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Söderström KO. Nucleolar fragmentation in the rat pachytene spermatocytes and the Sertoli cells caused by alpha-amanitin. Hereditas 2009; 94:171-7. [PMID: 7298350 DOI: 10.1111/j.1601-5223.1981.tb01750.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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2
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Pession A, Farabegoli F, Treré D, Novello F, Montanaro L, Sperti S, Rambelli F, Derenzini M. The Ag-NOR proteins and transcription and duplication of ribosomal genes in mammalian cell nucleoli. Chromosoma 1991; 100:242-50. [PMID: 1711437 DOI: 10.1007/bf00344158] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The relationship between the Ag-NOR (silver-stained Nucleolar Organizer Region) proteins and the functional-structural organization of the nucleolar ribosomal chromatin was studied in regenerating and cortisol-stimulated rat hepatocytes. Statistical analysis of Ag-NOR proteins, carried out with an automated image analyzer, indicated that in regenerating rat hepatocytes the quantity of Ag-NOR proteins mainly increased between the 4th and 12th h of regeneration, reaching a level twice that of resting hepatocytes. Also the synthesis of pre-ribosomal RNA (pre-rRNA) was stimulated after the 4th h of regeneration. Cycloheximide administered to rats at a dose of 0.025 mg/100 g body weight (bw) prevented any increase in Ag-NOR proteins but did not hinder the stimulation of pre-rRNA synthesis. In 8 h cortisol-stimulated hepatocytes no significant change in amount of Ag-NOR protein was observed whereas pre-rRNA synthesis was highly increased as in 12 h regenerating hepatocytes. These results indicated that in rat hepatocytes Ag-NOR proteins and stimulation of pre-rRNA synthesis are not related. The relationship between the Ag-NOR proteins and the distribution of the completely extended intranucleolar ribosomal chromatin was also studied in regenerating rat hepatocytes. At 12 h after partial hepatectomy an increased amount of completely extended ribosomal chromatin was observed, contemporaneously with an increased quantity of Ag-NOR proteins. These ribosomal chromatin changes preceded the beginning of DNA synthesis and were prevented by cycloheximide-induced inhibition of protein synthesis.
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Affiliation(s)
- A Pession
- Dipartimento di Patologia Sperimentale, Università di Bologna, Italy
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Derenzini M, Pession A, Farabegoli F, Trerè D, Badiali M, Dehan P. Relationship between interphasic nucleolar organizer regions and growth rate in two neuroblastoma cell lines. THE AMERICAN JOURNAL OF PATHOLOGY 1989; 134:925-32. [PMID: 2705511 PMCID: PMC1879788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The relationship between the quantity of silver-stained interphasic nucleolar organizer regions (NORs) and nuclear synthetic activity, caryotype, and growth rate was studied in two established neuroblastoma cell lines (CHP 212 and HTB 10). Statistical analysis of silver-stained NORs revealed four times as many in CHP 212 cells compared with HTB 10 cells. No difference was observed in the ribosomal RNA synthesis between the two cell lines. The caryotype index was 1.2 for CHP 212 and 1.0 for HTB 10 cells. The number of chromosomes carrying NORs and the quantity of ribosomal genes was found to be the same for the two cell lines. Doubling time of CHP 212 cells was 20 hours compared with 54 hours for HTB 10 cells. In CHP 212 cells bindering of cell duplication by serum deprivation induced a progressive lowering (calculated at 48, 72, and 96 hours) of the quantity of silver-stained interphasic NORs. Recovery of duplication by new serum addition induced, after 24 hours, an increase of the quantity of silver-stained interphasic NORs up to control levels. In the light of available data, these results indicate that the quantity of interphasic NORs is strictly correlated only to the growth rate of the cell.
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Affiliation(s)
- M Derenzini
- Dipartimento di Patologia Sperimentale, University of Bologna, Italy
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4
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Derenzini M, Farabegoli F, Pession A, Novello F. Spatial redistribution of ribosomal chromatin in the fibrillar centres of human circulating lymphocytes after stimulation of transcription. Exp Cell Res 1987; 170:31-41. [PMID: 3569433 DOI: 10.1016/0014-4827(87)90114-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
We have studied the distributional changes of the completely extended ribosomal chromatin present in the fibrillar centres of resting human lymphocytes after phytohemagglutinin (PHA) treatment. In thin sections of resting lymphocytes selectively stained for DNA, the extended non-nucleosomal chromatin was located in a solitary, large agglomerate which corresponds to the solitary, large fibrillar centre observed in uranium-lead-stained sections. At 20 h after PHA stimulation the ribosomal chromatin agglomerate appeared to be fragmented into smaller agglomerates which correspond to numerous fibrillar centres surrounded by a thick rim of dense fibrillar component. The mean area of ribosomal chromatin agglomerates from resting lymphocytes was found to be 0.772 mu 2 + 0.125 SD, whereas in stimulated lymphocytes it was found to be 0.184 mu 2 + 0.052 SD. At 20 h after PHA treatment ribosomal RNA (rRNA) synthesis was 8-fold greater than the control value, whereas DNA synthesis had not started. These results indicate that ribosomal chromatin of resting lymphocyte fibrillar centres contains transcribable sequences, temporally not expressed.
