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Shaw AE, Mihelich MN, Whitted JE, Reitman HJ, Timmerman AJ, Tehseen M, Hamdan SM, Schauer GD. Revised mechanism of hydroxyurea-induced cell cycle arrest and an improved alternative. Proc Natl Acad Sci U S A 2024; 121:e2404470121. [PMID: 39374399 DOI: 10.1073/pnas.2404470121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2024] [Accepted: 09/04/2024] [Indexed: 10/09/2024] Open
Abstract
Replication stress describes endogenous and exogenous challenges to DNA replication in the S-phase. Stress during this critical process causes helicase-polymerase decoupling at replication forks, triggering the S-phase checkpoint, which orchestrates global replication fork stalling and delayed entry into G2. The replication stressor most often used to induce the checkpoint response in yeast is hydroxyurea (HU), a clinically used chemotherapeutic. The primary mechanism of S-phase checkpoint activation by HU has thus far been considered to be a reduction of deoxynucleotide triphosphate synthesis by inhibition of ribonucleotide reductase (RNR), leading to helicase-polymerase decoupling and subsequent activation of the checkpoint, facilitated by the replisome-associated mediator Mrc1. In contrast, we observe that HU causes cell cycle arrest in budding yeast independent of both the Mrc1-mediated replication checkpoint response and the Psk1-Mrc1 oxidative signaling pathway. We demonstrate a direct relationship between HU incubation and reactive oxygen species (ROS) production in yeast and human cells and show that antioxidants restore growth of yeast in HU. We further observe that ROS strongly inhibits the in vitro polymerase activity of replicative polymerases (Pols), Pol α, Pol δ, and Pol ε, causing polymerase complex dissociation and subsequent loss of DNA substrate binding, likely through oxidation of their integral iron-sulfur (Fe-S) clusters. Finally, we present "RNR-deg," a genetically engineered alternative to HU in yeast with greatly increased specificity of RNR inhibition, allowing researchers to achieve fast, nontoxic, and more readily reversible checkpoint activation compared to HU, avoiding harmful ROS generation and associated downstream cellular effects that may confound interpretation of results.
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Affiliation(s)
- Alisa E Shaw
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80525
| | - Mattias N Mihelich
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80525
| | - Jackson E Whitted
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80525
| | - Hannah J Reitman
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80525
| | - Adam J Timmerman
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80525
| | - Muhammad Tehseen
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia
| | - Samir M Hamdan
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia
| | - Grant D Schauer
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80525
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Elevated Levels of the Escherichia coli nrdAB-Encoded Ribonucleotide Reductase Counteract the Toxicity Caused by an Increased Abundance of the β Clamp. J Bacteriol 2021; 203:e0030421. [PMID: 34543109 DOI: 10.1128/jb.00304-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Expression of the Escherichia coli dnaN-encoded β clamp at ≥10-fold higher than chromosomally expressed levels impedes growth by interfering with DNA replication. A mutant clamp (βE202K bearing a glutamic acid-to-lysine substitution at residue 202) binds to DNA polymerase III (Pol III) with higher affinity than the wild-type clamp, suggesting that its failure to impede growth is independent of its ability to sequester Pol III away from the replication fork. Our results demonstrate that the dnaNE202K strain underinitiates DNA replication due to insufficient levels of DnaA-ATP and expresses several DnaA-regulated genes at altered levels, including nrdAB, that encode the class 1a ribonucleotide reductase (RNR). Elevated expression of nrdAB was dependent on hda function. As the β clamp-Hda complex regulates the activity of DnaA by stimulating its intrinsic ATPase activity, this finding suggests that the dnaNE202K allele supports an elevated level of Hda activity in vivo compared with the wild-type strain. In contrast, using an in vitro assay reconstituted with purified components the βE202K and wild-type clamp proteins supported comparable levels of Hda activity. Nevertheless, co-overexpression of the nrdAB-encoded RNR relieved the growth defect caused by elevated levels of the β clamp. These results support a model in which increased cellular levels of DNA precursors relieve the ability of elevated β clamp levels to impede growth and suggest either that multiple effects stemming from the dnaNE202K mutation contribute to elevated nrdAB levels or that Hda plays a noncatalytic role in regulating DnaA-ATP by sequestering it to reduce its availability. IMPORTANCE DnaA bound to ATP acts in initiation of DNA replication and regulates the expression of several genes whose products act in DNA metabolism. The state of the ATP bound to DnaA is regulated in part by the β clamp-Hda complex. The dnaNE202K allele was identified by virtue of its inability to impede growth when expressed ≥10-fold higher than chromosomally expressed levels. While the dnaNE202K strain exhibits several phenotypes consistent with heightened Hda activity, the wild-type and βE202K clamp proteins support equivalent levels of Hda activity in vitro. Taken together, these results suggest that βE202K-Hda plays a noncatalytic role in regulating DnaA-ATP. This, as well as alternative models, is discussed.
