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Yang KB, Cameranesi M, Gowder M, Martinez C, Shamovsky Y, Epshtein V, Hao Z, Nguyen T, Nirenstein E, Shamovsky I, Rasouly A, Nudler E. High-resolution landscape of an antibiotic binding site. Nature 2023; 622:180-187. [PMID: 37648864 PMCID: PMC10550828 DOI: 10.1038/s41586-023-06495-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 07/28/2023] [Indexed: 09/01/2023]
Abstract
Antibiotic binding sites are located in important domains of essential enzymes and have been extensively studied in the context of resistance mutations; however, their study is limited by positive selection. Using multiplex genome engineering1 to overcome this constraint, we generate and characterize a collection of 760 single-residue mutants encompassing the entire rifampicin binding site of Escherichia coli RNA polymerase (RNAP). By genetically mapping drug-enzyme interactions, we identify an alpha helix where mutations considerably enhance or disrupt rifampicin binding. We find mutations in this region that prolong antibiotic binding, converting rifampicin from a bacteriostatic to bactericidal drug by inducing lethal DNA breaks. The latter are replication dependent, indicating that rifampicin kills by causing detrimental transcription-replication conflicts at promoters. We also identify additional binding site mutations that greatly increase the speed of RNAP.Fast RNAP depletes the cell of nucleotides, alters cell sensitivity to different antibiotics and provides a cold growth advantage. Finally, by mapping natural rpoB sequence diversity, we discover that functional rifampicin binding site mutations that alter RNAP properties or confer drug resistance occur frequently in nature.
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Affiliation(s)
- Kevin B Yang
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Maria Cameranesi
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Manjunath Gowder
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Criseyda Martinez
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Yosef Shamovsky
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Vitaliy Epshtein
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Zhitai Hao
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Thao Nguyen
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Eric Nirenstein
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Ilya Shamovsky
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA
| | - Aviram Rasouly
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA.
- Howard Hughes Medical Institute, New York University School of Medicine, New York, NY, USA.
| | - Evgeny Nudler
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY, USA.
- Howard Hughes Medical Institute, New York University School of Medicine, New York, NY, USA.
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Zhang H, Gogada R, Yadav N, Lella RK, Badeaux M, Ayres M, Gandhi V, Tang DG, Chandra D. Defective molecular timer in the absence of nucleotides leads to inefficient caspase activation. PLoS One 2011; 6:e16379. [PMID: 21297999 PMCID: PMC3029307 DOI: 10.1371/journal.pone.0016379] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2010] [Accepted: 12/13/2010] [Indexed: 01/26/2023] Open
Abstract
In the intrinsic death pathway, cytochrome C (CC) released from mitochondria to the cytosol triggers Apaf-1 apoptosome formation and subsequent caspase activation. This process can be recapitulated using recombinant Apaf-1 and CC in the presence of nucleotides ATP or dATP [(d)ATP] or using fresh cytosol and CC without the need of exogenous nucleotides. Surprisingly, we found that stored cytosols failed to support CC-initiated caspase activation. Storage of cytosols at different temperatures led to the loss of all (deoxy)nucleotides including (d)ATP. Addition of (d)ATP to such stored cytosols partially restored CC-initiated caspase activation. Nevertheless, CC could not induce complete caspase-9/3 activation in stored cytosols, even with the addition of (d)ATP, despite robust Apaf-1 oligomerization. The Apaf-1 apoptosome, which functions as a proteolytic-based molecular timer appeared to be defective as auto-processing of recruited procaspase-9 was inhibited. Far Western analysis revealed that procaspase-9 directly interacted with Apaf-1 and this interaction was reduced in the presence of physiological levels of ATP. Co-incubation of recombinant Apaf-1 and procaspase-9 prior to CC and ATP addition inhibited CC-induced caspase activity. These findings suggest that in the absence of nucleotide such as ATP, direct association of procaspase-9 with Apaf-1 leads to defective molecular timer, and thus, inhibits apoptosome-mediated caspase activation. Altogether, our results provide novel insight on nucleotide regulation of apoptosome.
