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Dufour E, Boulay J, Rincheval V, Sainsard-Chanet A. A causal link between respiration and senescence in Podospora anserina. Proc Natl Acad Sci U S A 2000; 97:4138-43. [PMID: 10759557 PMCID: PMC18174 DOI: 10.1073/pnas.070501997] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Senescence, a progressive degenerative process leading to age-related increase in mortality, is found in most eukaryotes. However, the molecular events underlying aging remain largely unknown. Understanding how longevity is regulated is a fundamental problem. Here we demonstrate that the respiratory function is a key factor that contributes to shortening lifespan of the filamentous fungus Podospora anserina. In this organism, senescence is systematically associated with mitochondrial DNA instabilities. We show that inactivation of the nuclear COX5 gene encoding subunit V of the cytochrome c oxidase complex leads to the exclusive use of the alternative respiratory pathway and to a decrease in production of reactive oxygen species. This inactivation results in a striking increase of longevity associated with stabilization of the mitochondrial chromosome. Moreover, accumulation of several senescence-specific mitochondrial DNA molecules is prevented in this nuclear mutant. These findings provide direct evidence of a causal link between mitochondrial metabolism and longevity in Podospora anserina.
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Affiliation(s)
- E Dufour
- Centre de Génétique Moléculaire-Centre National de la Recherche Scientifique, 91198 Gif sur Yvette Cedex, France
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2
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Luo Z, Freitag M, Sachs MS. Translational regulation in response to changes in amino acid availability in Neurospora crassa. Mol Cell Biol 1995; 15:5235-45. [PMID: 7565672 PMCID: PMC230771 DOI: 10.1128/mcb.15.10.5235] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We examined the regulation of Neurospora crassa arg-2 and cpc-1 in response to amino acid availability.arg-2 encodes the small subunit of arginine-specific carbamoyl phosphate synthetase; it is subject to unique negative regulation by Arg and is positively regulated in response to limitation for many different amino acids through a mechanism known as cross-pathway control. cpc-1 specifies a transcriptional activator important for crosspathway control. Expression of these genes was compared with that of the cytochrome oxidase subunit V gene, cox-5. Analyses of mRNA levels, polypeptide pulse-labeling results, and the distribution of mRNA in polysomes indicated that Arg-specific negative regulation of arg-2 affected the levels of both arg-2 mRNA and arg-2 mRNA translation. Negative translational effects on arg-2 and positive translational effects on cpc-1 were apparent soon after cells were provided with exogenous Arg. In cells limited for His, increased expression of arg-2 and cpc-1, and decreased expression of cox-5, also had translational and transcriptional components. The arg-2 and cpc-1 transcripts contain upstream open reading frames (uORFs), as do their Saccharomyces cerevisiae homologs CPA1 and GCN4. We examined the regulation of arg-2-lacZ reporter genes containing or lacking the uORF start codon; the capacity for arg-2 uORF translation appeared critical for controlling gene expression.
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Affiliation(s)
- Z Luo
- Department of Chemistry, Biochemistry, and Molecular Biology, Oregon Graduate Institute of Science and Technology, Portland, Oregon 97291-1000, USA
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Chow CM, RajBhandary UL. Developmental regulation of the gene for formate dehydrogenase in Neurospora crassa. J Bacteriol 1993; 175:3703-9. [PMID: 8509325 PMCID: PMC204785 DOI: 10.1128/jb.175.12.3703-3709.1993] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
We have isolated and characterized a gene, fdh, from Neurospora crassa which is developmentally regulated and which produces formate dehydrogenase activity when expressed in Escherichia coli. The gene is closely linked (less than 0.6 kb apart) to the leu-5 gene encoding mitochondrial leucyl-tRNA synthetase; the two genes are transcribed convergently from opposite strands. The expression patterns of these genes differ: fdh mRNA is found only during conidiation and early germination and is not detectable during mycelial growth, while leu-5 mRNA appears during germination and mycelial growth. The structure of the fdh gene was determined from the sequence of cDNA and genomic DNA clones and from mRNA mapping studies. The gene encodes a 375-amino-acid-long protein with sequence similarity to NAD-dependent dehydrogenases of the E. coli 3-phosphoglycerate dehydrogenase (serA gene product) subfamily. In particular, there is striking sequence similarity (52% identity) to formate dehydrogenase from Pseudomonas sp. strain 101. All of the residues thought to interact with NAD in the crystal structure of the Pseudomonas enzyme are conserved in the N. crassa enzyme. We have further shown that expression of the N. crassa gene in E. coli leads to the production of formate dehydrogenase activity, indicating that the N. crassa gene specifies a functional polypeptide.