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Babu VMP, Itsko M, Baxter JC, Schaaper RM, Sutton MD. Insufficient levels of the nrdAB-encoded ribonucleotide reductase underlie the severe growth defect of the Δhda E. coli strain. Mol Microbiol 2017; 104:377-399. [PMID: 28130843 DOI: 10.1111/mmi.13632] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/23/2017] [Indexed: 11/28/2022]
Abstract
The ATP-bound form of the Escherichia coli DnaA replication initiator protein remodels the chromosomal origin of replication, oriC, to load the replicative helicase. The primary mechanism for regulating the activity of DnaA involves the Hda and β clamp proteins, which act together to dramatically stimulate the intrinsic DNA-dependent ATPase activity of DnaA via a process termed Regulatory Inactivation of DnaA. In addition to hyperinitiation, strains lacking hda function also exhibit cold sensitive growth at 30°C. Strains impaired for the other regulators of initiation (i.e., ΔseqA or ΔdatA) fail to exhibit cold sensitivity. The goal of this study was to gain insight into why loss of hda function impedes growth. We used a genetic approach to isolate 9 suppressors of Δhda cold sensitivity, and characterized the mechanistic basis by which these suppressors alleviated Δhda cold sensitivity. Taken together, our results provide strong support for the view that the fundamental defect associated with Δhda is diminished levels of DNA precursors, particularly dGTP and dATP. We discuss possible mechanisms by which the suppressors identified here may regulate dNTP pool size, as well as similarities in phenotypes between the Δhda strain and hda+ strains exposed to the ribonucleotide reductase inhibitor hydroxyurea.
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Affiliation(s)
- Vignesh M P Babu
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, NY, USA
| | - Mark Itsko
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Jamie C Baxter
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, NY, USA
| | - Roel M Schaaper
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Mark D Sutton
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, NY, USA
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Vrček IV, Šakić D, Vrček V, Zipse H, Biruš M. Computational study of radicals derived from hydroxyurea and its methylated analogues. Org Biomol Chem 2012; 10:1196-206. [DOI: 10.1039/c1ob06594g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Davies BW, Kohanski MA, Simmons LA, Winkler JA, Collins JJ, Walker GC. Hydroxyurea induces hydroxyl radical-mediated cell death in Escherichia coli. Mol Cell 2010; 36:845-60. [PMID: 20005847 DOI: 10.1016/j.molcel.2009.11.024] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2009] [Revised: 07/13/2009] [Accepted: 08/13/2009] [Indexed: 01/18/2023]
Abstract
Hydroxyurea (HU) specifically inhibits class I ribonucleotide reductase (RNR), depleting dNTP pools and leading to replication fork arrest. Although HU inhibition of RNR is well recognized, the mechanism by which it leads to cell death remains unknown. To investigate the mechanism of HU-induced cell death, we used a systems-level approach to determine the genomic and physiological responses of E. coli to HU treatment. Our results suggest a model by which HU treatment rapidly induces a set of protective responses to manage genomic instability. Continued HU stress activates iron uptake and toxins MazF and RelE, whose activity causes the synthesis of incompletely translated proteins and stimulation of envelope stress responses. These effects alter the properties of one of the cell's terminal cytochrome oxidases, causing an increase in superoxide production. The increased superoxide production, together with the increased iron uptake, fuels the formation of hydroxyl radicals that contribute to HU-induced cell death.