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Affiliation(s)
- Honghao Zhang
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York, United States of America
| | - Raghu Gogada
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York, United States of America
| | - Neelu Yadav
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York, United States of America
| | - Ravi K. Lella
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York, United States of America
| | - Mark Badeaux
- Department of Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, Texas, United States of America
| | - Mary Ayres
- Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - Varsha Gandhi
- Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - Dean G. Tang
- Department of Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center, Smithville, Texas, United States of America
| | - Dhyan Chandra
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York, United States of America
- * E-mail:
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3
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Nitani N, Yadani C, Yabuuchi H, Masukata H, Nakagawa T. Mcm4 C-terminal domain of MCM helicase prevents excessive formation of single-stranded DNA at stalled replication forks. Proc Natl Acad Sci U S A 2008; 105:12973-8. [PMID: 18753627 PMCID: PMC2529087 DOI: 10.1073/pnas.0805307105] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2008] [Indexed: 11/18/2022] Open
Abstract
The minichromosome maintenance (MCM) helicase, composed of subunits Mcm2-7, is essential for the initiation and elongation phases of DNA replication. Even when DNA synthesis is blocked, MCM continues DNA unwinding to some extent for activation of the replication checkpoint and then stops. However, the mechanism of regulation of MCM-helicase activity remains unknown. Here, we show that truncation of the Mcm4 C-terminal domain (CTD) in fission yeast results in hypersensitivity to replication block caused by dNTP depletion. The truncation mcm4-c84 does not affect the activation of the replication checkpoint pathway but delays its attenuation during recovery from replication block. Two dimensional gel electrophoresis showed that mcm4-c84 delays the disappearance of replication intermediates, indicating that the Mcm4 CTD is required for efficient recovery of stalled replication forks. Remarkably, chromatin immunoprecipitation revealed that mcm4-c84 brings about an increase rather than a decrease in the association of the single-stranded DNA-binding protein RPA to stalled forks, and MCM and the accessory complex GINS are unaffected. These results suggest that the Mcm4 CTD is required to suspend MCM-helicase activity after the formation of single-stranded DNA sufficient for checkpoint activation.
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Affiliation(s)
- Naoki Nitani
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Chie Yadani
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Hayato Yabuuchi
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Hisao Masukata
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
| | - Takuro Nakagawa
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
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Abstract
We propose that the lethality of commonly used anticancer drugs, e.g., methotrexate and cis-platinum are due, at least in part, to an increase of the E2F-1-mediated apoptotic cascade. The drugs directly or indirectly decrease deoxynucleoside triphosphates. The E2F family acts to provide control of S phase by transcribing genes required for deoxynucleoside triphosphate and DNA synthesis. Thus, a mechanism for control of E2F-1 is essential, a signal safeguarding against aberrant or uncontrolled cell proliferation. We have proposed a feedback control by NTPs that down-regulates E2F-1. Here, we provide evidence in support of this hypothesis.
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Affiliation(s)
- Ajin Wang
- ArQule Biomedical Institute, ArQule Inc., Woburn, Massachusetts, USA
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5
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Abstract
BACKGROUND We evaluated the effects of nucleosides (NS) and nucleotides (NT) on the rejection of rat allogeneic small intestinal transplants. METHODS A 2-cm segment of jejunum from fetal Fischer rats (RT-1(lvl)) was transplanted at day 19 of gestation into the abdominal wall of 7-week-old Lewis rats (RT-1(l)) by a nonvascular technique. Two weeks before transplantation, recipient rats were separated into an NS-NT-free group and an NS-NT-supplemented group. At 2 days after transplantation, histologic study of the grafts was performed with hematoxylin-eosin staining and interleukin-2 (IL-2) production estimated in recipient blood using an ELISA method. The morphologic findings were graded in a blind fashion on a scale of 0 to 4, with 0 indicating an intact intestinal structure. RESULTS Mean plasma IL-2 levels of the NS-NT-free group were significantly lower than those of the NS-NT-supplemented group. The mean rejection score of the NS-NT-free group was also significantly lower than that of the NS-NT-supplemented group. CONCLUSIONS Administration of an NS-NT-free diet reduces acute rejection in rat small intestinal transplantations.