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5
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Ternell M, Lönnroth C, Lundholm K. Nuclear RNA polymerase activity in tumor-host livers. THE AMERICAN JOURNAL OF PHYSIOLOGY 1985; 249:E461-9. [PMID: 2415003 DOI: 10.1152/ajpendo.1985.249.5.e461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
This study has evaluated changes in RNA synthesis in livers under the distant influence of a malignant tumor. A transplantable-induced sarcoma (MCG 101), transplanted on inbred adult mice (C57BL/6J), was used. Activities of DNA-dependent RNA polymerase (EC 2.7.7.6) were measured in relation to RNA content and translational activity. Liver nuclei from freely fed sarcoma-bearing mice had increased RNA synthesis. As a consequence of this, RNA content per DNA was increased in liver tissue. This was independent of depressed food intake and malnutrition. Elevated RNA synthesis, proportional to the tumor burden was due to an increased proportion of chromatin-engaged RNA polymerase I and II activities. RNA polymerase III activity (template-engaged form) was unchanged when evaluated in isolated nuclei, but appeared to be increased in partially purified extracts of nuclei. RNA content in tumor-host liver was a composite of increased levels of rRNA and tRNA, whereas the levels of poly(A)+ mRNA could not be measured as increased. Overall translational activities in vitro of mRNA from liver tissue of tumor-bearing, pair-weighed, and freely fed tumor-free controls were qualitatively and quantitatively different. mRNA from tumor-bearing mice directed an increased synthesis, particularly of larger proteins (above 55,000 daltons) compared with control animals. The results support the conclusion that previous evidence of elevated net protein synthesis in tumor-host liver is accompanied by increased transcription of genes coding for RNA and also for some or several hepatic proteins.
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Nicoloff H, Rieger R. Mutations in rDNA : 3. Modulatory action of α-amanitin on aberration induction in nucleolus organizer regions. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 1985; 70:178-184. [PMID: 24254177 DOI: 10.1007/bf00275319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/1984] [Accepted: 09/04/1984] [Indexed: 06/02/2023]
Abstract
The action of α-amanitin, an inhibitor of RNA synthesis, on the induction by hydroxyurea (HU) of chromosomal aberrations in nucleolus organizer regions of barley was studied. The data obtained show that α-amanitin can effectively modify aberration induction in rDNA. Administered before mutagen treatment or in combination with the mutagen, the toxin significantly decreased the HU-induced aberration frequencies in NORs. The data obtained provide further evidence that α-amanitin is an effective modulator of aberration induction in NORs either by interfering with RNA synthesis or by modifying chromatin structure.
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Affiliation(s)
- H Nicoloff
- Zentralinstitut für Genetik und Kulturpflanzenforschung, DDR-4325, Gatersleben, German Democratic Republic
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Sanders DA. Self-transcription: RNA polymerase transcription of its own genes, and its role in cellular differentiation and cell cycling. J Theor Biol 1984; 106:171-82. [PMID: 6708566 DOI: 10.1016/0022-5193(84)90017-1] [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: 01/21/2023]
Abstract
The concept of RNA polymerase self-transcription, where eukaryotic RNA polymerase II and prokaryotic holoenzyme are responsible for transcription of their own genes, would give these enzymes a unique role in the cellular transcriptional and translational machinery. This self-transcriptional ability would equip a cell with an exquisite mechanism of autogenous regulation for the appearance of these transcriptional units. Such a mechanism could allow layering of other transcriptional control pathways upon the RNA polymerase self-transcriptional pathway, thus forming a complex array of mechanisms to regulate transcription of genes concerned with cellular differentiation and cell cycling. It is proposed that RNA polymerase self-transcription is the central control point of gene expression in cellular differentiation and for cell cycling, thus fulfilling the role of an intrinsic biological clock.
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Stoykova AS, Dudov KP, Dabeva MD, Hadjiolov AA. Different Rates of Synthesis and Turnover of Ribosomal RNA in Rat Brain and Liver. J Neurochem 1983; 41:942-9. [PMID: 6555219 DOI: 10.1111/j.1471-4159.1983.tb09038.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The kinetics of in vivo labeling of cellular free UMP and nucleolar, nucleoplasmic, and cytoplasmic rRNA with [14C]orotate in rat brain and liver were investigated. Evaluation of the experimental data shows: (a) The rate of nucleolar precursors of ribosomal RNA (pre-rRNA) synthesis and the deduced rate of ribosome formation in brain is about fivefold lower than in liver and corresponds to 220-260 ribosomes/min/nucleus. (b) The lower rate of in vivo pre-rRNA synthesis is correlated with a lower activity of RNA polymerase I in isolated brain nuclei. (c) The half-lives of nucleolar rRNA in brain and liver are 210 and 60 min, respectively, thus showing a slower rate of processing of pre-rRNA in brain nucleoli. (d) The nucleo-cytoplasmic transport of ribosomes in brain is also markedly slower than in liver and reflects the lower rates of synthesis and processing of pre-rRNA. (e) Cytoplasmic ribosomes in brain and liver turn over with half-lives of about 6 and 4 days, respectively. It is concluded that the markedly lower rate of ribosome biogenesis in brain is specified mainly at the level of transcription of rRNA genes.
