Presence Of Emetine Research Articles

Nucleosome segregation at a defined mammalian chromosomal site.

When animal cells replicate chromatin under conditions precluding new histone biosynthesis, half of the daughter DNAs are devoid of nucleosomes and are sensitive to staphylococcal nuclease. DNA sequences resistant to nuclease are associated with preexisting nucleosomes, which redistribute to progeny DNA duplexes during replication. We labeled newly replicated DNA sequences in a simian virus 40 (SV40)-transformed Chinese hamster cell clone with 5-bromodeoxyuridine (BrdUrd) in the presence and absence of a protein biosynthesis inhibitor, emetine. We resolved single-stranded BrdUrd- and dT-DNA sequences protected from nuclease digestion by nucleosomes and determined from which strands of the integrated viral DNA parental template (dT) and newly replicated progeny (BrdUrd) sequences were derived. Because we knew that the cell clone studied contained all of its integrated SV40 DNA at a single chromosomal site, we were able to determine that preexisting nucleosomes segregated to only one of the two daughter duplexes containing the integrated viral sequence. Additionally, in the presence of emetine, the integrated viral origin of replication, ORIsv, appeared not to function as a chromosomal replication origin, perhaps reflecting the drug's effect on synthesis of SV40 large tumor antigen.

Stereochemistry of electroreductions of bromocyclopropanes: 1-asymmetric electrochemical synthesis by reduction at a mercury cathode in the presence of adsorbed alkaloïds

The electrochemical behaviours of 1-bromo-2,2-diphenylcyclopropane carboxylic acid, its methyl ester and 1,1-dibromo-2,2-diphenylcyclopropane are investigated in the presence of strongly adsorbed alkaloïds: yohimbine, emetine, brucine, strychnine and methylstrychninium cations. The polarographic study evidences the existence of interactions between the alkyl bromides and nitrogen cations; these interactions make easier the 2 e cleavage of the carbon-halogen bond. Whatever the alkaloïd used, rather poor optical yields are obtained after electroreduction of monobromo compounds. On the contrary, notably optically active products are obtained from the dibromide derivative, but only when the inductor can act as a protonating species; 45% optical yield can be achieved in the presence of emetine. The mechanism of asymmetric electrochemical synthesis is interpreted in terms of (i) preferential presentation of one of the two stereotopic faces of the substrate at the mercury cathode, made chiral by the adsorption of the alkaloïd and (ii) protonation by the acidic form of the inductor of the carbanion resulting from a 2 e reduction.

Phosphorylation of cleavage stage histone H1 in mitotic and prematurely condensed chromosomes

The cleavage stage variant of histone H1 (CS H1) in early sea urchin embryos is highly phosphorylated. As is the case for H1s from other cell types, CS H1 reaches its highest degree of phosphorylation during mitosis. Cs H1 from male chromosomes forced to prematurely condense and from mitotic chromosomes are phosphorylated to a similar extent. Despite the correlation between the degree of H1 phosphorylation and chromosome condensation, the two events can be separated. In the presence of emetine, a protein synthesis inhibitor, CS H1 is assembled onto the male pronuclear chromatin from a histone pool stored in the egg. Phosphorylation proceeds to a normal extent, but chromosome condensation is blocked. The data suggest that if the high degree of phosphorylation of H1 characteristic of mitotic chromosomes is required, it is not by itself sufficient, for chromosome condensation.

Program of early development in the mammal: Synthesis of mitochondrial proteins during oogenesis and early embryogenesis in the mouse

