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FEMS Microbiology Reviews Mar 2014Although a budding yeast culture can be propagated eternally, individual yeast cells age and eventually die. The detailed knowledge of this unicellular eukaryotic... (Review)
Review
Although a budding yeast culture can be propagated eternally, individual yeast cells age and eventually die. The detailed knowledge of this unicellular eukaryotic species as well as the powerful tools developed to study its physiology makes budding yeast an ideal model organism to study the mechanisms involved in aging. Considering both detrimental and positive aspects of age, we review changes occurring during aging both at the whole-cell level and at the intracellular level. The possible mechanisms allowing old cells to produce rejuvenated progeny are described in terms of accumulation and inheritance of aging factors. Based on the dynamic changes associated with age, we distinguish different stages of age: early age, during which changes do not impair cell growth; intermediate age, during which aging factors start to accumulate; and late age, which corresponds to the last divisions before death. For each aging factor, we examine its asymmetric segregation and whether it plays a causal role in aging. Using the example of caloric restriction, we describe how the aging process can be modulated at different levels and how changes in different organelles might interplay with each other. Finally, we discuss the beneficial aspects that might be associated with age.
Topics: Aging; Caloric Restriction; Models, Biological; Organelles; Saccharomyces cerevisiae
PubMed: 24484434
DOI: 10.1111/1574-6976.12060 -
Microbiological Research Aug 2015Ribosomal proteins (RPs), are essential components of the ribosomes, the molecular machines that turn mRNA blueprints into proteins, as they serve to stabilize the... (Review)
Review
Ribosomal proteins (RPs), are essential components of the ribosomes, the molecular machines that turn mRNA blueprints into proteins, as they serve to stabilize the structure of the rRNA, thus improving protein biosynthesis. In addition, growing evidence suggests that RPs can function in other cellular roles. In the present review, we summarize several potential extra-ribosomal functions of RPs in ribosomal biogenesis, transcription activity, translation process, DNA repair, replicative life span, adhesive growth, and morphological transformation in Saccharomyces cerevisiae. However, the future in-depth studies are needed to identify these novel secondary functions of RPs in S. cerevisiae.
Topics: Cell Adhesion; DNA Repair; Metabolic Networks and Pathways; Protein Biosynthesis; Ribosomal Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Transcription, Genetic
PubMed: 26211963
DOI: 10.1016/j.micres.2015.05.004 -
Microbiology and Molecular Biology... Jun 2004The cells of organisms as diverse as bacteria and humans can enter stable, nonproliferating quiescent states. Quiescent cells of eukaryotic and prokaryotic... (Review)
Review
The cells of organisms as diverse as bacteria and humans can enter stable, nonproliferating quiescent states. Quiescent cells of eukaryotic and prokaryotic microorganisms can survive for long periods without nutrients. This alternative state of cells is still poorly understood, yet much benefit is to be gained by understanding it both scientifically and with reference to human health. Here, we review our knowledge of one "model" quiescent cell population, in cultures of yeast grown to stationary phase in rich media. We outline the importance of understanding quiescence, summarize the properties of quiescent yeast cells, and clarify some definitions of the state. We propose that the processes by which a cell enters into, maintains viability in, and exits from quiescence are best viewed as an environmentally triggered cycle: the cell quiescence cycle. We synthesize what is known about the mechanisms by which yeast cells enter into quiescence, including the possible roles of the protein kinase A, TOR, protein kinase C, and Snf1p pathways. We also discuss selected mechanisms by which quiescent cells maintain viability, including metabolism, protein modification, and redox homeostasis. Finally, we outline what is known about the process by which cells exit from quiescence when nutrients again become available.
