Dependence of Periodic Dna Synthesis on Protein Synthesis: Delay of Dna Synthesis in the Early Cleavage Stage of Sea Urchin Embryos Treated With Cycloheximide and Colchicine

Suzuki, Norio; Mano, Yoshitake

doi:10.1111/j.1440-169x.1973.00113.x

Cited by 11 publications

(1 citation statement)

References 24 publications

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“…Under the expremental conditions, a slight delay in cell division as well as in the cell cycle of DNA synthesis was observed. These observations are inconsistent with the dependency of DNA synthesis on protein synthesis (39). Fig.3.…”

Section: Resultscontrasting

confidence: 55%

Nature of the Inhibition of Protein Synthesis by Ethionine and Amino Acid Uptake in Early Sea Urchin Embryos

1977

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The inhibition of protein synthesis by ethionine reported previously was found to be apparent, and ethionine inhibited only amino acid uptake like other usual amino acids. Even under such strong inhibition of the uptake, the syntheses of protein and DNA remained almost undiminished. The uptake of amino acid mixture by sea urchin embryos in the early cleavage stage was found to be carried out by active transport, since it was temperature-sensitive and was inhibited by 2,4-dinitrophenol. The uptake of an amino acid mixture or of single amino acids, e.g., valine, leucine and phenylalanine, was inhibited nonspecifically by an excess amount of other single amino acids added exogenously. Reflecting the inhibition of amino acid uptake, in vivo incorporation of amino acids into the protein fraction was apparently inhibited by excess amounts of other amino acids. As far as tested, the inhibition seems to be nonspecific and competitive for all amino acid species. The uptakes of leucine and phenylalanine were inhibited mutually by competition, with almost the same Km and Ki.In a previous paper (32), it was reported that lo-' M DL-ethionine almost completely inhibited in vivo protein synthesis by sea urchin embryos. A peculiar phenomenon, however, was then encountered: cell division was found to proceed almost normally under the strong inhibition of incorporation of exogenously added amino acids. Ethionine has been known to inhibit protein synthesis by degrading the polysomes ( 1 2 , 4 1-43) or causing the appearance of abnormal ribosomes (3), and also to interfere with the syntheses of DNA (24, 36) and RNA (3,37, 38, 43). Recent investigation has also demonstrated that ethionine inhibits the in vivo syntheses of these macromolecules in sea urchin embryos (14). If all of these observations are valid, one might conclude that the chemical processes for cell division in early development do not require protein synthesis, which is explicitly inconsistent with the present common knowledge.The present study was carried out to attempt to resolve these conflicts. The results indicate that the apparent inhibition of protein synthesis by ethionine is due to the inhibition of amino acid uptake by the presence of an excess amount of other amino acids, and represents a general case of competitive inhibition. MATERIALS AND METHODSMature eggs of the sea urchins, Hemicentrotus pulcherrimus, Anthocidaris crassispina and Pseudocentrotus depressus, were used. No detectable difference was found among these species. Fertilization was effected by

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Section: Resultscontrasting

confidence: 55%

Nature of the Inhibition of Protein Synthesis by Ethionine and Amino Acid Uptake in Early Sea Urchin Embryos

1977

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The role of spindle microtubules in the timing of the cell cycle in echinoderm eggs

Sluder¹,

Miller²,

Spanjian³

1986

J. Exp. Zool.

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Spindle microtubules play an important role in the mechanisms that control the timing of cell cycle events in the eggs of the sea urchins L. variegatus and L. pictus. However, recent work which used colchicine to block microtubule assembly in the eggs of two other echinoderms, S. purpuratus and D. excentricus, has raised serious questions about the generality of this role for spindle microtubules. Thus, we have systematically examined the role of spindle microtubules in the timing of the cell cycle in the fertilized eggs of these latter species. We treated eggs of both species with 5-10 microM Colcemid for several minutes starting 30 min after fertilization to completely prevent spindle microtubule assembly for several h. We used Colcemid, instead of colchicine, because it is effective at lower doses and, at these doses, shows no detectable toxic side effects. We compared for control and treated eggs the time course of nuclear envelope breakdown/reformation and DNA synthesis. We found for both species that the eggs continue to cycle without spindle microtubules; mitosis is up to twice the normal duration while interphase remains essentially unaffected. To test for the possible toxic side effects of the 1-2 mM colchicine used earlier on S. purpuratus and D. excentricus, we treated eggs of these two species, and also those of L. variegatus, with 1 mM lumi-colchicine. This photo-inactivated form of colchicine, which does not bind to tubulin, substantially prolongs mitosis and, to a lesser extent, interphase. Thus, the results of the earlier work are most easily explained by the combination of specific and nonspecific effects of the 1-2 mM colchicine used. Our present results indicate that the importance of spindle microtubules in the mechanisms that control the timing of the mitosis portion of the cell cycle is a general phenomenon.

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Rhythms of Protein Synthesis and Other Circahoralian Oscillations: The Possible Involvement of Fractals

Brodsky¹

1992

Ultradian Rhythms in Life Processes

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Dependence of Periodic Dna Synthesis on Protein Synthesis: Delay of Dna Synthesis in the Early Cleavage Stage of Sea Urchin Embryos Treated With Cycloheximide and Colchicine

Cited by 11 publications

References 24 publications

Nature of the Inhibition of Protein Synthesis by Ethionine and Amino Acid Uptake in Early Sea Urchin Embryos

Nature of the Inhibition of Protein Synthesis by Ethionine and Amino Acid Uptake in Early Sea Urchin Embryos

The role of spindle microtubules in the timing of the cell cycle in echinoderm eggs

Rhythms of Protein Synthesis and Other Circahoralian Oscillations: The Possible Involvement of Fractals

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