During oogenesis and early embryogenesis in the mouse, mitochondria of growing oocytes and cleaving embryos undergo extensive morphological alterations (e.g., L. Piko and D.G. Chase, 1973, J. Cell Biol. 58, 357; P.M. Wassarman and W. J. Josefowicz, 1978, J. Morphol. 156, 209). The experiments described here were carried out to determine whether or not proteins encoded by the mitochondrial genome are synthesized during these stages of development. Proteins synthesized by growing oocytes, fully grown oocytes, and eight-cell compacted embryos cultured in the presence or absence of emetine, an inhibitor of cytoplasmic protein synthesis, were examined by one- and two-dimensional gel electrophoresis. Electrophoretic patterns of [35S]methionine-labeled proteins in these cells were compared with each other, as well as with patterns of proteins synthesized in mouse follicle cells cultured in the presence or absence of emetine. In the presence of emetine, all of these cell types synthesize a very similar array of proteins and synthesis of these proteins is arrested by chloramphenicol, an inhibitor of mitochondrial protein synthesis. The molecular weights of the proteins synthesized in the presence of emetine are very similar to those of mitochondrial proteins synthesized in a variety of eukaryotic cells. Synthesis of mitochondrial proteins accounts for less than 2% of total protein synthesis in mouse oocytes, embryos, and follicle cells, such that they represent minor components in cells radiolabeled in the absence of emetine. Consequently, electrophoretic patterns of proteins radiolabeled in cells cultured in the presence of chloramphenicol are indistinguishable from those of cells cultured in the absence of the drug. On the other hand, electrophoretic patterns of preparations enriched in oocyte or follicle cell mitochondria show an enrichment of mitochondrial-encoded proteins. These results demonstrate that mitochondrial proteins are synthesized during oocyte growth and early embryogenesis in the mouse, despite the marked morphological alterations undergone by mitochondria during these same stages of development. In addition, these and other (L. Piko and D. G. Chase, 1973, J. Cell Biol. 58, 357) observations suggest that the mitochondrial transformations are under nucleocytoplasmic, rather than mitochondrial, control.

Polypeptide composition of Chlamydia trachomatis.

Strains of Chlamydia trachomatis representative of 14 serotypes were grown in HeLa 229 cells. HeLa cell susceptibility to chlamydial infection was increased by treating the host cells with DEAE-dextran. Optimal conditions of DEAE-dextran treatment were determined for each serotype of C. trachomatis to maximize chlamydial yields. Chlamydial polypeptides were selectively radiolabelled with 3H-labelled amino acids in the presence of emetine, an inhibitor of HeLa cell protein synthesis. The radiolabelled chlamydiae were purified from host cell components by density gradient centrifugation and their polypeptide composition was determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The distribution of the major chlamydial polypeptide of 38 000 to 42 000 daltons amongst the different serotypes correlated closely with the predominant human infections caused by each serotype. Lymphogranuloma venereum agents possessed a unique polypeptide of 118 000 daltons not found amongst trachoma inclusion conjunctivitis strains of chlamydiae. Chlamydial surface polypeptides were selectively radiolabelled with 125I by lactoperoxidase-catalysed oxidation. The major chlamydial polypeptide and polypeptides of 155 000 and 29 000 daltons were thus identified as surface polypeptides of the chlamydial elementary body. It is suggested that the 155 000 dalton polypeptide is a species-specific antigen, the major polypeptide is the principal outer membrane protein, and the 29 000 dalton polypeptide is the type-specific antigen.

Actin nascent chains are substrates for cyclic AMP-dependent phosphorylation in vivo.

Two-dimensional gel electrophoresis of extracts of S49 mouse lymphoma cells labeled with [35S]methionine in the presence of inducers or analogs of cyclic AMP reveals a protein that both affinity purification and peptide mapping show to be a form of nonmuscle actin. This actin species also exhibits cyclic AMP-dependent labeling with [32P]phosphate, and, after acid hydrolysis, 32P label is found associated with phosphoserine. Phosphorylated actin does not appear when cells prelabeled with [35S]methionine are treated with an inducer of cyclic AMP in the presence of emetine, an inhibitor of protein synthesis; this suggests that only the nascent form of actin is a substrate for cyclic AMP-dependent phosphorylation. As well as differing slightly in isoelectric points, beta and gamma actins are found to yield different partial proteolytic cleavage products with staphylococcal protease. This microheterogeneity in the major cellular actin component is repeated in both the metabolically labile delta/epsilon actin and phosphorylated actin, suggesting that these three forms of actin derive from the same two gene products.

Kinetics of the regeneration of sea-urchin cilia : II regeneration of animalized cilia

The kinetics of the regeneration of cilia of Arbacia punctulata animalized by treatment with trypsin have been examined. The cilia regenerate with biphasic kinetics: an initial linear phase which changes abruptly to a second, slower linear rate. Inhibition of protein synthesis with 10 microM emetine has little effect on the first phase but totally abolishes the second, suggesting that the first phase represents the utilization of a pre-existing precursor pool while the second reflects de novo protein synthesis. However, cilia will regenerate again following a second deciliation in the presence of emetine, to half the plateau value of the first regeneration, indicating that only a fraction of the pool of the limiting precursor can be assembled into the regenerating cilium. It is proposed that a residual pool of this precursor is required to maintain the assembly-disassembly equilibrium in favour of the assembled organelle.