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Affiliation(s)
- K Ogita
- Department of Pediatric Surgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
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6
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Abstract
It is well known that inappropriate nutrient intake accounts for the maintenance of the immunological equilibrium, in humans and animals. Vitamins, elements, lipids, proteins and nucleic acids play an important role in the regulation of cellular and humoral immune responses since single or multiple deficits of these food components have been shown to cause immune abnormalities. For instance, in the course of protein-calorie malnutrition bacterial and/or viral infections represent the major cause of death. Ageing is characterized by a decline of many immune functions, and this process is called immunosenescence. Here, we report novel findings on the inability of superantigens to activate old CD8+, natural killer and B cells, as an expression of cell amnesia. In the elderly, this lack of activation could lead to lethal effects in the case of severe staphylococcal infections. Quite interestingly, recent findings outlined some similarities between human immune deficiency virus (HIV)-1 infection and ageing in terms of immune changes. The model of HIV-infection may be useful for the interpretation of ageing mechanisms and possible therapeutical interventions. Finally, the role of nutrition in different pathological conditions and the use of medical foods for correcting of immune deficits will be described.
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Affiliation(s)
- L Amati
- Scientific Institute for Digestive Diseases, Castellana Grotte, Bari, Italy.
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Sandoval RM, Bacallao RL, Dunn KW, Leiser JD, Molitoris BA. Nucleotide depletion increases trafficking of gentamicin to the Golgi complex in LLC-PK1 cells. Am J Physiol Renal Physiol 2002; 283:F1422-9. [PMID: 12388419 DOI: 10.1152/ajprenal.00095.2002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Having shown rapid trafficking of aminoglycosides to the Golgi complex in cell culture, we focused on the injurious interaction that occurs when gentamicin administration is preceded by renal ischemia. Using Texas red-labeled gentamicin as a tracer, we determined that 15 min of cellular nucleotide depletion did not significantly increase subsequent uptake. However, cells previously depleted of nucleotides accumulated significantly more Texas red-labeled gentamicin within a dispersed Golgi complex. Using Ricinus communis and Lens culinaris lectins, which label specific compartments of the Golgi complex (trans-Golgi network/trans and medial/cis compartments, respectively), we determined that the medial/cis compartment dispersed after 15 min of nucleotide depletion but the trans-Golgi network/trans compartment remained unaffected. An increase in the number of cells exhibiting disrupted medial/cis-Golgi morphology after repletion in physiological media containing gentamicin was also seen. In summary, the increase in nephrotoxicity seen when ischemia precedes aminoglycoside uptake may be part of a complex mechanism initially involving increased Golgi accumulation and prolonged Golgi dispersion. The Golgi complex must then endure the effects of gentamicin accumulated in larger quantities in an aberrant physiological state.
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Affiliation(s)
- Ruben M Sandoval
- Department of Medicine, Division of Nephrology, Indiana University School of Medicine and Roudebush Veterans Administration Medical Center, Indianapolis, Indiana 46202, USA
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Paulson TG, Almasan A, Brody LL, Wahl GM. Gene amplification in a p53-deficient cell line requires cell cycle progression under conditions that generate DNA breakage. Mol Cell Biol 1998; 18:3089-100. [PMID: 9566927 PMCID: PMC110691 DOI: 10.1128/mcb.18.5.3089] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Amplification of genes involved in signal transduction and cell cycle control occurs in a significant fraction of human cancers. Loss of p53 function has been proposed to enable cells with gene amplification to arise spontaneously during growth in vitro. However, this conclusion derives from studies employing the UMP synthesis inhibitor N-phosphonacetyl-L-aspartate (PALA), which, in addition to selecting for cells containing extra copies of the CAD locus, enables p53-deficient cells to enter S phase and acquire the DNA breaks that initiate the amplification process. Thus, it has not been possible to determine if gene amplification occurs spontaneously or results from the inductive effects of the selective agent. The studies reported here assess whether p53 deficiency leads to spontaneous genetic instability by comparing cell cycle responses and amplification frequencies of the human fibrosarcoma cell line HT1080 when treated with PALA or with methotrexate, an antifolate that, under the conditions used, should not generate DNA breaks. p53-deficient HT1080 cells generated PALA-resistant variants containing amplified CAD genes at a frequency of >10(-5). By contrast, methotrexate selection did not result in resistant cells at a detectable frequency (<10(-9)). However, growth of HT1080 cells under conditions that induced DNA breakage prior to selection generated methotrexate-resistant clones containing amplified dihydrofolate reductase sequences at a high frequency. These data demonstrate that, under standard growth conditions, p53 loss is not sufficient to enable cells to produce the DNA breaks that initiate amplification. We propose that p53-deficient cells must proceed through S phase under conditions that induce DNA breakage for genetic instability to occur.