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Affiliation(s)
- C M Chow
- Department of Biology, Massachusetts Institute of Technology, Cambridge 02139
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Characterization of the formate (for) locus, which encodes the cytosolic serine hydroxymethyltransferase of Neurospora crassa. Mol Cell Biol 1992. [PMID: 1532227 DOI: 10.1128/mcb.12.4.1412] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Serine hydroxymethyltransferase (SHMT) occupies a central position in one-carbon (C1) metabolism, catalyzing the reaction of serine and tetrahydrofolate to yield glycine and 5,10-methylenetetrahydrofolate. Methylenetetrahydrofolate serves as a donor of C1 units for the synthesis of numerous compounds, including purines, thymidylate, lipids, and methionine. We provide evidence that the formate (for) locus of Neurospora crassa encodes cytosolic SHMT. The for+ gene was localized to a 2.8-kb BglII fragment by complementation (restoration to formate-independent growth) of a strain carrying a recessive for allele, which confers a growth requirement for formate. The for+ gene encodes a polypeptide of 479 amino acids which shows significant similarity to amino acid sequences of SHMT from bacterial and mammalian sources (47 and 60% amino acid identity, respectively). The for+ mRNA has several different start and stop sites. The abundance of for+ mRNA increased in response to amino acid imbalance induced by glycine supplementation, suggesting regulation by the N. crassa cross-pathway control system, which is analogous to general amino acid control in Saccharomyces cerevisiae. This was confirmed by documenting that for+ expression increased in response to histidine limitation (induced by 3-amino-1,2,4-triazole) and that this response was dependent on the presence of a functional cross-pathway control-1 (cpc-1) gene, which encodes CPC1, a positively acting transcription factor. There are at least five potential CPC1 binding sites upstream of the for+ transcriptional start, as well as one that exactly matches the consensus CPC1 binding site in the first intron of the for+ gene.
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5
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McClung CR, Davis CR, Page KM, Denome SA. Characterization of the formate (for) locus, which encodes the cytosolic serine hydroxymethyltransferase of Neurospora crassa. Mol Cell Biol 1992; 12:1412-21. [PMID: 1532227 PMCID: PMC369582 DOI: 10.1128/mcb.12.4.1412-1421.1992] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Serine hydroxymethyltransferase (SHMT) occupies a central position in one-carbon (C1) metabolism, catalyzing the reaction of serine and tetrahydrofolate to yield glycine and 5,10-methylenetetrahydrofolate. Methylenetetrahydrofolate serves as a donor of C1 units for the synthesis of numerous compounds, including purines, thymidylate, lipids, and methionine. We provide evidence that the formate (for) locus of Neurospora crassa encodes cytosolic SHMT. The for+ gene was localized to a 2.8-kb BglII fragment by complementation (restoration to formate-independent growth) of a strain carrying a recessive for allele, which confers a growth requirement for formate. The for+ gene encodes a polypeptide of 479 amino acids which shows significant similarity to amino acid sequences of SHMT from bacterial and mammalian sources (47 and 60% amino acid identity, respectively). The for+ mRNA has several different start and stop sites. The abundance of for+ mRNA increased in response to amino acid imbalance induced by glycine supplementation, suggesting regulation by the N. crassa cross-pathway control system, which is analogous to general amino acid control in Saccharomyces cerevisiae. This was confirmed by documenting that for+ expression increased in response to histidine limitation (induced by 3-amino-1,2,4-triazole) and that this response was dependent on the presence of a functional cross-pathway control-1 (cpc-1) gene, which encodes CPC1, a positively acting transcription factor. There are at least five potential CPC1 binding sites upstream of the for+ transcriptional start, as well as one that exactly matches the consensus CPC1 binding site in the first intron of the for+ gene.
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Affiliation(s)
- C R McClung
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755
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6
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Removal of a hydrophobic domain within the mature portion of a mitochondrial inner membrane protein causes its mislocalization to the matrix. Mol Cell Biol 1990. [PMID: 2157966 DOI: 10.1128/mcb.10.5.1873] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have examined the import and intramitochondrial localization of the precursor to yeast cytochrome c oxidase subunit Va, a protein of the mitochondrial inner membrane. The results of studies on the import of subunit Va derivatives carrying altered presequences suggest that the uptake of this protein is highly efficient. We found that a presequence of only 5 amino acids (Met-Leu-Ser-Leu-Arg) could direct the import and localization of subunit Va with wild-type efficiency, as judged by several different assays. We also found that subunit Va could be effectively targeted to the mitochondrial inner membrane with a heterologous presequence that failed to direct import of its cognate protein. The results presented here confirmed those of an earlier study and showed clearly that the information required to "sort" subunit Va to the inner membrane resides in the mature protein sequence, not within the presequence per se. We present additional evidence that the aforementioned sorting information is contained, at least in part, in a hydrophobic stretch of 22 amino acids residing within the C-terminal third of the protein. Removal of this domain caused subunit Va to be mislocalized to the mitochondrial matrix.