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Affiliation(s)
- Bryan W Davies
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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Abstract
All organisms possess a diverse set of genetic programs that are used to alter cellular physiology in response to environmental cues. The gram-negative bacterium, Escherichia coli, mounts what is known as the "SOS response" following DNA damage, replication fork arrest, and a myriad of other environmental stresses. For over 50 years, E. coli has served as the paradigm for our understanding of the transcriptional, and physiological changes that occur following DNA damage (400). In this chapter, we summarize the current view of the SOS response and discuss how this genetic circuit is regulated. In addition to examining the E. coli SOS response, we also include a discussion of the SOS regulatory networks in other bacteria to provide a broader perspective on how prokaryotes respond to DNA damage.
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The ribonucleotide reductases — A unique group of metalloenzymes essential for cell proliferation. STRUCTURE AND BONDING 2007. [DOI: 10.1007/bfb0111318] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Krogan NJ, Zaharik ML, Neuhard J, Kelln RA. A combination of three mutations, dcd, pyrH, and cdd, establishes thymidine (Deoxyuridine) auxotrophy in thyA+ strains of Salmonella typhimurium. J Bacteriol 1998; 180:5891-5. [PMID: 9811646 PMCID: PMC107662 DOI: 10.1128/jb.180.22.5891-5895.1998] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The dum gene of Salmonella typhimurium was originally identified as a gene involved in dUMP synthesis (C. F. Beck et al., J. Bacteriol. 129:305-316, 1977). In the genetic background used in their selection, the joint acquisition of a dcd (dCTP deaminase) and a dum mutation established a condition of thymidine (deoxyuridine) auxotrophy. In this study, we show that dum is identical to pyrH, the gene encoding UMP kinase. The level of UMP kinase activity in the dum mutant was found to be only 30% of that observed for the dum+ strain. Thymidine prototrophy was restored to the original dum dcd mutant (KP1361) either by transduction using a pyrH+ donor or by complementation with either of two pyrH+-carrying plasmids. Thymidine auxotrophy could be reconstructed in the dum+ derivative (KP1389) by the introduction of a mutant pyrH allele. To define the minimal mutational complement necessary to produce thymidine auxotrophy in thyA+ strains, a dcd::Km null mutation was constructed. In the wild-type background, dcd::Km alone or in combination with a pyrH (dum) mutation did not result in a thymidine requirement. A third mutation, cdd (cytidine-deoxycytidine deaminase), was required together with the dcd and pyrH mutations to impart thymidine auxotrophy.
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Affiliation(s)
- N J Krogan
- Department of Chemistry, University of Regina, Regina, Saskatchewan, Canada
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Larsson A, Climent I, Nordlund P, Sahlin M, Sjöberg BM. Structural and functional characterization of two mutated R2 proteins of Escherichia coli ribonucleotide reductase. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 237:58-63. [PMID: 8620893 DOI: 10.1111/j.1432-1033.1996.0058n.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The R2 protein of ribonucleotide reductase from Escherichia coli is a homodimeric tyrosyl-radical-containing enzyme with two identical dinuclear iron centers. Two randomly generated genomic mutants, nrdB-1 and nrdB-2, that produce R2 enzymes with low enzymatic activity, have been cloned and characterized to identify functionally important residues and areas of the enzyme. The mutations were identified as Pro348 to leucine in nrdB-1 and Leu304 to phenylalanine in nrdB-2. Both mutations are the results of single amino acid replacements of non-conserved residues. The three-dimensional structures of [L348]R2 and [F304]R2 have been determined to 0.26-nm and 0.28-nm resolution, respectively. Compared with wild-type R2, [L348]R2 binds with higher affinity to R1, probably due to increased flexibility of its C-terminus. Since the three-dimensional structure, iron-center properties and radical properties of [L348]R2 are comparable to those of wild-type R2, the low catalytic activity of the holoenzyme is probably caused by a perturbed interaction between R2 and R1. The [F304]R2 enzyme has increased radical sensitivity and low catalytic activity compared with wild-type R2. In [F304]R2 the only significant change in structure is that the evolutionary conserved Ser211 forms a different hydrogen bond to a distorted helix. The results obtained with [F304]R2 indicate that structural changes in E. coli R2 in the vicinity of this helix distortion can influence the catalytic activity of the holoenzyme.