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Derenzini M, Hernandez-Verdun D, Pession A, Novello F. Structural organization of chromatin in nucleolar organizer regions of nucleoli with a nucleolonema-like and compact ribonucleoprotein distribution. JOURNAL OF ULTRASTRUCTURE RESEARCH 1983; 84:161-72. [PMID: 6632052 DOI: 10.1016/s0022-5320(83)90127-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
We have studied the relationship between the structural organization of intranucleolar chromatin and fibrillar nucleolar structures, fibrillar centers, and RNP fibrillar component, which are the interphase counterpart of metaphase nucleolar organizer regions (NORs), in regenerating rat hepatocytes and in a human tumor cell line (TG cells). These two cell types were characterized by a nucleolonema-like and compact nucleolar RNP distribution, respectively. We found that, in sections selectively stained for DNA, the intranucleolar chromatin composed of extended, nonnucleosomal DNA filaments formed roundish agglomerates with a spatial distribution which was superimposable on that of the fibrillar centers and the RNP fibrillar component around them and on sites of the silver reaction in samples selectively stained for Ag-NOR proteins. The agglomerates of extended nonnucleosomal DNA filaments were small and numerous in regenerating hepatocyte nucleoli, in which the RNP components had a nucleolonema-like distribution, whereas they were large and few in TG cell nucleoli, in which the RNP components showed a compact organization. Since the pattern of ribosomal RNA synthesis and processing was similar in the two cell types, a model was proposed in which the difference in size and shape of the agglomerates of extended DNA might be responsible for the different structural organization of the RNP components.
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Dudov KP, Dabeva MD. Post-transcriptional regulation of ribosome formation in the nucleus of regenerating rat liver. Biochem J 1983; 210:183-92. [PMID: 6552185 PMCID: PMC1154204 DOI: 10.1042/bj2100183] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Kinetic experiments on RNA labelling in vivo with [14C]orotate were performed with normal and 12h-regenerating rat liver. The specific radioactivities of nucleolar, nucleoplasmic and cytoplasmic rRNA species were analysed by computer according to the models of rRNA processing and nucleo-cytoplasmic migration given previously [Dudov, Dabeva, Hadjiolov & Todorov, Biochem. J. (1978) 171, 375-383]. The rates of formation and the half-lives of the individual pre-rRNA and rRNA species were determined in both normal and regenerating liver. The results show clearly that the formation of ribosomes in regenerating rat liver is post-transcriptionally activated: (a) the half-lives of all the nucleolar pre-rRNA and rRNA species are decreased by 30% on average; (b) the pre-rRNA processing is directed through the shortest maturation pathway: 45 S leads to 32 S + 18 S leads to 28 S; (c) the nucleo-cytoplasmic transfer of ribosomes is accelerated. As a consequence, the time for formation and appearance of ribosomes in the cytoplasm is shortened 1.5-fold for the large and 2-fold for the small subparticle. A new scheme for endonuclease cleavage of 45 S pre-rRNA is proposed, which explains the alterations in pre-rRNA processing in regenerating liver. Its validity for pre-rRNA processing in other eukaryotes is discussed. It is concluded that: (i) the control sites in the intranucleolar formation of 28 S and 18 S rRNA are the immediate precursor of 28 S rRNA, 32 S pre-rRNA, and the primary pre-rRNA, 45 S pre-rRNA, respectively; (ii) the limiting step in the post-transcriptional stages of ribosome biogenesis is the pre-rRNA maturation.
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Dudov KP, Hadjiolova KV, Kermekchiev MB, Stanchev BS, Hadjiolov AA. A 12 S precursor to 5.8 S rRNA associated with rat liver nucleolar 28 S rRNA. ACTA ACUST UNITED AC 1983; 739:79-84. [PMID: 6550497 DOI: 10.1016/0167-4781(83)90047-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The pre-rRNA and rRNA components of rat and mouse liver nucleolar RNA were analysed. It was shown that upon denaturation, part of the 32 S pre-rRNA is converted into 28 S rRNA and 12 S RNA. The 12 S RNA from mouse (Mr, 0.36 X 10(6)) is larger than the one from rat (Mr, 0.32 X 10(6). The 12 S RNA chain is intact and resists denaturation treatment. The non-covalent binding of this RNA with nucleolar 28 S rRNA is stronger than that of 5.8 S rRNA with 28 S rRNA. Hybridization with a rat internal-transcribed spacer rDNA fragment identifies 12 S RNA as corresponding to the 5'-end non-conserved segment of 32 S pre-rRNA, including 5.8 S rRNA. The significance of the formation of a 12 S precursor to 5.8 S rRNA in the biogenesis of ribosomes in mammalian cells is discussed.
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12
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Derenzini M, Pession A, Betts-Eusebi CM, Novello F. Relationship between the extended, non-nucleosomal intranucleolar chromatin in situ and ribosomal RNA synthesis. Exp Cell Res 1983; 145:127-43. [PMID: 6852122 DOI: 10.1016/s0014-4827(83)80015-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In the present study we have investigated the relationship between the structure of intranucleolar chromatin in situ and the synthesis of rRNA. Using thin sections selectively stained for DNA we observed that intranucleolar chromatin of cortisol-stimulated rat hepatocytes consisted of clumps and fibres, both showing a nucleosomal configuration, and by loose agglomerates of extended DNA filaments, with a thickness of 2-3 nm, which never formed nucleosomal structures. After inhibition of rRNA synthesis by actinomycin D, the agglomerates of extended DNA filaments without nucleosomal configuration were noticed to be still present even at 3 h after drug treatment. In human resting lymphocytes, with a very low rate of rRNA synthesis, a large roundish, loose agglomerate of DNA filaments without nucleosomal configuration was found in the central zone of the nucleolar body. After a 16-fold increase in rRNA synthesis induced by a 48-h stimulation with phytohemagglutinin (PHA) the loose agglomerates appeared to be more numerous, but markedly reduced in size. We concluded that the extended non-nucleosomal configuration is a permanent feature of intranucleolar loose chromatin agglomerates and not a consequence of transcriptional activity.