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7
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Glaser SM, Miller BR, Cumsky MG. Removal of a hydrophobic domain within the mature portion of a mitochondrial inner membrane protein causes its mislocalization to the matrix. Mol Cell Biol 1990; 10:1873-81. [PMID: 2157966 PMCID: PMC360532 DOI: 10.1128/mcb.10.5.1873-1881.1990] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We have examined the import and intramitochondrial localization of the precursor to yeast cytochrome c oxidase subunit Va, a protein of the mitochondrial inner membrane. The results of studies on the import of subunit Va derivatives carrying altered presequences suggest that the uptake of this protein is highly efficient. We found that a presequence of only 5 amino acids (Met-Leu-Ser-Leu-Arg) could direct the import and localization of subunit Va with wild-type efficiency, as judged by several different assays. We also found that subunit Va could be effectively targeted to the mitochondrial inner membrane with a heterologous presequence that failed to direct import of its cognate protein. The results presented here confirmed those of an earlier study and showed clearly that the information required to "sort" subunit Va to the inner membrane resides in the mature protein sequence, not within the presequence per se. We present additional evidence that the aforementioned sorting information is contained, at least in part, in a hydrophobic stretch of 22 amino acids residing within the C-terminal third of the protein. Removal of this domain caused subunit Va to be mislocalized to the mitochondrial matrix.
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Affiliation(s)
- S M Glaser
- Department of Molecular Biology and Biochemistry, University of California, Irvine 92717
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Regulation of the nuclear genes encoding the cytoplasmic and mitochondrial leucyl-tRNA synthetases of Neurospora crassa. Mol Cell Biol 1990. [PMID: 2532300 DOI: 10.1128/mcb.9.11.4645] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We show that the nuclear genes for the cytoplasmic and mitochondrial leucyl-tRNA synthetase (LeuRS) of Neurospora crassa are distinct in their encoded proteins, codon usage, mRNA levels, and regulation. The 4.2-kilobase-pair region representing the structural gene for cytoplasmic LeuRS and flanking regions has been sequenced. The positions of the 5' and 3' ends of mRNA and of a single 62-base-pair intron have been mapped. The methionine-initiated open reading frame encoded a protein of 1,123 amino acids and displayed a strong codon bias. Although cytoplasmic LeuRS shares with mitochondrial LeuRS some general features common to most aminoacyl-tRNA synthetases, there is little amino acid sequence similarity between them, mRNA levels for cytoplasmic LeuRS were much higher than those for mitochondrial LeuRS. This observation and the strong codon bias in the cytoplasmic LeuRS gene may contribute to a greater abundance of cytoplasmic LeuRS than mitochondrial LeuRS. The genes for cytoplasmic and mitochondrial LeuRS are regulated independently. The cytoplasmic LeuRS gene is regulated by the cross-pathway control system in N. crassa, which is analogous to general amino acid control in Saccharomyces cerevisiae. The cytoplasmic LeuRS mRNA levels are induced by amino acid starvation resulting from the addition of aminotriazole. Part of this increase is due to utilization of new transcription start sites. In contrast, the mitochondrial LeuRS gene is not induced by amino acid limitation. However, the mitochondrial LeuRS mRNA levels did increase dramatically upon inhibition of mitochondrial protein synthesis by chloramphenicol or ethidium bromide or in the temperature-sensitive strain leu-5 carrying a mutation in the mitochondrial LeuRS structural gene.
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9
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Nuclear gene for mitochondrial leucyl-tRNA synthetase of Neurospora crassa: isolation, sequence, chromosomal mapping, and evidence that the leu-5 locus specifies structural information. Mol Cell Biol 1990. [PMID: 2574823 DOI: 10.1128/mcb.9.11.4631] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have isolated and characterized the nuclear gene for the mitochondrial leucyl-tRNA synthetase (LeuRS) of Neurospora crassa and have established that a defect in this structural gene is responsible for the leu-5 phenotype. We have purified mitochondrial LeuRS protein, determined its N-terminal sequence, and used this sequence information to identify and isolate a full-length genomic DNA clone. The 3.7-kilobase-pair region representing the structural gene and flanking regions has been sequenced. The 5' ends of the mRNA were mapped by S1 nuclease protection, and the 3' ends were determined from the sequence of cDNA clones. The gene contains a single short intron, 60 base pairs long. The methionine-initiated open reading frame specifies a 52-amino-acid mitochondrial targeting sequence followed by a 942-amino-acid protein. Restriction fragment length polymorphism analyses mapped the mitochondrial LeuRS structural gene to linkage group V, exactly where the leu-5 mutation had been mapped before. We show that the leu-5 strain has a defect in the structural gene for mitochondrial LeuRS by restoring growth under restrictive conditions for this strain after transformation with a wild-type copy of the mitochondrial LeuRS gene. We have cloned the mutant allele present in the leu-5 strain and identified the defect as being due to a Thr-to-Pro change in mitochondrial LeuRS. Finally, we have used immunoblotting to show that despite the apparent lack of mitochondrial LeuRS activity in leu-5 extracts, the leu-5 strain contains levels of mitochondrial LeuRS protein to similar to those of the wild-type strain.
