transcriptional level. Additionally, the data presented here provide evidence that telomere clustering is required to protect chromosome ends from DNA-damage checkpoint signaling. As sphingolipids are found in all eukaryotes, we speculate that sphingolipid-based regulation of telomere clustering and the protective role of telomere clusters in maintaining genome stability might be conserved in eukaryotes. © 2015. Published by The Company of Biologists Ltd.
    No preview · Article · Jun 2015 · Journal of Cell Science
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    • "GUP1 is involved in a wide range of cellular processes, some of which are associated directly or indirectly with apoptosis, such as rafts integrity and lipids metabolism [17,18,21,30,31,34], cytoskeleton polarization [35,37], and telomere length [36,38]. In the present work, we assess apoptotic markers for gup1∆ mutant strain and compare them with Wt, under two different conditions documented to induce apoptosis in yeast: chronological aging and acetic acid [8,39]. "
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    ABSTRACT: During the past years, yeast has been successfully established as a model to study mechanisms of programmed cell death regulation. Saccharomyces cerevisiae commits to cell death showing typical hallmarks of metazoan apoptosis, in response to different stimuli. Gup1p, an O-acyltransferase, is required for several cellular processes that are related to apoptosis development, such as rafts integrity and stability, lipid metabolism including GPI anchor correct remodeling, proper mitochondrial and vacuole function, bud site selection and actin dynamics. Therefore, we hypothesize that apoptotic process would be affected by GUP1 deletion. In the present work we used two known apoptosis inducing conditions, chronological aging and acetic acid, to assess several apoptotic markers in gup1∆ mutant strain. We found that this mutant presents a significantly reduced chronological lifespan as compared to Wt and it is also highly sensitive to acetic acid treatment. In addition, it presents extremely high levels of ROS. There were notorious differences on apoptotic markers between Wt and gup1∆ mutant strains, namely on the maintenance of plasma membrane integrity, on the phosphatidylserine externalization, on the depolarization of mitochondrial membrane and on the chromatin condensation. Those suggested that the mutant, under either condition, probably dies of necrosis and not from apoptosis. To Gup1p has been assigned an important function on lipid rafts assembly/integrity, lipid metabolism and GPI anchor remodeling. Our results provide, for the first time, the connection of the integrity of yeast lipid rafts and apoptosis induction and/or signaling, giving new insights into the molecular mechanisms underlying this process in yeast.
    Full-text · Article · May 2012 · BMC Microbiology
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    • "Release of cyt c was also shown in cells treated with amiodarone [13], H 2 O 2 [12] and in asf1/cia1Δ [14] or Cdc48 S565G mutants [15]. Complexes III and IV were found to be involved in death induced by amiodarone [13] or abnormal telomeres (cdc13Δ) [16], respectively, while deletion of different genes encoding proteins from the electron transport chain rendered cells more sensitive to apoptosis induced by overexpression of yeast Aifhomologous mitochondrion-associated inducer of death (AMID) orthologue, NDI1 [17]. Formation of petites was shown to accompany apoptotic cell death induced by glucose (2%, w/v) in the absence of additional nutrients [18]. "
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    ABSTRACT: Mitochondrial involvement in yeast apoptosis is probably the most unifying feature in the field. Reports proposing a role for mitochondria in yeast apoptosis present evidence ranging from the simple observation of ROS accumulation in the cell to the identification of mitochondrial proteins mediating cell death. Although yeast is unarguably a simple model it reveals an elaborate regulation of the death process involving distinct proteins and most likely different pathways, depending on the insult, growth conditions and cell metabolism. This complexity may be due to the interplay between the death pathways and the major signalling routes in the cell, contributing to a whole integrated response. The elucidation of these pathways in yeast has been a valuable help in understanding the intricate mechanisms of cell death in higher eukaryotes, and of severe human diseases associated with mitochondria-dependent apoptosis. In addition, the absence of obvious orthologues of mammalian apoptotic regulators, namely of the Bcl-2 family, favours the use of yeast to assess the function of such proteins. In conclusion, yeast with its distinctive ability to survive without respiration-competent mitochondria is a powerful model to study the involvement of mitochondria and mitochondria interacting proteins in cell death.
    Full-text · Article · Aug 2008 · Biochimica et Biophysica Acta
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