Topics: Cell Survival; Culture Media; Gene Expression Regulation, Fungal; Genes, Fungal; Models, Biological; Mutation; Resting Phase, Cell Cycle; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Signal Transduction; Transcription, Genetic
PubMed: 15187181
DOI: 10.1128/MMBR.68.2.187-206.2004 -
Biogerontology Aug 2017Experimental gerontology is based on the fundamental assumption that the aging process has a universal character and that the mechanisms of aging are well-conserved... (Review)
Review
Experimental gerontology is based on the fundamental assumption that the aging process has a universal character and that the mechanisms of aging are well-conserved among living things. The consequence of this assumption is the use of various organisms, including unicellular yeast Saccharomyces cerevisiae, as models in gerontology, and direct extrapolation of the conclusions drawn from the studies carried on these organisms to human beings. However, numerous arguments suggest that aging is not universal and its mechanisms are not conserved in a wide range of species. Instead, senescence can be treated as a side effect of the evolution of specific features for systematic group, unrelated to the passage of time. Hence, depending on the properties of the group, the senescence and proximal causes of death could have a diverse nature. We postulate that the selection of a model organism to explain the mechanism of human aging and human longevity should be preceded by the analysis of its potential to extrapolate the results to a wide group of organisms. Considering that gerontology is a human-oriented discipline and that aging involves complex, systemic changes affecting the entire organism, the object of experimental studies should be animals which are closest relatives of human beings in evolutionary terms, rather than lower organisms, which do not have sufficient complexity in terms of tissues and organ structures.
Topics: Animal Testing Alternatives; Animals; Biomedical Research; Cellular Senescence; Geriatrics; Humans; Longevity; Models, Animal; Saccharomyces cerevisiae; Species Specificity
PubMed: 28573416
DOI: 10.1007/s10522-017-9712-x -
Current Opinion in Microbiology Apr 2008The yeast Saccharomyces cerevisiae senses and responds to nutrients by adapting its growth rate and undergoing morphogenic transitions to ensure survival. The Tor... (Review)
Review
The yeast Saccharomyces cerevisiae senses and responds to nutrients by adapting its growth rate and undergoing morphogenic transitions to ensure survival. The Tor pathway is a major integrator of nutrient-derived signals that in coordination with other signaling pathways orchestrates cell growth. Recent advances have identified novel Tor kinase substrates and established the protein trafficking membranous network and the nucleus as platforms for Tor signaling. These and other recent findings delineate distinct signaling branches emanating from membrane-associated Tor complexes to control cell growth.
Topics: Gene Expression Regulation, Fungal; Protein Serine-Threonine Kinases; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Signal Transduction
PubMed: 18396450
DOI: 10.1016/j.mib.2008.02.013 -
Microbiological Reviews Jun 1993Growth and proliferation of microorganisms such as the yeast Saccharomyces cerevisiae are controlled in part by the availability of nutrients. When proliferating yeast... (Review)
Review
Growth and proliferation of microorganisms such as the yeast Saccharomyces cerevisiae are controlled in part by the availability of nutrients. When proliferating yeast cells exhaust available nutrients, they enter a stationary phase characterized by cell cycle arrest and specific physiological, biochemical, and morphological changes. These changes include thickening of the cell wall, accumulation of reserve carbohydrates, and acquisition of thermotolerance. Recent characterization of mutant cells that are conditionally defective only for the resumption of proliferation from stationary phase provides evidence that stationary phase is a unique developmental state. Strains with mutations affecting entry into and survival during stationary phase have also been isolated, and the mutations have been shown to affect at least seven different cellular processes: (i) signal transduction, (ii) protein synthesis, (iii) protein N-terminal acetylation, (iv) protein turnover, (v) protein secretion, (vi) membrane biosynthesis, and (vii) cell polarity. The exact nature of the relationship between these processes and survival during stationary phase remains to be elucidated. We propose that cell cycle arrest coordinated with the ability to remain viable in the absence of additional nutrients provides a good operational definition of starvation-induced stationary phase.
