Project description:The goal of the project was to study the effects on transctiption and mRNA stability after iron depletion. We analyzed the effect of iron depletion caused by 100 μM of the Fe2+-specific chelator bathophenanthroline disulfonic acid (BPS) on the transcription rates, mRNA stabilities and mRNA levels by doing Genomic Run-On (GRO) experiments at 0, 10, 30, 90, 180 and 360 minutes after iron limitation.
Project description:The budding yeast S. cerevisiae responds to depletion of iron in the environment by activating Aft1p, the major iron-dependent transcription factor, and by transcribing systems involved in the uptake of iron. Here we have studied the transcriptional response to iron deprivation, and have identified new Aft1p target genes. We find that other metabolic pathways are regulated by iron: biotin uptake and biosynthesis, nitrogen assimilation, and purine biosynthesis. Two enzymes active in these pathways, biotin synthase and glutamate synthase, require an iron-sulfur cluster for activity. Iron deprivation activates transcription of the biotin importer and simultaneously represses transcription of the entire biotin biosynthetic pathway. Multiple genes involved in nitrogen assimilation and amino acid metabolism are induced by iron deprivation, while glutamate synthase, a key enzyme in nitrogen assimilation, is repressed. A CGG palindrome within the promoter of glutamate synthase confers iron-regulated expression, suggesting control by a transcription factor of the binuclear zinc cluster family. We provide evidence that yeast subjected to iron deprivation undergo a transcriptional remodeling, resulting in a shift from iron-dependent to parallel, but iron-independent, metabolic pathways. A dose response design type examines the relationship between the size of the administered dose and the extent of the response of the organism(s). Keywords: dose_response_design
Project description:The budding yeast S. cerevisiae responds to depletion of iron in the environment by activating Aft1p, the major iron-dependent transcription factor, and by transcribing systems involved in the uptake of iron. Here we have studied the transcriptional response to iron deprivation, and have identified new Aft1p target genes. We find that other metabolic pathways are regulated by iron: biotin uptake and biosynthesis, nitrogen assimilation, and purine biosynthesis. Two enzymes active in these pathways, biotin synthase and glutamate synthase, require an iron-sulfur cluster for activity. Iron deprivation activates transcription of the biotin importer and simultaneously represses transcription of the entire biotin biosynthetic pathway. Multiple genes involved in nitrogen assimilation and amino acid metabolism are induced by iron deprivation, while glutamate synthase, a key enzyme in nitrogen assimilation, is repressed. A CGG palindrome within the promoter of glutamate synthase confers iron-regulated expression, suggesting control by a transcription factor of the binuclear zinc cluster family. We provide evidence that yeast subjected to iron deprivation undergo a transcriptional remodeling, resulting in a shift from iron-dependent to parallel, but iron-independent, metabolic pathways. A dose response design type examines the relationship between the size of the administered dose and the extent of the response of the organism(s). Using regression correlation
Project description:Analysis of iron-regulated gene expression in Saccharomyces cerevisiae using cDNA microarrays has identified three putative cell wall proteins that are directly regulated by Aft1p, the major iron-dependent transcription factor in yeast. FIT1, FIT2, and FIT3 (for facilitator of iron transport) were more highly expressed in strains grown in low concentrations of iron and in strains in which AFT1-1(up), a constitutively active allele of AFT1, was expressed. Northern blot analysis confirmed that FIT1, FIT2, and FIT3 mRNA transcript levels were increased 60-230-fold in response to iron deprivation in an Aft1p-dependent manner. Fit1p was localized exclusively to the cell wall by indirect immunofluorescence. Deletion of the FIT genes, individually or in combination, resulted in diminished uptake of iron bound to the siderophores ferrioxamine B and ferrichrome, without diminishing the uptake of ferric iron salts, or the siderophores triacetylfusarinine C and enterobactin. FIT-deletion strains exhibited increased expression of Aft1p target genes as measured by a FET3-lacZ reporter gene or by Arn1p Western blotting, indicating that cells respond to the absence of FIT genes by up-regulating systems of iron uptake. Aft1p activation in FIT-deleted strains occurred when either ferrichrome or ferric salts were used as sources of iron during growth, suggesting that the FIT genes enhance uptake of iron from both sources. Enzymatic digestion of the cell wall resulted in the release of significant amounts of iron from cells, and the relative quantity of iron released was reduced in FIT-deletion strains. Fit1p, Fit2p, and Fit3p may function by increasing the amount of iron associated with the cell wall and periplasmic space. Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. Keywords: Logical Set