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10
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Chow CM, Metzenberg RL, Rajbhandary UL. Nuclear gene for mitochondrial leucyl-tRNA synthetase of Neurospora crassa: isolation, sequence, chromosomal mapping, and evidence that the leu-5 locus specifies structural information. Mol Cell Biol 1989; 9:4631-44. [PMID: 2574823 PMCID: PMC363609 DOI: 10.1128/mcb.9.11.4631-4644.1989] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We have isolated and characterized the nuclear gene for the mitochondrial leucyl-tRNA synthetase (LeuRS) of Neurospora crassa and have established that a defect in this structural gene is responsible for the leu-5 phenotype. We have purified mitochondrial LeuRS protein, determined its N-terminal sequence, and used this sequence information to identify and isolate a full-length genomic DNA clone. The 3.7-kilobase-pair region representing the structural gene and flanking regions has been sequenced. The 5' ends of the mRNA were mapped by S1 nuclease protection, and the 3' ends were determined from the sequence of cDNA clones. The gene contains a single short intron, 60 base pairs long. The methionine-initiated open reading frame specifies a 52-amino-acid mitochondrial targeting sequence followed by a 942-amino-acid protein. Restriction fragment length polymorphism analyses mapped the mitochondrial LeuRS structural gene to linkage group V, exactly where the leu-5 mutation had been mapped before. We show that the leu-5 strain has a defect in the structural gene for mitochondrial LeuRS by restoring growth under restrictive conditions for this strain after transformation with a wild-type copy of the mitochondrial LeuRS gene. We have cloned the mutant allele present in the leu-5 strain and identified the defect as being due to a Thr-to-Pro change in mitochondrial LeuRS. Finally, we have used immunoblotting to show that despite the apparent lack of mitochondrial LeuRS activity in leu-5 extracts, the leu-5 strain contains levels of mitochondrial LeuRS protein to similar to those of the wild-type strain.
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Affiliation(s)
- C M Chow
- Department of Biology, Massachusetts Institute of Technology, Cambridge 02139
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11
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Chow CM, Rajbhandary UL. Regulation of the nuclear genes encoding the cytoplasmic and mitochondrial leucyl-tRNA synthetases of Neurospora crassa. Mol Cell Biol 1989; 9:4645-52. [PMID: 2532300 PMCID: PMC363610 DOI: 10.1128/mcb.9.11.4645-4652.1989] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We show that the nuclear genes for the cytoplasmic and mitochondrial leucyl-tRNA synthetase (LeuRS) of Neurospora crassa are distinct in their encoded proteins, codon usage, mRNA levels, and regulation. The 4.2-kilobase-pair region representing the structural gene for cytoplasmic LeuRS and flanking regions has been sequenced. The positions of the 5' and 3' ends of mRNA and of a single 62-base-pair intron have been mapped. The methionine-initiated open reading frame encoded a protein of 1,123 amino acids and displayed a strong codon bias. Although cytoplasmic LeuRS shares with mitochondrial LeuRS some general features common to most aminoacyl-tRNA synthetases, there is little amino acid sequence similarity between them, mRNA levels for cytoplasmic LeuRS were much higher than those for mitochondrial LeuRS. This observation and the strong codon bias in the cytoplasmic LeuRS gene may contribute to a greater abundance of cytoplasmic LeuRS than mitochondrial LeuRS. The genes for cytoplasmic and mitochondrial LeuRS are regulated independently. The cytoplasmic LeuRS gene is regulated by the cross-pathway control system in N. crassa, which is analogous to general amino acid control in Saccharomyces cerevisiae. The cytoplasmic LeuRS mRNA levels are induced by amino acid starvation resulting from the addition of aminotriazole. Part of this increase is due to utilization of new transcription start sites. In contrast, the mitochondrial LeuRS gene is not induced by amino acid limitation. However, the mitochondrial LeuRS mRNA levels did increase dramatically upon inhibition of mitochondrial protein synthesis by chloramphenicol or ethidium bromide or in the temperature-sensitive strain leu-5 carrying a mutation in the mitochondrial LeuRS structural gene.
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Affiliation(s)
- C M Chow
- Department of Biology, Massachusetts Institute of Technology, Cambridge 02139
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