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Olszanska B, Kludkiewicz B. The effect of transcription inhibitors on early development of the avian embryo. CELL DIFFERENTIATION 1983; 12:115-20. [PMID: 6825178 DOI: 10.1016/0045-6039(83)90064-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The effect of transcription [actinomycin D, 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), alpha-amanitin] and translation inhibitors (cycloheximide, puromycin) on quail embryo development was investigated under in vitro conditions. The gastrulation process seemed to proceed normally in the presence of transcription inhibitors in the medium but the translation inhibitors stopped development and caused complete degeneration of the embryos.
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Dabeva MD, Dudov KP. Transcriptional control of ribosome production in regenerating rat liver. Biochem J 1982; 208:101-8. [PMID: 6925448 PMCID: PMC1153935 DOI: 10.1042/bj2080101] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Kinetic experiments of labelling in vivo with [14C]orotate of cellular free UMP and/or UTP, nucleolar, nucleoplasmic and cytoplasmic rRNA in normal and 12 h-regenerating rat liver were performed. The specific-radioactivity curves obtained were analysed by computer and the rates of synthesis of precursor rRNA (45S pre-rRNA) and cytoplasmic 28S and 18S rRNA calculated. (a) The rates of synthesis of 45S pre-rRNA in normal and regenerating rat liver are 1400 and 3700 molecules/min per nucleus respectively; (b) the average rates of formation of mature 28S and 18S rRNA are identical with the rates of synthesis of 45S pre-rRNA in both normal and regenerating rat liver. Thus the synthesis of rRNA in 12h-regenerating rat liver is activated 2.7-fold. The analysis of rRNA synthesis in isolated nucleoli also shows a 2.7-fold stimulation of transcription in regenerating liver. It is concluded that all the 45S pre-rRNA molecules synthesized are processed and transferred as 28S and 18S rRNA in the cytoplasm, i.e. degradation (wastage) of newly synthesized ribosomes in the nucleus does not occur in both normal and regenerating rat liver. Thus the enhanced production of ribosomes in regenerating rat liver is regulated only at the transcriptional level.
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Derenzini M, Pession-Brizzi A, Novello F. Relationship between ribonucleoprotein particle, containing heterogeneous RNA and ultrastructure and function of chromatin in purified rat hepatocyte nuclei. JOURNAL OF ULTRASTRUCTURE RESEARCH 1981; 77:66-82. [PMID: 7299910 DOI: 10.1016/s0022-5320(81)80067-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Hadjiolova KV, Naydenova ZG, Hadjiolov AA. Inhibition of ribosomal RNA maturation in Friend erythroleukemia cells by 5-fluorouridine and toyocamycin. Biochem Pharmacol 1981; 30:1861-3. [PMID: 6944069 DOI: 10.1016/0006-2952(81)90026-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Derenzini M, Pession-Brizzi A, Betts-Eusebi C, Novello F. Relationship between the fine structural organization of chromatin and nucleic acid synthesis in regenerating rat hepatocytes. JOURNAL OF ULTRASTRUCTURE RESEARCH 1981; 75:229-42. [PMID: 6167740 DOI: 10.1016/s0022-5320(81)80138-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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18
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Jendrisak J. The use of alpha-amanitin to inhibit in vivo RNA synthesis and germination in wheat embryos. J Biol Chem 1980. [DOI: 10.1016/s0021-9258(18)43529-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Stoyanova BB, Dabeva MD. Ribosomal RNA precursor transcription in rat liver is not dependent on continuous synthesis of proteins. BIOCHIMICA ET BIOPHYSICA ACTA 1980; 608:358-67. [PMID: 7397190 DOI: 10.1016/0005-2787(80)90181-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The effect of inhibition of protein synthesis by cycloheximide on rRNA precursor transcription in rat liver was analyzed. Two doses of the drug were studied: low, 5 mg/kg, and high, 20 mg/kg. Both doses of cycloheximide cause rapid, complete and continuous inhibition of protein synthesis. The low dose of the antibiotic does not alter the rRNA precursor transcription for at least 4 h, while the high dose, which is lethal to rats, leads gradually to suppression of rRNA precursor synthesis. It is shown that the high dose of cycloheximide causes profound changes in the metabolism of the free nucleotides and drastic inhibition of [14C]orotate and [32P]orthophosphate uptake into the pool of free nucleotides. It is supposed that the strong side-effects of cycloheximide, rather than the cessation of protein synthesis, are responsible for the observed inhibition of rRNA precursor synthesis. It is concluded that rRNA precursor transcription is not regulated by rapidly turning-over protein(s).