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Affiliation(s)
- A Larsson
- Department of Molecular Biology, University of Stockholm, Sweden
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10
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Sjöberg BM. Structure of Ribonucleotide Reductase from Escherichia coli. NUCLEIC ACIDS AND MOLECULAR BIOLOGY 1995. [DOI: 10.1007/978-3-642-79488-9_10] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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11
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Jordan A, Gibert I, Barbé J. Cloning and sequencing of the genes from Salmonella typhimurium encoding a new bacterial ribonucleotide reductase. J Bacteriol 1994; 176:3420-7. [PMID: 8195103 PMCID: PMC205520 DOI: 10.1128/jb.176.11.3420-3427.1994] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
A plasmid library of Salmonella typhimurium was used to complement a temperature-sensitive nrdA mutant of Escherichia coli. Complementation was obtained with two different classes of plasmids, one carrying the E. coli nrdAB-like genes and the second containing an operon encoding a new bacterial ribonucleotide reductase. Plasmids harboring these new reductase genes also enable obligately anaerobic nrdB::Mud1 E. coli mutants to grow in the presence of oxygen. This operon consists of two open reading frames, which have been designated nrdE (2,145 bp) and nrdF (969 bp). The deduced amino acid sequences of the nrdE and nrdF products include the catalytically important residues conserved in ribonucleotide reductase enzymes of class I and show 25 and 28% overall identity with the R1 and R2 protein, respectively, of the aerobic ribonucleoside diphosphate reductase of E. coli. The 3' end of the sequenced 4.9-kb fragment corresponds to the upstream region of the previously published proU operon of both S. typhimurium and E. coli, indicating that the nrdEF genes are at 57 min on the chromosomal maps of these two bacterial species. Analysis of the nrdEF and proU sequences demonstrates that transcription of the nrdEF genes is in the clockwise direction on the S. typhimurium and E. coli maps.
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Affiliation(s)
- A Jordan
- Department of Genetics and Microbiology, Faculty of Sciences, Autonomous University of Barcelona, Bellatera, Spain
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12
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Russel M, Model P, Holmgren A. Thioredoxin or glutaredoxin in Escherichia coli is essential for sulfate reduction but not for deoxyribonucleotide synthesis. J Bacteriol 1990; 172:1923-9. [PMID: 2180911 PMCID: PMC208687 DOI: 10.1128/jb.172.4.1923-1929.1990] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We have shown previously that Escherichia coli cells constructed to lack both thioredoxin and glutaredoxin are not viable unless they also acquire an additional mutation, which we called X. Here we show that X is a cysA mutation. Our data suggest that the inviability of a trxA grx double mutant is due to the accumulation of 3'-phosphoadenosine 5'-phosphosulfate (PAPS), an intermediate in the sulfate assimilation pathway. The presence of excess cystine at a concentration sufficient to repress the sulfate assimilation pathway obviates the need for an X mutation and prevents the lethality of a novel cys+ trxA grx double mutant designated strain A522. Mutations in genes required for PAPS synthesis (cysA or cysC) protect cells from the otherwise lethal effect of elimination of both thioredoxin and glutaredoxin even in the absence of excess cystine. Both thioredoxin and glutaredoxin have been shown to be hydrogen donors for PAPS reductase (cysH) in vitro (M. L.-S. Tsang, J. Bacteriol. 146:1059-1066, 1981), and one or the other of these compounds is presumably essential in vivo for growth on minimal medium containing sulfate as the sulfur source. The cells which lack both thioredoxin and glutaredoxin require cystine or glutathione for growth on minimal medium but maintain an active ribonucleotide reduction system. Thus, E. coli must contain a third hydrogen donor active with ribonucleotide reductase.
