| 1. |
- Almeida, Teresa, et al.
(författare)
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Isc1p plays a key role in hydrogen peroxide resistance and chronological lifespan through modulation of iron levels and apoptosis.
- 2008
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Ingår i: Molecular biology of the cell. - 1939-4586. ; 19:3, s. 865-76
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Tidskriftsartikel (refereegranskat)abstract
- The inositolphosphosphingolipid phospholipase C (Isc1p) of Saccharomyces cerevisiae belongs to the family of neutral sphingomyelinases that generates the bioactive sphingolipid ceramide. In this work the role of Isc1p in oxidative stress resistance and chronological lifespan was investigated. Loss of Isc1p resulted in a higher sensitivity to hydrogen peroxide that was associated with an increase in oxidative stress markers, namely intracellular oxidation, protein carbonylation, and lipid peroxidation. Microarray analysis showed that Isc1p deficiency up-regulated the iron regulon leading to increased levels of iron, which is known to catalyze the production of the highly reactive hydroxyl radicals via the Fenton reaction. In agreement, iron chelation suppressed hydrogen peroxide sensitivity of isc1Delta mutants. Cells lacking Isc1p also displayed a shortened chronological lifespan associated with oxidative stress markers and aging of parental cells was correlated with a decrease in Isc1p activity. The analysis of DNA fragmentation and caspase-like activity showed that Isc1p deficiency increased apoptotic cell death associated with oxidative stress and aging. Furthermore, deletion of Yca1p metacaspase suppressed the oxidative stress sensitivity and premature aging phenotypes of isc1Delta mutants. These results indicate that Isc1p plays an important role in the regulation of cellular redox homeostasis, through modulation of iron levels, and of apoptosis.
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| 2. |
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| 3. |
- Ericsson, Abraham, 1973, et al.
(författare)
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Case study in systematic modelling: thiamine uptake in the yeast Saccharomyces cerevisiae.
- 2008
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Ingår i: Essays in biochemistry. - 0071-1365. ; 45, s. 135-46
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, with important advances in molecular biology, experimental and measurement technologies, it has become possible to generate the quantitative data that are needed for building mathematical models of complex biochemical processes. Cartoon-like diagrams of biological pathways can be turned into dynamical models, allowing simulation and analysis to gain an insight into the underlying control mechanisms and the behaviour of the overall system. This kind of system-level understanding has not been reachable from the study of the components of pathways in isolation. However, mathematical modelling does not only integrate the available knowledge about a certain system with newly generated experimental results. During the process of modelling, questions need to be addressed that lead to an increased quantitative understanding of the system. Models can be used to optimize experimental approaches and protocols and to test different hypotheses about the underlying biological mechanisms. Finally, a validated mathematical model can be used to perform in silico experiments that might be hard or impossible to do in the laboratory. In this chapter we present a case study of a systematic modelling approach applied to the thiamine uptake system of the yeast Saccharomyces cerevisiae. This example is part of our broader effort to model the whole of thiamine metabolism in yeast, which involves several additional processes such as thiamine utilization, biosynthesis and gene regulation. Our main goal is to describe how systematic modelling has improved the knowledge about the system under study.
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| 4. |
- Marques, Marta, et al.
(författare)
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The Pep4p vacuolar proteinase contributes to the turnover of oxidized proteins but PEP4 overexpression is not sufficient to increase chronological lifespan in Saccharomyces cerevisiae
- 2006
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Ingår i: Microbiology. - : Microbiology Society. - 1350-0872 .- 1465-2080. ; 152:12, s. 3595-3605
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Tidskriftsartikel (refereegranskat)abstract
- Turnover of damaged molecules is considered to play a key role in housekeeping of cells exposed to oxidative stress, and during the progress of ageing. In this work, global changes in the transcriptome were analysed during recovery of yeast cells after H2O2 stress. Regarding induced genes, those associated with protein fate were the most significantly over-represented. In addition to genes encoding subunits of the 20S proteasome, genes related to vacuolar proteolysis (PEP4 and LAP4), protein sorting into the vacuole, and vacuolar fusion were found to be induced. The upregulation of PEP4 gene expression was associated with an increase in Pep4p activity. The induction of genes related to proteolysis was correlated with an increased protein turnover after H2O2-induced oxidation. Furthermore, protein degradation and the removal of oxidized proteins decreased in Pep4p-deficient cells. Pep4p activity also increased during chronological ageing, and cells lacking Pep4p displayed a shortened lifespan associated with higher levels of carbonylated proteins. PEP4 overexpression prevented the accumulation of oxidized proteins, but did not increase lifespan. These results indicate that Pep4p is important for protein turnover after oxidative damage; however, increased removal of oxidized proteins is not sufficient to enhance lifespan
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| 5. |
- Mojzita, Dominik, 1977, et al.
(författare)
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Pdc2 coordinates expression of the THI regulon in the yeast Saccharomyces cerevisiae
- 2006
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Ingår i: Molecular Genetics and Genomics. - : Springer Science and Business Media LLC. - 1617-4615 .- 1617-4623. ; 276:2, s. 147-161
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Tidskriftsartikel (refereegranskat)abstract
- Coordination of gene expression in response to different metabolic signals is crucial for cellular homeostasis. In this work, we addressed the role of Pdc2 in the coordinated control of biosynthesis and demand of an essential metabolic cofactor, thiaminediphosphate (ThDP). The DNA binding protein Pdc2 was initially identified as a regulator of the genes PDC1 and PDC5, which encode isoforms of the glycolytic enzyme pyruvate decarboxylase (Pdc). The Pdc2 has also been implicated as a regulator of genes encoding enzymes in ThDP metabolism. The ThDP is the cofactor of Pdc. Using global and gene-specific expression analysis, we show that Pdc2 is required for the upregulation of all genes controlled by thiamine availability. The Pdc2 seems to act together with Thi2, a known transcriptional regulator of THI genes. The requirement for these two factors differs in a gene-specific manner. While the Thi2, in conjunction with Thi3, seems to control expression of THI genes with respect to thiamine availability, the Pdc2 may link the ThDP demand to carbon source availability. Interestingly, the enzymes Pdc1 and Pdc5 are enriched in the nucleus. Both are known to affect gene expression in an autoregulatory mechanism and expression of both is regulated by glucose and Pdc2, further pointing to a role of Pdc2 in coordinating different metabolic signals. Our analysis helps to further define the THI regulon and hence the spectrum of genes/proteins involved in the ThDP homeostasis. In particular, we identify novel proteins putatively involved in thiamine and/or ThDP transport across the plasma and the mitochondrial membrane. In conclusion, the THI regulon is the most interesting system to study principles of genes expression and metabolic coordination and deserves further attention.
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