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Affiliation(s)
- T G Paulson
- Department of Biology, University of California, San Diego, La Jolla 92093, USA
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9
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Abstract
The aim of the present study was to investigate the influence of dietary nucleotides on liver morphology. Adult rats were fed for 21 d on a nucleotide-containing diet or the same diet free of nucleotides. Liver sections were examined by light and transmission electron microscopy, as well as for nucleic acid and protein contents. Morphometric analysis was performed for different variables. Deprivation of dietary nucleotides resulted in a reduction in hepatocyte nuclear and nucleolar areas as well as in nuclear chromatin condensation. In addition, the rough endoplasmic reticulum was reduced, as were ribosome association and abundance, whereas fat accumulated. These findings portray dietary nucleotides as required nutrients for the liver under normal physiological conditions and suggest that an inadequate supply of nucleotides for a certain period of time has transient negative effects on liver ultrastructure and function.
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Affiliation(s)
- A T López-Navarro
- Department of Biochemistry, Faculty of Pharmacy, University of Granada, Spain
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10
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López-Navarro AT, Ortega MA, Peragón J, Bueno JD, Gil A, Sánchez-Pozo A. Deprivation of dietary nucleotides decreases protein synthesis in the liver and small intestine in rats. Gastroenterology 1996; 110:1760-9. [PMID: 8964401 DOI: 10.1053/gast.1996.v110.pm8964401] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND & AIMS Dietary nucleotides are reported to influence the growth and functioning of the liver and small intestine. The aim of this study was to examine the mechanism by which nucleotides exert their effects in these tissues by assessing protein synthesis activity and related parameters in the presence or absence of dietary nucleotides. METHODS Rats were fed a purified diet with or without nucleotides for 10 days. Fractional protein synthesis rate, RNA and DNA concentrations, polysome size distribution, and number of ribosomes were assessed. RESULTS Fractional protein synthesis rates of the liver and small intestine were lower in the nucleotide-deprived group than in the control group. In the liver, RNA concentration was also lower in the nucleotide-deprived group, but values in the small intestine were similar in the two groups. In the liver, deprivation of nucleotides resulted in a reduction in the number of ribosomes and in polysome breakdown. Protein and DNA concentrations did not vary in the liver; however, the concentration of DNA was lower in the small intestine of the nucleotide-deprived group than in the control group. CONCLUSIONS Dietary nucleotides can modulate protein synthesis in the liver and small intestine as a result of tissue-specific nucleic acid changes.