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Affiliation(s)
- M Russel
- Laboratory of Genetics, Rockefeller University, New York, New York 10021
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Russel M, Holmgren A. Construction and characterization of glutaredoxin-negative mutants of Escherichia coli. Proc Natl Acad Sci U S A 1988; 85:990-4. [PMID: 3277191 PMCID: PMC279686 DOI: 10.1073/pnas.85.4.990] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Deoxyribonucleotides, the precursors of DNA, are formed de novo by ribonucleotide reductase, and in vitro thioredoxin or glutathione plus glutaredoxin have been isolated as hydrogen donors. The in vivo hydrogen donor for ribonucleotide reductase is not known. To study this, the Escherichia coli glutaredoxin gene (255 base pairs) was inactivated by inserting a 2-kilobase kanamycin-resistance fragment into the coding sequence of the cloned gene. The inactivated gene was inserted into the E. coli chromosome and mapped to about 18.5 min. A gene replacement technique was used to obtain a strain, A407, that lacked glutaredoxin by radioimmunoassay and by enzymatic assay with ribonucleotide reductase. Glutaredoxin was found not to be essential for viability of E. coli. Thioredoxin is also not essential for viability, as had been shown earlier, but a double mutant lacking glutaredoxin and thioredoxin could not be obtained by P1 transduction on a defined medium, indicating that either thioredoxin or glutaredoxin is essential. In rich medium, very slowly growing, unstable transductants were obtained that at high frequency gave rise to better growing cells. One such isolate, A410, was shown to still lack glutaredoxin and thioredoxin.
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Affiliation(s)
- M Russel
- Laboratory of Genetics, Rockefeller University, New York, NY 10021
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14
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Süss F, Frunder B, Klaus S, Noack D. Characterization of a thermosensitive mutant of Streptomyces hygroscopicus defective in both DNA and RNA syntheses. J Basic Microbiol 1988; 28:541-51. [PMID: 2466979 DOI: 10.1002/jobm.3620280816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A stable temperature sensitive mutant of Streptomyces hygroscopicus JA6599 defective in both DNA and RNA syntheses is described. The mutant ts35 is characterized by an immediate stop of DNA synthesis and continued protein synthesis after transfer to restrictive temperature. The reinitiation of DNA synthesis begins immediately after a return to the permissive temperature. This kinetics of macromolecular synthesis at restrictive temperature appears to share similarities with a defect in the DNA elongation process, as described for Escherichia coli (Carl 1970, Hanna and Carl 1975). The simultaneous stop of both DNA and RNA syntheses may be caused by an additional mutational event affecting also the RNA synthesis. The data were discussed with respect to similar results in E. coli.
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Affiliation(s)
- F Süss
- Akademie der Wissenschaften der DDR
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15
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Kren B, Parsell D, Fuchs JA. Isolation and characterization of an Escherichia coli K-12 mutant deficient in glutaredoxin. J Bacteriol 1988; 170:308-15. [PMID: 3275617 PMCID: PMC210643 DOI: 10.1128/jb.170.1.308-315.1988] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Mutants of Escherichia coli K-12 deficient in glutaredoxin were isolated and partially characterized. The mutants have detectable but significantly reduced glutaredoxin activity in assays of whole cells made permeable with ether as well as in assays of crude extracts coupled to ribonucleotide reductase. In vivo, the mutants appear to be deficient in both sulfate and ribonucleotide reduction, suggesting that in vivo glutaredoxin is the preferred cofactor for ribonucleotide reductase and adenosine 3'-phosphate 5'-phosphosulfate reductase. Complementation of the mutant phenotype by transformants was used to clone the wild-type glutaredoxin allele. The transformants had a high level of glutaredoxin activity and contained a plasmid with an insert that had a restriction endonuclease pattern identical to that predicted by the DNA sequence for glutaredoxin determined by Hoog et al. (J.-O. Hoog, H. von Bahr-Lindstrom, H. Jornvall, and A. Holmgren, Gene 43:13-21, 1986).