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Genchev DD, Kermekchiev MB, Hadjiolov AA. Free pyrimidine nucleotide pool of Ehrlich ascites-tumour cells. Compartmentation with respect to the synthesis of heterogeneous nuclear RNA and precursors to ribosomal RNA. Biochem J 1980; 188:85-90. [PMID: 7406891 PMCID: PMC1162540 DOI: 10.1042/bj1880085] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The incorporation of [14C]orotate and [14C]uridine into UMP residues of hnRNA (heterogeneous nuclear RNA) and pre-rRNA (precursors to rRNA) of Eharlich ascites-tumour cells was compared: orotate was incorporated at a markedly higher rate into hnRNA. On the other hand, the rate of incorporation of uridine into pre-rRTNA was even somewhat higher than into hnRNA. The ratio of specific radioactivities of CMP to UMP residues in pre-rRNA and hnRNA was studied. At all times of labelling this ratio was similar for both RNA species independently of the precursor used. On addition of excess unlabelled uridine, the CMP/UMP labelling ratio in both pre-rRNA and hnRNA rose. However, this increase was much more pronounced with hnRNA. It is concluded that nuclear pyrimidine nucleotide pool for RNA synthesis is compartmentalized. The synthesis of hnRNa is supplied preferentially by the large and the small compartment, respectively. A detailed model for the cellular compartmentation of uridine nucleotide precursors to RNA is proposed.U
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Gajdardjieva KC, Dabeva MD, Hadjiolov AA. Maturation and nucleo-cytoplasmic transport of rat-liver ribosomal RNA upon D-galactosamine inhibition of transcription. EUROPEAN JOURNAL OF BIOCHEMISTRY 1980; 104:451-8. [PMID: 7363901 DOI: 10.1111/j.1432-1033.1980.tb04447.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
D-Galactosamine (250 mg/kg body weight) causes 90--95% inhibition of [14C]orotate or inorganic [32P]phosphate incorporation in vivo into rat liver nuclear RNA within 30 min. The transcription of both nucleolar and nucleoplasmic genes is inhibited to the same extent. Under these conditions, prelabbeled 45-S pre-rRNA is processed quantitatively to nuclear 28-S and 18-S rRNA. The nucleocytoplasmic transport of both 28-S and 18-S rRNA remains unaltered for about 60 min after blockage of transcription. At this stage the nucleo-cytoplasmic transport of 18-S rRNA is almost completed. It is concluded that formation and nucleo-cytoplasmic transport of ribosomes is independent of concurrent transcription of rRNA or nucleoplasmic genes. At later stages, the nucleocytoplasmic transport of 28-S rRNA is delayed and its partial degaradation in the nucleus may take place. This effect is correlated with a decreased (up to 40% of controls) labelling of nuclear proteins. However, the labelling of total cellular or microsomal proteins remains unchanged up to 3 h after D-galactosamine administration. It is suggested that the last nuclear steps of ribosome formation are dependent on the continuous supply of rapidly-labelled nuclear proteins.
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Derenzini M, Pession-Brizzi A, Novello F. Chromatin condensation in isolated rat hepatocyte nuclei induced by ribonuclease treatment. EXPERIENTIA 1980; 36:181-3. [PMID: 7371752 DOI: 10.1007/bf01953719] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Ribonuclease treatment of isolated rat hepatocyte nuclei induced a 75% solubilization in hnRNA, a reduction of the quantity of perichromatin fibrils, and a marked condensation of chromatin.
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Stoykova AS, Dabeva MD, Dimova RN, Hadjiolov AA. Ribosomal RNA precursors in neuronal and glial rat brain nuclei. J Neurochem 1979; 33:931-7. [PMID: 490165 DOI: 10.1111/j.1471-4159.1979.tb09923.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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25
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Wieland T, Faulstich H. Amatoxins, phallotoxins, phallolysin, and antamanide: the biologically active components of poisonous Amanita mushrooms. CRC CRITICAL REVIEWS IN BIOCHEMISTRY 1978; 5:185-260. [PMID: 363352 DOI: 10.3109/10409237809149870] [Citation(s) in RCA: 372] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
This review gives a comprehensive account of the molecular toxicology of the bicyclic peptides obtained from the poisonous mushrooms of the genus Amanita. The discussion of the biochemical events will be preceded by a consideration of the chemistry of the toxic peptides. The structural features essential for biological activities of both the amatoxins and the phallotoxins will be discussed, also including the most important analytical data. Similar consideration will be given to antamanide, a cyclic peptide, which counteracts phalloidin. In addition, the phallolysins, three cytolytic proteins from Amanita phalloides will be discussed. The report on the biological activity of the amatoxins will deal with the sensitivity of the different RNA-polymerases towards the toxins and with their action on various cell types. Consideration will also be given to systems in which alpha-amanitin was used and can be used as a molecular tool; in the past, many investigators used the inhibitor in molecular biology, genetics, and even in physiological research. As for the phallotoxins, discussion of the affinity of these toxins for actin is provied. Further discussion attempts to understand the course of intoxication by filling in the gap between the first molecular event, formation of microfilaments, and the various lesions in hepatocytes during the intoxication.
