Increased uptake of thymidine in the activation of sea urchin eggs. III. Effects of aphidicolin.
Uptake and phosphorylation of externally supplied [3H]-thymidine are fully stimulated in fertilized sea urchin eggs exposed to 5.0 micrograms/ml aphidicolin. As in untreated controls, the rate of uptake in aphidicolin-treated eggs increases greater than 50-fold shortly after fertilization, and greater than 85% of the transported thymidine is immediately phosphorylated to the triphosphate. The intracellular levels of [3H]-thymidine triphosphate (3H-dTTP) resulting from an external supply of [3H]-thymidine is therefore equal in aphidicolin-treated and untreated fertilized eggs. Under the same experimental conditions, the incorporation of externally supplied [3H]-thymidine into newly synthesized DNA of fertilized eggs is 90% inhibited by exposure to aphidicolin. The full availability of 3H-dTTP in these eggs further suggests that aphidicolin inhibits specifically at the level of DNA synthesis. This inhibitory effect is proportional to the concentration of aphidicolin between 0 and 5.0 micrograms/ml. In the continuous presence of 5.0 micrograms/ml aphidicolin, fertilized eggs fail to undergo mitotic chromosome condensation, nuclear envelope breakdown, and cytokinesis, suggesting a dependent link between these processes and the completion of nuclear DNA synthesis.
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D016590:Aphidicolin; D004247:DNA / Q000096:biosynthesis; D004224:Diterpenes / Q000494:pharmacology*; D005260:Female; D010766:Phosphorylation; D012617:Sea Urchins; D013936:Thymidine / Q000378:metabolism*; D014316:Tritium; D015053:Zygote / Q000187:drug effects / Q000378:metabolism*
D000903:Antibiotics, Antineoplastic; D004224:Diterpenes; D014316:Tritium; D016590:Aphidicolin; D004247:DNA; D013936:Thymidine