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Affiliation(s)
- B Kren
- Department of Biochemistry, University of Minnesota, St. Paul 55108
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Taschner PE, Verest JG, Woldringh CL. Genetic and morphological characterization of ftsB and nrdB mutants of Escherichia coli. J Bacteriol 1987; 169:19-25. [PMID: 3098730 PMCID: PMC211728 DOI: 10.1128/jb.169.1.19-25.1987] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The ftsB gene of Escherichia coli is believed to be involved in cell division. In this report, we show that plasmids containing the nrdB gene could complement the ftsB mutation, suggesting that ftsB is an allele of nrdB. We compared changes in the cell shape of isogenic nrdA, nrdB, ftsB, and pbpB strains at permissive and restrictive temperatures. Although in rich medium all strains produced filaments at the restrictive temperature, in minimal medium only a 50 to 100% increase in mean cell mass occurred in the nrdA, nrdB, and ftsB strains. The typical pbpB cell division mutant also formed long filaments at low growth rates. Visualization of nucleoid structure by fluorescence microscopy demonstrated that nucleoid segregation was affected by nrdA, nrdB, and ftsB mutations at the restrictive temperature. Measurements of beta-galactosidase activity in lambda p(sfiA::lac) lysogenic nrdA, nrdB, and ftsB mutants in rich medium at the restrictive temperature showed that filamentation in the nrdA mutant was caused by sfiA (sulA) induction, while filamentation in nrdB and ftsB mutants was sfiA independent, suggesting an SOS-independent inhibition of cell division.
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17
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Kren B, Fuchs JA. Characterization of the ftsB gene as an allele of the nrdB gene in Escherichia coli. J Bacteriol 1987; 169:14-8. [PMID: 3025167 PMCID: PMC211727 DOI: 10.1128/jb.169.1.14-18.1987] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
A temperature-sensitive, salt-rescuable ftsB cell division mutant, MFT84, was found to be hydroxyurea sensitive on low-salt medium. Complementation studies with plasmids and a marker rescue study with bacteriophage M13 nrd indicated that ftsB is an allele of nrdB and that the mutation occurs in the region corresponding to nucleotides 6729 to 7032 of the nrdB gene. Enzymatic characterization demonstrated that the B2 subunit of ribonucleoside-diphosphate reductase encoded by ftsB was responsible for the decreased activity and the thermolability of the enzyme. The ftsB-encoded B2 subunit was activated by the addition of 0.1 M NaCl to an in vitro assay, corroborating the in vivo temperature-dependent salt requirement was a result of a defective B2 subunit.
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Platz A, Sjöberg BM. Mutationally altered ribonucleotide reductase from Escherichia coli: characterization of mutations isolated on multicopy plasmids. J Bacteriol 1984; 160:1010-6. [PMID: 6389503 PMCID: PMC215810 DOI: 10.1128/jb.160.3.1010-1016.1984] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The Escherichia coli ribonucleotide reductase genes (nrd genes) were mutagenized at random. Point mutations were introduced in vitro into a recombinant nrd plasmid. Transformants were initially screened for altered tolerance toward the drug hydroxyurea and further characterized by enzymatic and immunological methods. The screening procedure could pick out defects in either of the two subunits of ribonucleotide reductase. Cells carrying the nrd plasmid pPS2 were earlier shown to have levels of ribonucleotide reductase molecules that were 10 to 20 times higher than those in wild-type cells. We now demonstrate that the enzymatic activity in gently lysed pPS2-containing cells on cellophane disks is six times higher than in wild-type cells. Supplementation of the pPS2-containing lysates with a purified thioredoxin system results in a further 4.5-fold stimulation of the enzymatic activity, which implies a functional shortage of the electron donor system(s) for ribonucleotide reduction in pPS2-containing cells.
