Global view on the metabolism of RNA poly(A) tails in yeast Saccharomyces cerevisiae.
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ABSTRACT:
SUBMITTER: Tudek A
PROVIDER: S-EPMC8367983 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundProteins in organisms, rather than act alone, usually form protein complexes to perform cellular functions. We analyze the topological network structure of protein complexes and their component proteins in the budding yeast in terms of the bipartite network and its projections, where the complexes and proteins are its two distinct components. Compared to conventional protein-protein interaction networks, the networks from the protein complexes show more homogeneous structures than those of the binary protein interactions, implying the formation of complexes that cause a relatively more uniform number of interaction partners. In addition, we suggest a new optimization method to determine the abundance and function of protein complexes, based on the information of their global organization. Estimating abundance and biological functions is of great importance for many researches, by providing a quantitative description of cell behaviors, instead of just a "catalogues" of the lists of protein interactions.ResultsWith our new optimization method, we present genome-wide assignments of abundance and biological functions for complexes, as well as previously unknown abundance and functions of proteins, which can provide significant information for further investigations in proteomics. It is strongly supported by a number of biologically relevant examples, such as the relationship between the cytoskeleton proteins and signal transduction and the metabolic enzyme Eno2's involvement in the cell division process.ConclusionsWe believe that our methods and findings are applicable not only to the specific area of proteomics, but also to much broader areas of systems biology with the concept of optimization principle.
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Project description:The yeast MTO1 gene encodes an evolutionarily conserved protein for the biosynthesis of the 5-carboxymethylaminomethyl group of cmnm(5)s(2)U in the wobble position of mitochondrial tRNA. However, mto1 null mutant expressed the respiratory deficient phenotype only when coupled with the C1409G mutation of mitochondrial 15S rRNA. To further understand the role of MTO1 in mitochondrial RNA metabolism, the yeast mto1 null mutants carrying either wild-type (P(S)) or 15S rRNA C1409G allele (P(R)) have been characterized by examining the steady-state levels, aminoacylation capacity of mitochondrial tRNA, mitochondrial gene expression and petite formation. The steady-state levels of tRNA(Lys), tRNA(Glu), tRNA(Gln), tRNA(Leu), tRNA(Gly), tRNA(Arg) and tRNA(Phe) were decreased significantly while those of tRNA(Met) and tRNA(His) were not affected in the mto1 strains carrying the P(S) allele. Strikingly, the combination of the mto1 and C1409G mutations gave rise to the synthetic phenotype for some of the tRNAs, especially in tRNA(Lys), tRNA(Met) and tRNA(Phe). Furthermore, the mto1 strains exhibited a marked reduction in the aminoacylation levels of mitochondrial tRNA(Lys), tRNA(Leu), tRNA(Arg) but almost no effect in those of tRNA(His). In addition, the steady-state levels of mitochondrial COX1, COX2, COX3, ATP6 and ATP9 mRNA were markedly decreased in mto1 strains. These data strongly indicate that unmodified tRNA caused by the deletion of MTO1 gene caused the instability of mitochondrial tRNAs and mRNAs and an impairment of aminoacylation of mitochondrial tRNAs. Consequently, the deletion of MTO1 gene acts in synergy with the 15S rRNA C1409G mutation, leading to the loss of COX1 synthesis and subsequent respiratory deficient phenotype.
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Project description:Saccharomyces cerevisiae is a Crabtree-positive eukaryal model organism. It is believed that the Crabtree effect has evolved as a competition mechanism by allowing for rapid growth and production of ethanol at aerobic glucose excess conditions. This inherent property of yeast metabolism and the multiple mechanisms underlying it require a global rewiring of the entire metabolic network to abolish the Crabtree effect. Through rational engineering of pyruvate metabolism combined with adaptive laboratory evolution (ALE), we demonstrate that it is possible to obtain such a global rewiring and hereby turn S. cerevisiae into a Crabtree-negative yeast. Using integrated systems biology analysis, we identify that the global rewiring of cellular metabolism is accomplished through a mutation in the RNA polymerase II mediator complex, which is also observed in cancer cells expressing the Warburg effect.
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Project description:BackgroundThe size of the phenotypic effect of a gene has been thoroughly investigated in terms of fitness and specific morphological traits in the budding yeast Saccharomyces cerevisiae, but little is known about gross morphological abnormalities.ResultsWe identified 1126 holistic morphological effectors that cause severe gross morphological abnormality when deleted, and 2241 specific morphological effectors with weak holistic effects but distinctive effects on yeast morphology. Holistic effectors fell into many gene function categories and acted as network hubs, affecting a large number of morphological traits, interacting with a large number of genes, and facilitating high protein expression. Holistic morphological abnormality was useful for estimating the importance of a gene to morphology. The contribution of gene importance to fitness and morphology could be used to efficiently classify genes into functional groups.ConclusionHolistic morphological abnormality can be used as a reproducible and reliable gene feature for high-dimensional morphological phenotyping. It can be used in many functional genomic applications.