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Brasch K, Sinclair GD. The organization, composition and matrix of hepatocyte nuclei exposed to alpha-amanitin. VIRCHOWS ARCHIV. B, CELL PATHOLOGY 1978; 27:193-204. [PMID: 96580 DOI: 10.1007/bf02888994] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Alterations in the structure and molecular composition of avian hepatocyte nuclei were compared following administration in vivo of lethal and sub-lethal doses of alpha-amanitin. This toxin interferes with extranucleolar transcription by direct inhibition of RNA polymerase II activity. the resultant effects include: extensive condensation of chromatin, displacement of nucleoplasmic contents and fragmentation of nucleoli. Changes in nuclear morphology were quantitated by stereometry and related to variations in RNA and residual, non-histone proteins (NHP). Gross alterations in nuclear structure and depletion of RNA and NHP levels were of similar magnitude with both doses of amanitin. The effects were fully reversible, however, with a minimal dose but terminal with a lethal dose. DNA and histone protein levels remained unchanged at all stages. These results imply that the process of transciption may itself keep and/or maintain chromatin in a dispersed state, and that in the absence of transcription chromatin naturally condenses. Modification of nuclear proteins may be necessary only to maintain chromatin compacted permanently or for extended periods of time. A model of nuclear organization is proposed to incorporate these considerations and to identify the probable location of the nuclear matrix in situ.
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27
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Dabeva MD, Dudov KP, Hadjiolov AA, Stoykova AS. Quantitative analysis of rat liver nucleolar and nucleoplasmic ribosomal ribonucleic acids. Biochem J 1978; 171:367-74. [PMID: 656050 PMCID: PMC1183965 DOI: 10.1042/bj1710367] [Citation(s) in RCA: 40] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
rRNA from detergent-purified nuclei was fractionated quantitatively, by two independent methods, into nucleolar and nucleoplasmic RNA fractions. The two RNA fractions were analysed by urea/agar-gel electrophoresis and the amount of pre-rRNA (precursor of rRNA) and rRNA components was determined. The rRNA constitutes 35% of total nuclear RNA, of which two-thirds are in nucleolar RNA and one-third in nucleoplasmic RNA. The identified pre-rRNA components (45 S, 41 S, 39 S, 36 S, 32 S and 21 S) are confined to the nucleolus and constitute about 70% of its rRNA. The remaining 30% are represented by 28 S and 18 S rRNA, in a molar ratio of 1.4. The bulk of rRNA in nucleoplasmic RNA is represented by 28 S and 18 S rRNA in a molar ratio close to 1.0. Part of the mature rRNA species in nucleoplasmic RNA originate from ribosomes attached to the outer nuclear membrane, which resist detergent treatment. The absolute amount of nuclear pre-rRNA and rRNA components was evaluated. The amount of 32 S and 21 S pre-rRNA (2.9 x 10(4) and 2.5 x 10(4) molecules per nucleus respectively) is 2-3-fold higher than that of 45 S, 41 S and 36 S pre-rRNA.
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28
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Frederiksen S, Hellung-Larsen P, Gram Jensen E. The differential inhibitory effect of alpha-amanitin on the synthesis of low molecular weight RNA components in BHK cells. FEBS Lett 1978; 87:227-31. [PMID: 631339 DOI: 10.1016/0014-5793(78)80338-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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29
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Connan G, Rabotti GF. Effects of alpha-amanitin on RNA synthesis in cultured chicken fibroblasts transformed by Rous sarcoma virus. Biochimie 1978; 60:85-90. [PMID: 206293 DOI: 10.1016/s0300-9084(78)80203-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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30
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Levey IL, Brinster RL. Effects of alpha-amanitin on RNA synthesis by mouse embryos in culture. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 1978; 203:351-60. [PMID: 641476 DOI: 10.1002/jez.1402030303] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Investigations were conducted to test the effects of alpha-amanitin on RNA synthesis in preimplantation mouse embryos. Exposure of embryos in culture to 1-100 microgram/ml alpha-amanitin produced a dose- and time-dependence suppression of total RNA synthesis as measured by incorporation of [3H]uridine. Synthesis of polyadenylated RNA in blastocyst-stage embryos was abolished by alpha-amanitin-treatment at concentrations and exposure times that suppressed total RNA synthesis by less than 15%. DNA-dependent RNA polymerase activity was measured in lysates of embryos at several stages of preimplantation development. alpha-Amanitin suppressed total polymerase activity assayed under ionic conditions favorable to the detection of RNA polymerase II. Electrophoretic analyses revealed that preincubation of blastocysts in 100 microgram/ml alpha-amanitin reduced labelling of cytoplasmic 28S and 18S RNA by inhibition of both synthesis and maturation of nucleolar 45SrRNA-precursor. This action of alpha-amanitin on nucleolar RNA synthesis cannot be correlated with the minimal suppression of nucleolar RNA polymerase activity and suggests that the synthesis and processing of rRNA may be under control of nucleoplasmic gene products.