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Keil RL, Chaleff RS. Genetic characterization of hydroxyurea-resistant mutants obtained from cell cultures of Nicotiana tabacum. ACTA ACUST UNITED AC 1983. [DOI: 10.1007/bf00327669] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Yamada M, Takeda Y, Okamoto K, Hirota Y. Physical map of the nrdA-nrdB-ftsB-glpT region of the chromosomal DNA of Escherichia coli. Gene 1982; 18:309-18. [PMID: 6290334 DOI: 10.1016/0378-1119(82)90169-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Seven pLC plasmids (pLC 3-46, 8-12, 8-24, 8-29, 14-12, 19-24 and 42-17) which complemented nrdA, nrdB, ftsB and/or glpT mutations of Escherichia coli were analyzed. A restriction map of each plasmid was constructed and restriction fragments were subcloned into pBR322. A physical map of approx. a 15 X 10(6) Mr segment of the chromosomal DNA was deduced from the overlapping region of the pLC plasmids. The pLC plasmids and newly constructed plasmids were examined for the ability to rescue the mutations. The complementation tests defined the location of the genes in the 15 X 10(6) Mr segment in the following order: nrdA-nrdB-ftsB-glpT. Functional nrdAB and ftsB genes were located in the 3.1 X 10(6) Mr EcoRI-PstI fragment.
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Ribonucleoside diphosphate reductase from Escherichia coli. An immunological assay and a novel purification from an overproducing strain lysogenic for phage lambdadnrd. J Biol Chem 1977. [DOI: 10.1016/s0021-9258(17)40040-8] [Citation(s) in RCA: 65] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Beck CF, Neuhard J, Thomassen E. Thymidine-requiring mutants of Salmonella typhimurium that are defective in deoxyuridine 5'-phosphate synthesis. J Bacteriol 1977; 129:305-16. [PMID: 318643 PMCID: PMC234928 DOI: 10.1128/jb.129.1.305-316.1977] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
In a Salmonella typhimurium strain made diploid for the thy region by introduction of the Escherichia coli episome, F'15, mutants resistant to trimethoprim in the presence of thymidine were selected. One was shown to be defective in deoxyuridine 5'-phosphate (dUMP) synthesis; it requires deoxyuridine or thymidine for growth and is sensitive to trimethoprim in the presence of deoxyuridine. Genetic studies showed that the mutant is mutated in two genes, dcd and dum, located at 70 and 18 min, respectively, on the Salmonella linkage map. The dcd gene cotransduces 95% with udk, the structural gene for uridine kinase. Both mutations are necessary to create a deoxyuridine requirement, providing evidence for the existence of two independent pathways for dUMP synthesis. Pool studies showed that a dum mutation by itself causes a small decrease in the deoxythymidine 5'-triphosphate (dTTP) pool of the cells, whereas a dcd mutation results in a much more marked decrease. The double mutant dcd dum, when incubated in the absence of deoxyuridine, contains barely detectable levels of dTTP. Enzyme analysis revealed that dcd encodes deoxycytidine 5'-triphosphate deaminase. The gene product of the dum gene has not yet been identified; it does not encode either subunit of ribonucleoside diphosphate reductase or deoxyuridine 5'-triphosphate pyrophosphatase. Mutants deleted for the dcd-udk region of the S. typhimurium chromosome were isolated.
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Abstract
The structural genes coding for the B1 and B2 subunits of the enzyme ribonucleoside diphosphate reductase, nrdA (formerly designated dnaF) and nrdB, respectively, have been mapped in Escherichia coli. They are located at approximately 48 min. The gene order in this region of the E. coli chromosome was found to be purF glpT nrdB nrdA nalA cdd dcd his.