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Project description:As we are moving into the post genome-sequencing era, various high-throughput experimental techniques have been developed to characterize biological systems on the genomic scale. Discovering new biological knowledge from the high-throughput biological data is a major challenge to bioinformatics today. To address this challenge, we developed a Bayesian statistical method together with Boltzmann machine and simulated annealing for protein functional annotation in the yeast Saccharomyces cerevisiae through integrating various high-throughput biological data, including yeast two-hybrid data, protein complexes and microarray gene expression profiles. In our approach, we quantified the relationship between functional similarity and high-throughput data, and coded the relationship into 'functional linkage graph', where each node represents one protein and the weight of each edge is characterized by the Bayesian probability of function similarity between two proteins. We also integrated the evolution information and protein subcellular localization information into the prediction. Based on our method, 1802 out of 2280 unannotated proteins in yeast were assigned functions systematically.
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Project description:The U3 small nucleolar RNA participates in early events of eukaryotic pre-rRNA cleavage and is essential for formation of 18S rRNA. Using an in vivo system, we have developed a functional map of the U3 small nucleolar RNA from Saccharomyces cerevisiae. The test strain features a galactose-dependent U3 gene in the chromosome and a plasmid-encoded allele with a unique hybridization tag. Effects of mutations on U3 production were analyzed by evaluating RNA levels in cells grown on galactose medium, and effects on U3 function were assessed by growing cells on glucose medium. The major findings are as follows: (i) boxes C' and D and flanking helices are critical for U3 accumulation; (ii) boxes B and C are not essential for U3 production but are important for function, most likely due to binding of a trans-acting factor(s); (iii) the 5' portion of U3 is required for function but not stability; and, (iv) strikingly, the nonconserved hairpins 2, 3, and 4, which account for 50% of the molecule, are not required for accumulation or function.
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Project description:The mechanism of mRNA export is a complex issue central to cellular physiology. We characterized previously yeast Gle1p, a protein with a leucine-rich (LR) nuclear export sequence (NES) that is essential for poly(A)+ RNA export in Saccharomyces cerevisiae. To characterize elements of the vertebrate mRNA export pathway, we identified a human homologue of yeast Gle1p and analyzed its function in mammalian cells. hGLE1 encodes a predicted 75-kDa polypeptide with high sequence homology to yeast Gle1p, but hGle1p does not contain a sequence motif matching any of the previously characterized NESs. hGLE1 can complement a yeast gle1 temperature-sensitive export mutant only if a LR-NES is inserted into it. To determine whether hGle1p played a role in nuclear export, anti-hGle1p antibodies were microinjected into HeLa cells. In situ hybridization of injected cells showed that poly(A)+ RNA export was inhibited. In contrast, there was no effect on the nuclear import of a glucocorticoid receptor reporter. We conclude that hGle1p functions in poly(A)+ RNA export, and that human cells facilitate such export with a factor similar to yeast but without a recognizable LR-NES. With hGle1p localized at the nuclear pore complexes, hGle1p is positioned to act at a terminal step in the export of mature RNA messages to the cytoplasm.
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Project description:We compared the transcriptomes of Saccharomyces cerevisiae cells growing under steady-state conditions on 21 unique sources of nitrogen. We found 506 genes differentially regulated by nitrogen and estimated the activation degrees of all identified nitrogen-responding transcriptional controls according to the nitrogen source. One main group of nitrogenous compounds supports fast growth and a highly active nitrogen catabolite repression (NCR) control. Catabolism of these compounds typically yields carbon derivatives directly assimilable by a cell's metabolism. Another group of nitrogen compounds supports slower growth, is associated with excretion by cells of nonmetabolizable carbon compounds such as fusel oils, and is characterized by activation of the general control of amino acid biosynthesis (GAAC). Furthermore, NCR and GAAC appear interlinked, since expression of the GCN4 gene encoding the transcription factor that mediates GAAC is subject to NCR. We also observed that several transcriptional-regulation systems are active under a wider range of nitrogen supply conditions than anticipated. Other transcriptional-regulation systems acting on genes not involved in nitrogen metabolism, e.g., the pleiotropic-drug resistance and the unfolded-protein response systems, also respond to nitrogen. We have completed the lists of target genes of several nitrogen-sensitive regulons and have used sequence comparison tools to propose functions for about 20 orphan genes. Similar studies conducted for other nutrients should provide a more complete view of alternative metabolic pathways in yeast and contribute to the attribution of functions to many other orphan genes.
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