Topics: Cyclic AMP; Fungal Proteins; Interphase; Protein Biosynthesis; Saccharomyces cerevisiae; Signal Transduction; Transcription, Genetic
PubMed: 8393130
DOI: 10.1128/mr.57.2.383-401.1993 -
DNA Repair Sep 2009The DNA damage and replication checkpoints are believed to primarily slow the progression of the cell cycle to allow DNA repair to occur. Here we summarize known aspects... (Review)
Review
The DNA damage and replication checkpoints are believed to primarily slow the progression of the cell cycle to allow DNA repair to occur. Here we summarize known aspects of the Saccharomyces cerevisiae checkpoints including how these responses are integrated into downstream effects on the cell cycle, chromatin, DNA repair, and cytoplasmic targets. Analysis of the transcriptional response demonstrates that it is far more complex and less relevant to the repair of DNA damage than the bacterial SOS response. We also address more speculative questions regarding potential roles of the checkpoint during the normal S-phase and how current evidence hints at a checkpoint activation mechanism mediated by positive feedback that amplifies initial damage signals above a minimum threshold.
Topics: Cell Cycle; DNA Damage; DNA Replication; Feedback, Physiological; Saccharomyces cerevisiae
PubMed: 19477695
DOI: 10.1016/j.dnarep.2009.04.021 -
FEBS Letters Jul 2019In yeasts, the plasma membrane forms the barrier that protects the cell from the outside world, but also gathers and keeps valuable compounds inside. Although it is... (Review)
Review
In yeasts, the plasma membrane forms the barrier that protects the cell from the outside world, but also gathers and keeps valuable compounds inside. Although it is often suggested that hydrophobic molecules surpass this checkpoint by simple diffusion, it now becomes evident that protein-facilitated transport mechanisms allow for selective import and export of triglycerides, fatty acids, alkanes, and sterols in yeasts. During biomass production, hydrophobic carbon sources enter and exit the cell efficiently in a strictly regulated manner that helps avoid toxicity. Furthermore, various molecules, such as yeast pheromones, secondary metabolites and xenobiotics, are exported to ensure cell-cell communication, or increase chances of survival. This review summarizes the current knowledge on how hydrophobic compounds interact with protein-facilitated transport systems on the plasma membrane and how selective import and export across the yeast plasma membrane is achieved. Both the model organism Saccharomyces cerevisiae, as well as unconventional yeasts are discussed.
Topics: Adaptation, Physiological; Biological Transport; Cell Membrane; Hydrophobic and Hydrophilic Interactions; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins
PubMed: 31166012
DOI: 10.1002/1873-3468.13469 -
Journal of Genetics and Genomics = Yi... Jun 2016Compartmentation via filamentation has recently emerged as a novel mechanism for metabolic regulation. In order to identify filament-forming metabolic enzymes...
Compartmentation via filamentation has recently emerged as a novel mechanism for metabolic regulation. In order to identify filament-forming metabolic enzymes systematically, we performed a genome-wide screening of all strains available from an open reading frame-GFP collection in Saccharomyces cerevisiae. We discovered nine novel filament-forming proteins and also confirmed those identified previously. From the 4159 strains, we found 23 proteins, mostly metabolic enzymes, which are capable of forming filaments in vivo. In silico protein-protein interaction analysis suggests that these filament-forming proteins can be clustered into several groups, including translational initiation machinery and glucose and nitrogen metabolic pathways. Using glutamine-utilising enzymes as examples, we found that the culture conditions affect the occurrence and length of the metabolic filaments. Furthermore, we found that two CTP synthases (Ura7p and Ura8p) and two asparagine synthetases (Asn1p and Asn2p) form filaments both in the cytoplasm and in the nucleus. Live imaging analyses suggest that metabolic filaments undergo sub-diffusion. Taken together, our genome-wide screening identifies additional filament-forming proteins in S. cerevisiae and suggests that filamentation of metabolic enzymes is more general than currently appreciated.
Topics: Cell Nucleus; Cytoskeleton; Genomics; Saccharomyces cerevisiae
PubMed: 27312010
DOI: 10.1016/j.jgg.2016.03.008 -
Cell Cycle (Georgetown, Tex.) Apr 2017
Topics: Models, Biological; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Small Ubiquitin-Related Modifier Proteins; Transcription, Genetic
PubMed: 28278057
DOI: 10.1080/15384101.2017.1294945