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Abstract
A resume has been presented of some recent investigations which show that DNA synthesis can be initiated in many types of quiescent animal cells by external stimuli, by introducing a quiescent nucleus into the cytoplasm of a proliferating cell, or by a virus infection. The components of the DNA replication apparatus are described. It is shown that deoxyribonucleoside triphosphate pools increase substantially in animal cells at the time DNA synthesis is initiated due to the enhanced activities of enzymes functioning in nucleotide synthesis. Especially striking is the increase of thymidine kinase activity, indicating that this enzyme may be a useful marker of the shift from the quiescent to the replicative state. The thymidine kinase isozymes of vertebrate cells have been characterized. Thymidine kinase F, which is found principally in the cytosol, is the isozyme that increases when G1 (Go) phase cells are stimulated or infected with oncogenic viruses. Chick cytosol thymidine kinase F can also be reactivated by introducing differentiated chick erythrocyte nuclei into the cytoplasm of enzyme-deficient LM (TK-) mouse cells. Furthermore, herpesviruses code for distinctive, virus-specific thymidine kinase isozymes, so that another way to transform thymidine kinase-deficient LM TK-) cells to kinase-positive cells is by infecting them with UV-irradiated herpes simplex viruses. The experiments on the activation of DNA synthesis and thymidine kinase F activity have been discussed in the context of the proliferative activity in vivo and the immortalization in culture of neoplastic cells. These experiments suggest that genes determining cell cycle proteins are readily accessible to transcription and translation in essentially all nucleated cells. The tendency of transformed cells to become multinucleated after cytochaliasin B treatment also suggests that one important difference between malignant cells and most normal cells may be the ability of malignant cells to 'stockpile' the proteins (and/or their messenger RNAs) of the DNA replicative apparatus and to maintain the 'stockpiles' in progeny cells.
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Johnson JR, Collins GM, Rementer ML, Hall DH. Novel mechanism of resistance to folate analogues: ribonucleoside diphosphate reductase deficiency in bacteriophage T4. Antimicrob Agents Chemother 1976; 9:292-300. [PMID: 1267427 PMCID: PMC429517 DOI: 10.1128/aac.9.2.292] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Some spontaneously occurring bacteriophage T4 mutants (far mutants) were able to form plaques in the presence of concentrations of folate analogues that completely inhibit plaque formation by wild-type phage T4. Some of these far mutants were shown to be ribonucleoside diphosphate (RDP) reductase (EC 1.17.4.1) deficient, and some independently isolated RDP reductase-deficient mutants (nrd mutants) were shown to be folate analogue resistant. The map positions of the RDP reductase-deficient far mutants were shown to be within the genes controlling the phage-induced RDP reductase activity.
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27
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Abstract
A mutant of Escherichia coli that contains essentially no detectable glutathione has been isolated. The mutant contains a very low level of the enzyme glutathione synthetase and accumulates lambda-glutamyl cysteine at a concentration approximately equal to the level of glutathione found in its parent. No significant differences in growth were observed between the mutant and its parent. However, the activity of at least one enzyme was found to be affected by the absence of glutathione; the specific activity of the B1 subunit of ribonucleoside diphosphate reductase was greatly reduced. The possibility that the decreased B1 activity is due to a mutation in the structural gene coding for B1 or its regulatory gene could be eliminated. This suggests that one role of glutathione in the cell is to maintain at least this one protein in an active state. We propose the designation gshB for the gene coding for glutathione synthetase.
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Follmann H. Die enzymatische Ribonucleotid-Reduktion: Biosyntheseweg der Desoxyribonucleotide. Angew Chem Int Ed Engl 1974. [DOI: 10.1002/ange.19740861704] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Follmann H. Enzymatic reduction of ribonucleotides: biosynthesis pathway of deoxyribonucleotides. Angew Chem Int Ed Engl 1974; 13:569-79. [PMID: 4214088 DOI: 10.1002/anie.197405691] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Karlstrom HO, Fuchs JA. A Mutant of Escherichia coli Defective in Ribonucleosidediphosphate Reductase. 2. Characterization of the Enzymatic Defect. ACTA ACUST UNITED AC 1973. [DOI: 10.1111/j.1432-1033.1973.tb02628.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Fuchs JA, Neuhard J. A mutant of Escherichia coli defective in ribonucleosidediphosphate reductase. 1. Isolation of the mutant as a deoxyuridine auxotroph. EUROPEAN JOURNAL OF BIOCHEMISTRY 1973; 32:451-6. [PMID: 4571065 DOI: 10.1111/j.1432-1033.1973.tb02627.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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