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31
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Sehgal PB, Tamm I. Halogenated benzimidazole ribosides, Novel inhibitors of RNA synthesis. Biochem Pharmacol 1978; 27:2475-85. [PMID: 365184 DOI: 10.1016/0006-2952(78)90313-1] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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32
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Sinclair GD, Brasch K. The reversible action of alpha-amanitin on nuclear structure and molecular composition. Exp Cell Res 1978; 111:1-14. [PMID: 620689 DOI: 10.1016/0014-4827(78)90230-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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33
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Hadjiolov AA, Nikolaev N. Maturation of ribosomal ribonucleic acids and the biogenesis of ribosomes. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1978; 31:95-144. [PMID: 790469 DOI: 10.1016/0079-6107(78)90006-8] [Citation(s) in RCA: 115] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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34
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Vergleichende Untersuchungen der Kernveränderungen von Rattenhepatocyten nach Actinomycin D- und α-Amanitin-Vergiftung. ACTA ACUST UNITED AC 1977. [DOI: 10.1007/bf02889123] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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35
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Gajdardjieva KC, Dabeva MD, Chelibonova-Lorer H, Hadjiolov AA. The use of D-galactosamine for a pulse-chase study of ribosomal RNA maturation in rat liver. FEBS Lett 1977; 84:48-52. [PMID: 590526 DOI: 10.1016/0014-5793(77)81054-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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36
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Dabeva MD, Petrov PT, Stoykova AS, Hadjiolov AA. Contamination of detergent-purified rat liver nuclei by cytoplasmic ribosomes. Exp Cell Res 1977; 108:467-71. [PMID: 560977 DOI: 10.1016/s0014-4827(77)80061-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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37
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Ben-Porath E, Gibson KD. Effect of RNA synthesis inhibitors on stimulation of sulfation by L-3,5,3'-triiodothyronine. Biochem Biophys Res Commun 1977; 75:311-9. [PMID: 557980 DOI: 10.1016/0006-291x(77)91044-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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38
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Connan G, Suskind G, Rabotti GF. Effect of low doses of actinomycin D on RNA synthesis in chick embryo fibroblasts transformed by Rous sarcoma virus. Biochimie 1977; 59:105-9. [PMID: 192322 DOI: 10.1016/s0300-9084(77)80093-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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39
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Dabeva MD, Dudov KP, Hadjiolov AA, Emanuilov I, Todorov BN. Intranuclear maturation pathways of rat liver ribosomal ribonucleic acids. Biochem J 1976; 160:495-503. [PMID: 1016236 PMCID: PMC1164266 DOI: 10.1042/bj1600495] [Citation(s) in RCA: 41] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The maturation of pre-rRNA (precursor to rRNA)in liver nuclei is studied by agar/ureagel electrophoresis, kinetics of labelling in vivo with [14C] orotate and electron-microscopic observation of secondary structure of RNA molecules. (1) Processing starts from primary pre-rRNA molecules with average mol. wt. 4.6X10(6)(45S) containing the segments of both 28S and 18S rRNA. These molecules form a heterogeneous peak on electrophoresis. The 28S rRNA segment is homogeneous in its secondary structure. However, the large transcribed spacer segment (presumably at the 5'-end) is heterogeneous in size and secondary structure. A minor early labelled RNA component with mol.wt. about 5.8X10(6) is reproducibly found, but its role as a pre-rRNA species remains to be determined. (2) The following intermediate pre-rRNA species are identified: 3.25X10(6) mol.wt.(41S), a precursor common to both mature rRNA species ; 2.60X10(6)(36S) and 2.15X10(6)(32S) precursors to 28S rRNA; 1.05X10(6) (21S) precursor to 18S rRNA. The pre-rRNA molecules in rat liver are identical in size and secondary structure with those observed in other mammalian cells. These results suggest that the endonuclease-cleavage sites along the pre-rRNA chain are identical in all mammalian cells. (3) Labelling kinetics and the simultaneous existence of both 36S and 21S pre-rRNA reveal that processing of primary pre-rRNA in adult rat liver occurs simultaneously by at least two major pathways: (i) 45S leads to 41S leads to 32S+21S leads to 28S+18S rRNA and (ii) 45S leads to 41S leads to 36S+18S leads to 32S leads to 28S rRNA. The two pathways differ by the temporal sequence of endonuclease attack along the 41 S pre-rRNA chain. A minor fraction (mol.wt.2.9X10(6), 39S) is identified as most likely originating by a direct split of 28S rRNA from 45S pre-rRNA. These results show that in liver considerable flexibility exists in the order of cleavage of pre-rRNA molecules during processing.
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40
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Laval M, Bouteille M, Moulé Y. Effect of the ionic environment on the transcriptional activity of rat liver nucleoli. Exp Cell Res 1976; 102:365-75. [PMID: 976353 DOI: 10.1016/0014-4827(76)90052-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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41
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Ro-Choi TS, Raj NB, Pike LM, Busch H. Effects of alpha-amanitin, cycloheximide, and thioacetamide on low molecular weight nuclear RNA. Biochemistry 1976; 15:3823-8. [PMID: 182218 DOI: 10.1021/bi00662a027] [Citation(s) in RCA: 38] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Studies were made on the effects of alpha-amanitin, cycloheximide, and thioacetamide on synthesis and content of low molecular weight nuclear RNA. Cycloheximide, an inhibitor of protein synthesis and the synthesis of 45S pre-rRNA and 5S RNA, also inhibited synthesis of nuclear U1 and U3 RNAs. alpha-Amanitin, an inhibited the synthesis of U1 and U2 low molecular weight nuclear RNA. Thioacetamide, which induces nucleolar hypertrophy and increased nucleolar RNA polymerase activity, markedly increased synthesis of 5.8S RNA and U3 RNA. These results show that syntheses of individual low molecular weight nuclear (LMWN) RNAs are controlled by different regulatory mechanisms. In particular, there appears to be a specific relationship between U3 RNA and functional states of the nucleolus.