Inhibition of cell-free protein synthesis by pppA 2′ p 5′ A 2′ p 5′ A: a novel oligonucleotide synthesized by interferon-treated L cell extracts

The oligonucleotide pppA 2′ p 5′ A 2′ p 5′ A is synthesized by extracts from interferon-treated mouse L cells in the presence of double-stranded RNA. This compound is a potent inhibitor of protein synthesis in cell-free systems prepared from L cells or rabbit reticulocytes. After an initial lag, rates of protein synthesis in vitro are severely depressed in the presence of the oligonucleotide, and polysomes become disaggregated. In the presence of high concentrations of emetine, an inhibitor of chain elongation, reticulocyte polysomes containing an average of 4–6 ribosomes per mRNA are partially degraded to structures containing 1–4 ribosomes after incubation with the oligonucleotide. The level of association of exogenous 35S-Met-tRNA f with initiation complexes is not decreased, and under some conditions is even increased, by the oligonucleotide. When RNA is extracted from control and inhibited reticulocyte lysates and assayed for active mRNA content by retranslation in a fresh mRNA-dependent system, the results show extensive loss of template activity in the material obtained from the incubations containing pppA 2′ p 5′ A 2′ p 5′ A. The data are consistent with a mechanism in which this inhibitor activates a nuclease which prevents mRNA from being utilized for protein synthesis. This mechanism is contrasted with that of the heme-controlled repressor, another potent inhibitor of translation, which causes extensive inhibition of Met-tRNA f binding to initiation complexes, has no effect on polysome size in the presence of emetine and does not inactivate mRNA.

Metabolic properties of the products of mitochondrial protein synthesis in HeLa cells.

The metabolic behavior of the mitochondrial protein synthesis products has been investigated in HeLa cells. Particular attention was given to the four major electrophoretic components (designated as Nos. 2, 3, 5, and 8) of the 10 previously identified as organelle-specific products. Inhibition of cytoplasmic protein synthesis with emetine or cycloheximide causes a rapid decline in the rate of mitochondrial protein synthesis, with an estimated half-life of 1 to 2 h, affecting in a parallel way all the discrete components. About 30% of the original synthetic activity appears to be resistant to emetine treatment for at least 24 h; however, all the polypeptides synthesized after the first 4 h of cell exposure to emetine are metabolically unstable, possibly because of lack of integration into the inner mitochondrial membrane. An analysis of the stability of newly synthesized products of mitochondrial protein synthesis pulse-labeled in the presence of cycloheximide and then chased in the absence of the drug (i.e. under conditions of resumed cytoplasmic protein synthesis) has revealed marked differences among the various discrete components. In particular, about three-fourths of the radioactivity associated with components 3 and 5 decays within 4 h of chase, the remainder being substantailly stable afterwards; by contrast, the radioactivity in components 2 and 8 shows only a slow decline during a 3-day chase. If the chase is carried out under conditions of a persistent block of cytoplasmic protein synthesis, as is the situation after a pulse labeling in the presence of emetine, all newly synthesized components appear to be destablized in various degrees, with the exception of component 5, which is to a great extent stabilized. Inhibition of mitochondrial protein synthesis with chloramphenicol has a progressive stabilizing effect on most of the discrete components newly synthesized after removal of the drug; this effect is especially striking in the case of component 5 which, in experiments of continuous labeling in the presence of emetine after prolonged chloramphenicol treatment, becomes, after 24 h of labeling or more, the only recognizable peak in the electrophoretic pattern of the sodium dodecyl sulfate-lysed mitochondrial fraction. The results of the kinetic experiments described here are interpreted in terms of two roles of cytoplasmically synthesized proteins, one required for the synthesis of polypeptides within the organelles, the other necessary for the stabilization of the mitochondrial products.

Hormonal control of reinitiation of meiosis in starfish: The requirement of 1-methyladenine during nuclear maturation

The dependence of meiosis reinitiation on the continuous supply of the hormonal effector 1-methyladenine (1-MA) was studied on Marthasterias glacialis starfish oocytes by eliminating this compound from the medium at various time intervals after its application. It has been shown that the presence of 1-MA in the medium is required only during a very short period (4 min 30 sec under our experimental conditions). After this period, the cellular process of nuclear maturation is triggered and continues without any further exogeneous supply of 1-MA. The effect of various inhibitors of RNA and protein synthesis on 1-MA induced germinal vesicle breakdown was studied in experiments where the supply of the inhibitors was restricted either to the hormone-dependent or to the hormone-independent period. The results demonstrate that 1-MA control of germinal vesicle breakdown does not involve any compulsory protein synthesis, as indicated by the time course of labeled amino-acid incorporation into hot TCA insoluble fractions in the presence of emetine, cycloheximide or puromycin. Moreover, it is strongly suggested that transcription is not required for this hormonal control. On the other hand, high concentrations of emetine, cycloheximide and puromycin can inhibit both 1-MA influx through the oocyte membrane and germinal vesicle breakdown when they are applied during the hormone-dependent phase. However, various evidence shows that these effects are independent phenomena. Data are presented which support the view that these compounds might act either by inhibiting the binding of 1-MA with its membrane receptors or by modifying membrane properties so that the pattern of events elicited by 1-MA stimulation do not occur.

