| 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. |
- Ferreira, Daniela, et al.
(författare)
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Transcription and regulation of the hydrogenase(s) accessory genes, hypFCDEAB, in the cyanobacterium Lyngbya majuscula CCAP 1446/4
- 2007
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Ingår i: Archives of Microbiology. - : Springer Science and Business Media LLC. - 0302-8933 .- 1432-072X. ; 188:6, s. 609-617
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Tidskriftsartikel (refereegranskat)abstract
- Lyngbya majuscula CCAP 1446/4 is a filamentous cyanobacterium possessing both an uptake and a bi-directional hydrogenase. The presence of a single copy of the hyp operon in the cyanobacterial genomes suggests that these accessory genes might be responsible for the maturation of both hydrogenases. We investigated the concomitant transcription of hypFCDEAB with the hydrogenases structural genes-hup and hox. RT-PCRs performed with L. majuscula cells grown under different physiological conditions showed a substantial decrease in the relative amount of hupL transcript under non-N-2-fixing conditions. In contrast, no significant differences were observed for the transcript levels of hypFCDEAB in all conditions tested, while minor fluctuations could be discerned for hoxH. Previously, it was demonstrated that the transcriptional regulators NtcA and LexA interact with the promoter regions of hup and hox, respectively, and that putative binding sites for both proteins are present in the hyp promoter of L. majuscula. Therefore, a putative involvement of NtcA and LexA in the regulation of the hyp transcription was investigated. Electrophoretic mobility shift assays resulted in NtcA or LexA-bound retarded fragments, suggesting the involvement of these proteins in the transcriptional regulation of hypFCDEAB.
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| 3. |
- 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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| 4. |
- Santos, Catarina L, et al.
(författare)
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Modulation of Frankia alni ACN14a oxidative stress response: activity, expression and phylogeny of catalases
- 2007
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 130, s. 454-463
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Tidskriftsartikel (refereegranskat)abstract
- The finding that an oxidative burst was a general phenomenon in the response of hosts challenged by various symbiotic or pathogenic microbes has stimulated increasing interest in investigating the enzymology of antioxidant protection in bacteria. The question of whether the antioxidant mechanisms have been a decisive evolutionary driving force for the nitrogen-fixing microsymbiont Frankia spp. is still open. In this study, Frankia alni strain ACN14a, which is a mid-range infective strain, was used as a model to explore the basal oxidative stress response in terms of enzymatic activity, relative expression and phylogeny. Non-denaturing polyacrylamide gels stained for catalatic activity revealed the presence of two monofunctional catalases KatA and KatB (EC number 1.11.1.6), which activity was shown to increase when the cells were challenged with the oxidants H2O2 and methyl viologen. Real-time RT-PCR targeting the two genes showed a consistent increase in the number of transcripts when the RNA was extracted from oxidative stress-induced cells. Comparison between the expression and the activity data suggests that posttranscriptional mechanisms might be involved in the regulation of catalases in F. alni. Furthermore, upstream of katA, a fur gene coding for a ferric uptake regulator was found, forming a gene pair that functionally resembles the conserved actinobacterial synton fur–katG, which contains a gene coding for a catalase–peroxidase. Phylogenetic analysis of the F. alni fur–katA synton suggests that this genomic organization was the result of genome reshuffling events.
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