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Affiliation(s)
- A T López-Navarro
- Department of Biochemistry and Molecular Biology, University of Granada, Spain
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Gmitter D, Brostrom CO, Brostrom MA. Translational suppression by Ca2+ ionophores: reversibility and roles of Ca2+ mobilization, Ca2+ influx, and nucleotide depletion. Cell Biol Toxicol 1996; 12:101-13. [PMID: 8738479 DOI: 10.1007/bf00143360] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The divalent cation selective ionophores A23187 and ionomycin were compared for their effects on the Ca2+ contents, nucleotide contents, and protein synthetic rates of several types of cultured cells. Both ionophores reduced amino acid incorporation by approximately 85% at low concentrations (50-300 nmol/L) in cultured mammalian cells without reducing ATP or GTP contents. At these concentrations A23187 and ionomycin each promoted substantial Ca2+ efflux, whereas at higher concentrations a large influx of the cation was observed. Ca2+ influx occurred at lower ionophore concentrations and to greater extents in C6 glioma and P3X63Ag8 myeloma than in GH3 pituitary cells. The ATP and GTP contents of the cells and their ability to adhere to growth surfaces declined sharply at ionophore concentrations producing increased Ca2+ influx. Prominent reductions of nucleotide contents occurred in EGTA-containing media that were further accentuated by extracellular Ca2+. Ionomycin produced more Ca2+ influx and nucleotide decline than comparable concentrations of A23187. The inhibition of amino acid incorporation and mobilization of cell-associated Ca2+ by ionomycin were readily reversed in GH3 cells by fatty acid-free bovine serum albumin, whereas the effects of A23187 were only partially reversed. Amino acid incorporation was further suppressed by ionophore concentrations depleting nucleotide contents. Mitochondrial uncouplers potentiated Ca2+ accumulation in response to both ionophores. At cytotoxic concentrations Lubrol PX abolished protein synthesis but did not cause Ca2+ influx. Nucleotide depletion at high ionophore concentrations is proposed to result from increased plasmalemmal Ca2+-ATPase activity and dissipation of mitochondrial proton gradients and to cause intracellular Ca2+ accumulation. Increased Ca2+ contents in response to Ca2+ ionophores are proposed as an indicator of ionophore-induced cytotoxicity.
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Affiliation(s)
- D Gmitter
- Department of Pharmacology, UMDNJ, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA
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Jyonouchi H, Sun S, Zhang-Shanbhag L, Yokoyama H. Polynucleotides compensate for impaired T-dependent antibody production induced in C57B1/6 mice by a nucleotide-free diet both in vivo and in vitro, but a mononucleotide-nucleoside mixture is effective only in vivo. J Nutr 1995; 125:1578-86. [PMID: 7540201 DOI: 10.1093/jn/125.6.1578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Actions of nucleotides on in vitro humoral immune responses were studied in mice fed a nucleotide-free diet, a nucleotide-free diet plus a mononucleotide-nucleoside mixture or a nucleotide-free diet plus yeast RNA (polynucleotides). Cultured spleen cells from mice fed a nucleotide-free diet produced fewer numbers of antibody-secreting cells in response to a T-dependent antigen, compared with those from controls fed nucleotide-supplemented diets. Immunoglobulin M concentrations in these supernatants were significantly lower in cultured cells from mice fed the nucleotide-free diet or the nucleotide-free diet plus the mononucleotide/nucleoside mixture compared with concentrations in cells from mice fed the nucleotide-free diet plus RNA. Concanavalin A-potentiated cytokine (interleukin-4 and interleukin-5) production by purified T helper cells was also lower in cultured cells from mice fed a nucleotide-free diet than in those from mice fed nucleotide-supplemented diets. In vivo supplementation with the mononucleotide/nucleoside mixture restored impaired in vitro antibody and concanavalin A-potentiated cytokine production in mice fed a nucleotide-free diet. However, addition of RNA to the culture enhanced antibody production in spleen cells from mice of all diet groups. Supplementing the culture with RNA did not enhance mitogen-potentiated cytokine production. This in vitro action of RNA was retained after the removal of oligonucleotides (molecular weight < 1000), but was reduced by modification of bases and cleavage of phosphodiester bonds of RNA. Thus the in vitro action of RNA is mainly attributed to polynucleotides, indicating their potential role in modulation of local humoral immune responses in the body.