Identification of discrete electrophoretic components among the products of mitochondrial protein synthesis in HeLa cells.

Abstract Proteins synthesized in vivo by HeLa cell mitochondria in the presence of emetine, an inhibitor of cytoplasmic protein synthesis, have been characterized as to their electrophoretic mobility, solubility properties in organic solvents, and kinetics of labeling with [3H]isoleucine. Ten distinct electrophoretic components in the molecular weight range from about 11,000 to 42,000 have been identified with high reproducibility among the products of mitochondrial protein synthesis. Control experiments involving direct sodium dodecyl sulfate lysis of whole cells, or the use of the protease inhibitor phenylmethylsulfonylfluoride during cell homogenization and fractionation, have excluded a significant role of enzymic degradation during extraction in producing the observed electrophoretic pattern of mitochondrial protein products. A selective solubilization of mitochondrial protein products, representing a 20 to 30-fold purification with respect to the cytoplasmically synthesized proteins, has been obtained by using a neutral chloroform/methanol mixture. At least six of the electrophoretic components with a molecular weight greater than 20,000 were found to be extracted to an appreciable extent with neutral chloroform/methanol. A fairly co-ordinate labeling of the discrete electrophoretic components has been observed during a one-hour exposure period of the cells to [3H]isoleucine in the presence of emetine, without any clear evidence of intorconversion.

Regulation of Pyruvate Kinase from the Hepatopancreas of the Crab Carcinus maenas

Conference Article| June 01 1975 Regulation of Pyruvate Kinase from the Hepatopancreas of the Crab Carcinus maenas IAN G. GILES; IAN G. GILES 1Department of Physiology and Biochemistry, University of Southampton, Southampton SO9 5NH, U.K. Search for other works by this author on: This Site PubMed Google Scholar PETER C. POAT; PETER C. POAT 1Department of Physiology and Biochemistry, University of Southampton, Southampton SO9 5NH, U.K. Search for other works by this author on: This Site PubMed Google Scholar KENNETH A. MUNDAY KENNETH A. MUNDAY 1Department of Physiology and Biochemistry, University of Southampton, Southampton SO9 5NH, U.K. Search for other works by this author on: This Site PubMed Google Scholar Biochem Soc Trans (1975) 3 (3): 400–402. https://doi.org/10.1042/bst0030400 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Cite Icon Cite Get Permissions Citation IAN G. GILES, PETER C. POAT, KENNETH A. MUNDAY; Regulation of Pyruvate Kinase from the Hepatopancreas of the Crab Carcinus maenas. Biochem Soc Trans 1 June 1975; 3 (3): 400–402. doi: https://doi.org/10.1042/bst0030400 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Society Transactions Search Advanced Search This content is only available as a PDF. © 1975 Biochemical Society1975 Article PDF first page preview Close Modal You do not currently have access to this content.

Inhibition of excystment of Schizopyrenus russelli cysts in the presence of emetine and its cysticidal effect in conjunction with sodium lauryl sulphate.

SUMMARY: Excystment agents (extract of Escherichia coli, living E. coli and glutamic acid) failed to cause excystment of Schizopyrenus russelli cysts in the presence of either emetine or compounds I and II (structurally based on emetine). A very high percentage of the cysts excysted in the presence of the excystment agents after the removal of emetine, showing that the treated cysts were viable. Ninhydrin reaction, using a fixed amount of glutamic acid and increasing concentrations of emetine, showed progressive inhibition of colour development. This suggests the possible binding of excystment factor to emetine, thus preventing excystment. Excystment inducing property of the excystment agents could not be prevented in the presence of carbarsone. When the cysts were treated with sodium lauryl sulphate and then with emetine or with sodium lauryl sulphate and emetine together, there was hardly any excystment. Sodium lauryl sulphate rendered the cyst wall permeable to emetine and the latter killed the cysts.