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42
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43
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Fong WF, Fuchs MS. The long term effect of α-amanitin on RNA synthesis in adult female Aedes aegypti. ACTA ACUST UNITED AC 1976. [DOI: 10.1016/0020-1790(76)90020-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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44
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Thonart P, Bechet J, Hilger F, Burny A. Thermosensitive mutations affecting ribonucleic acid polymerases in Saccharomyces cerevisiae. J Bacteriol 1976; 125:25-32. [PMID: 1107309 PMCID: PMC233331 DOI: 10.1128/jb.125.1.25-32.1976] [Citation(s) in RCA: 40] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Among 150 temperature-sensitive Saccharomyces cerevisiae mutants which we have isolated, 15 are specifically affected in ribonucleic acid (RNA) synthesis. Four of these mutants exhibit particularly drastic changes and were chosen for a more detailed study. In these four mutants, RNA synthesis is immediately blocked after a shift at the nonpermissive temperature (37 C), protein synthesis decays at a rate compatible with messenger RNA half-life, and deoxyribonucleic acid synthesis increases by about 40%. All the mutations display a recessive phenotype. The segregation of the four allelic pairs ts-/ts+ in diploids is mendelian, and the four mutants belong to three complementation groups. The elution patterns (diethylaminoethyl-Sephadex) of the three RNA polymerases of the mutants grown at 37 C for 3.5 h show very low residual activities. The in vitro thermodenaturation confirms the in vivo results; the half-lives of the mutant activities at 45 C are 10 times smaller than those of the wild-type enzymes. Polyacrylamide gel electrophoresis shows that the synthesis of all species of RNA is thermosensitive. The existence of three distinct genes, which are each indispensable for the activity of the three RNA polymerases in vivo as well as in vitro, strongly favors the hypothesis of three common subunits in the three RNA polymerases.
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45
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Mackedonski VV. Effect of the exotoxin of Bacillus thuringiensis on the biosynthesis and maturation of mouse liver nuclear RNA. BIOCHIMICA ET BIOPHYSICA ACTA 1975; 390:319-26. [PMID: 1125318 DOI: 10.1016/0005-2787(75)90352-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The effect of the exotoxin of Bacillus thuringiensis on the in vivo incorporation of [14-C] orotic acid into mouse liver nuclear rRNA and low molecular weight RNA was studied. The following results were obtained. 1. The exotoxin does not inhibit the synthesis of 45 S pre-rRNA, but causes a breakdown of these molecules. 2. The exotoxin inhibits the conversion of 38 S pre-rRNA into 32 S and 21 S. 3. The exotoxin inhibits the labelling of nuclear 5 S RNA, whereas the labelling of 4.6 S pre-tRNA is not affected. It is suggested that 5 S RNA may control the processing of 45 S pre-rRNA.
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46
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47
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Kedinger C, Simard R. The action of alpha-amanitin on RNA synthesis in Chinese hamster ovary cells. Ultrastructural and biochemical studies. J Cell Biol 1974; 63:831-42. [PMID: 4474178 PMCID: PMC2109362 DOI: 10.1083/jcb.63.3.831] [Citation(s) in RCA: 45] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
alpha-Amanitin acts in vitro as a selective inhibitor of the nucleoplasmic form B RNA polymerases. Treatment of Chinese hamster ovary (CHO) cells with this drug leads principally to a severe fragmentation of the nucleoli. While the ultrastructural lesions induced by alpha-amanitin in CHO cells and in rat or mouse liver are quite similar, the results diverge concerning the effect on RNA synthesis. It has been shown that in rat or mouse liver alpha-amanitin blocks both extranucleolar and nucleolar RNA synthesis. Our autoradiographic and biochemical evidence indicates that in CHO cells high molecular weight extranucleolar RNA synthesis (HnRNA) is blocked by the alpha-amanitin treatment, whereas nucleolar RNA (preribosomal RNA) synthesis remains unaffected even several hours after the inhibition of extranucleolar RNA synthesis. Furthermore, the processing of this RNA as well as its transport to the cytoplasm seem only slightly affected by the treatment. Finally, under these conditions, the synthesis of the low molecular RNA species (4-5S) still occurs, though less actively. The results are interpreted as evidence for a selective impairment of HnRNA synthesis by alpha-amanitin in CHO cells.
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48
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Hadjiolov AA, Milchev GI. Synthesis and maturation of ribosomal ribonucleic acids in isolated HeLa cell nuclei. A tracer study on the topology of the 45S precursor of ribosomal ribonucleic acids. Biochem J 1974; 142:263-72. [PMID: 4474879 PMCID: PMC1168276 DOI: 10.1042/bj1420263] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The synthesis and processing of RNA by isolated HeLa cell nuclei was studied at low ionic strength in the presence of alpha-amanitin. The RNA polymerase reaction, with endogenous template and enzyme, rapidly reaches a plateau dependent on the amount of nuclei. Evidence is presented that incorporation of [(3)H]UMP proceeds only in growing RNA chains, whereas initiation of new RNA chains is arrested. The product formed contains all the main components of the 45S pre-rRNA (precursor of rRNA) maturation pathway (45S, 32S and 20S pre-rRNA; 28S and 18S rRNA). Most of the labelled material is in the mature rRNA components and their immediate precursors, even at very short times of incubation (2min). Small, but definite, 5S and 4S RNA peaks are also observed. At shorter incubation times a substantial amount of [(3)H]UMP is incorporated into RNA molecules in the 24S and 10-16S zones. This RNA material is considered to represent the non-conserved segments of 45S pre-rRNA in the process of nucleolytic degradation. A model for the tracer study of the topology of 45S pre-rRNA, on arrest of rRNA initiation, is discussed. The experimental evidence obtained supports the following structure of 45S pre-rRNA: 5'-end-28S rRNA unit-18S rRNA unit-nonconserved segment-3'-end.
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