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Affiliation(s)
- H Jyonouchi
- Department of Pediatrics, University of Minnesota, Minneapolis 55455, USA
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13
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Abstract
We describe the changes of several brush-border enzymatic activities in different subpopulations of epithelial cells, separated sequentially from the villus tip-to-crypt axis of the small intestine, induced by deprivation of dietary nucleotides for different periods of time in adult rats. Deprivation of dietary nucleotides lead to a decrease in the content and specific activity of alkaline phosphatase, leucine-aminopeptidase, maltase, sucrase and lactase in the villus tip, but had little effect on the crypt zone. The effect of the nucleotide deprivation on the enzymatic activity progressively increased towards the tip of the villus. Since these enzymes are maturation markers of the intestinal cells, these results support the idea that dietary nucleotides affect the maturation status of small-intestine epithelium.
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Affiliation(s)
- M A Ortega
- Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, University of Granada, Spain
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14
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Affiliation(s)
- F B Rudolph
- Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77251-1892
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15
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Abstract
Historical accounts and recent epidemiologic studies have suggested a mutually aggravating relationship between malnutrition and infection. In protein-energy malnutrition, there is a significant impairment of several aspects of immunity, including cell-mediated immune responses, secretory immunoglobulin A antibody production, phagocyte function, complement system, antibody affinity and cytokine production. Several micronutrients play a crucial role in maintenance of optimum immune responses. On the other hand, excessive intake of nutrients also impairs immunity. Animals fed diets lacking in nucleotides have lower immune responses than controls but there is no enhancement of immunity when the diet contains large amounts of nucleotides. These observations have considerable practical importance in terms of designing feeding formulas.
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Affiliation(s)
- R K Chandra
- Department of Pediatrics, Memorial University of Newfoundland, Canada
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16
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Solaini G, Baracca A, Parenti Castelli G, Strambini GB. Tryptophan phosphorescence as a structural probe of mitochondrial F1-ATPase epsilon-subunit. Eur J Biochem 1993; 214:729-34. [PMID: 8319682 DOI: 10.1111/j.1432-1033.1993.tb17974.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We report the detection of tryptophan phosphorescence emission from the sole residue in the epsilon-subunit of the bovine heart mitochondrial F1-ATPase complex. The phosphorescence spectrum, intensity and decay kinetics have been measured over the temperature range 160-273 K. The fine structure in the phosphorescence spectrum at low temperature, with the 0-0 vibrational band centered at 411 nm, reveals the hydrophobic nature of the chromophore's environment. Both the large width of the 0-0 vibrational band and the heterogeneous decay kinetics in fluid solution emphasize the existence of multiple conformations of the epsilon-subunit, structures which are rather stable as they do not interconvert in the millisecond time scale. Further, from the relatively long triplet lifetime at 273 K, it is possible to infer the existence of a tight, rigid core in the structure of the epsilon-subunit. Under subunit-dissociating conditions (6 M urea), the spectrum at 160 K undergoes a slight blue shift but since the phosphorescence lifetime, at all temperatures, is similar or longer than in the absence of dissociant, we conclude that dissociation does not lead to solvent exposure of the tryptophanyl side-chain. This conclusion is supported by the results obtained at 273 K by dissociating F1 in the presence of 0.3 M guanidine hydrochloride. Phosphorescence lifetimes indicate that 6 M urea leads to a more compact structure of the epsilon-subunit, whereas the opposite occurs when Mg-ATP is added to nucleotide-depleted F1. These spectroscopic changes establish unequivocally that the binding of the adenine nucleotide to the enzyme is accompanied by conformational changes involving the epsilon-subunit.
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Affiliation(s)
- G Solaini
- Scuola Superiore di Studi Universitari e di Perfezionamento, S. Anna, Pisa, Italy
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17
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Kulkarni A, Fanslow W, Higley H, Pizzini R, Rudolph F, Van Buren C. Expression of immune cell surface markers in vivo and immune competence in mice by dietary nucleotides. Transplant Proc 1989; 21:121-4. [PMID: 2705219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- A Kulkarni
- Department of Surgery, University of Texas Medical School, Houston 77030
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18
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RUECKERT RR, MUELLER GC. Studies on unbalanced growth in tissue culture. I. Induction and consequences of thymidine deficiency. Cancer Res 1960; 20:1584-91. [PMID: 13744520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/24/2023]
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