Project description:Iron homeostasis in the yeast Saccharomyces cerevisiae is regulated at the transcriptional level by Aft1p, which activates the expression of its target genes in response to low-iron conditions. The yeast genome contains a paralog of AFT1, which has been designated AFT2. To establish whether AFT1 and AFT2 have overlapping functions, a mutant containing a double aft1aft2 deletion was generated. Growth assays established that the single aft2 strain exhibited no iron-dependent phenotype. However, the double-mutant aft1aft2 strain was more sensitive to low-iron growth conditions than the single-mutant aft1 strain. A mutant allele of AFT2 (AFT2-1up), or overexpression of the wild-type AFT2 gene, led to partial complementation of the respiratory- deficient phenotype of the aft1 strain. The AFT2-1up allele also increased the uptake of 59Fe in an aft1 strain. DNA microarrays were used to identify genes regulated by AFT2. Some of the AFT2-regulated genes are known to be regulated by Aft1p; however, AFT2-1up-dependent activation was independent of Aft1p. The kinetics of induction of two genes activated by the AFT2-1up allele are consistent with Aft2p acting as a direct transcriptional factor. Truncated forms of Aft1p and Aft2p bound to a DNA duplex containing the Aft1p binding site in vitro. The wild-type allele of AFT2 activated transcription in response to growth under low-iron conditions. Together, these data suggest that yeast has a second regulatory pathway for the iron regulon, with AFT1 and AFT2 playing partially redundant roles. Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. Keywords: Logical Set
Project description:Iron-resistant Saccharomyces cerevisiae mutant was obtained by evolutionary engineering selection strategy. The mutant obtained M-bM-^@M-^\M8FEM-bM-^@M-^] is much more resistant to iron stress than the reference strain which was used to select this mutant. Mutant can resist up to 35mM Iron* stress whereas the reference strain cannot. Whole-genome microarray analysis might be promising to identify the iron resistance mechanisms and stress response upon high levels of iron in the yeast cells. Iron-resistant mutant is also cross resistant to Cobalt, Chromium and Nickel but sensitive to Zinc. * refers to [NH4]2[Fe][SO4]2 and FeCl2. The reference Saccharomyces cerevisiae strain and the iron-resistant mutant were grown in minimal medium to an Optical Density (OD600) of 1.00 which correspond to the logarithmic growth phase of the yeast cells. Cultures were harvested and whole RNA isolation was carried out. The experiment was repeated three times.
Project description:Iron-resistant Saccharomyces cerevisiae mutant was obtained by evolutionary engineering selection strategy. The mutant obtained “M8FE” is much more resistant to iron stress than the reference strain which was used to select this mutant. Mutant can resist up to 35mM Iron* stress whereas the reference strain cannot. Whole-genome microarray analysis might be promising to identify the iron resistance mechanisms and stress response upon high levels of iron in the yeast cells. Iron-resistant mutant is also cross resistant to Cobalt, Chromium and Nickel but sensitive to Zinc. * refers to [NH4]2[Fe][SO4]2 and FeCl2.
Project description:Iron homeostasis in the yeast Saccharomyces cerevisiae is regulated at the transcriptional level by Aft1p, which activates the expression of its target genes in response to low-iron conditions. The yeast genome contains a paralog of AFT1, which has been designated AFT2. To establish whether AFT1 and AFT2 have overlapping functions, a mutant containing a double aft1aft2 deletion was generated. Growth assays established that the single aft2 strain exhibited no iron-dependent phenotype. However, the double-mutant aft1aft2 strain was more sensitive to low-iron growth conditions than the single-mutant aft1 strain. A mutant allele of AFT2 (AFT2-1up), or overexpression of the wild-type AFT2 gene, led to partial complementation of the respiratory- deficient phenotype of the aft1 strain. The AFT2-1up allele also increased the uptake of 59Fe in an aft1 strain. DNA microarrays were used to identify genes regulated by AFT2. Some of the AFT2-regulated genes are known to be regulated by Aft1p; however, AFT2-1up-dependent activation was independent of Aft1p. The kinetics of induction of two genes activated by the AFT2-1up allele are consistent with Aft2p acting as a direct transcriptional factor. Truncated forms of Aft1p and Aft2p bound to a DNA duplex containing the Aft1p binding site in vitro. The wild-type allele of AFT2 activated transcription in response to growth under low-iron conditions. Together, these data suggest that yeast has a second regulatory pathway for the iron regulon, with AFT1 and AFT2 playing partially redundant roles. Set of arrays organized by shared biological context, such as organism, tumors types, processes, etc. Computed
Project description:V. vulnificus is a marine bacteria that causes diseases in both mammals and fish. In both hosts, the iron concentration represents a key factor that greatly influences the virulence of this bacterium. To further define the gene repertoire that is regulated by iron concentration and Fur protein (the main transcriptional regulator in response to iron concentration) in V. vulnificus, we obtained a mutant in Fur and used DNA microarray technology to monitor the expression of the entire gene repertoire in response to iron. Global transcriptomic response was reconstructed by comparing the transcriptional profiles of the wild-type (R99) and Fur mutant strains in poor and rich iron conditions. To identify the genes that were under control of Fur, we compared the transcriptomic profile of the wild-type strain with the profile of a mutant strain in Fur protein; in contrast, to identify the genes that were under control of iron, we compared the transcriptomic profile of the wild-type strain grown in iron-rich conditions with the profile of the wild-type strain grown in iron-restricted conditions. For each one of the four samples, three replicates were performed, and RNA was sampled in the mid-log phase of growth (wild-type, 6h; Fur mutant, 6h; wild-type+iron, 5h; wild-type-iron,9h).