Increased uptake of thymidine in the activation of sea urchin eggs. III. Effects of aphidicolin

✍ Scribed by David Nishioka; Christopher E. Killian; Cecilia T. Chacon; Magdalene K. Sgagias

• Publisher: John Wiley and Sons
• Year: 1984
• Tongue: English
• Weight: 839 KB
• Volume: 118
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041180107

✦ Synopsis

Uptake and phosphorylation of externally supplied [3H]-thymidine are fully stimulated in fertilized sea urchin eggs exposed to 5.0 pg/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 t h e transported thymidine is immediately phosphorylated to the triphosphate. The intracellular levels of 13H]-thymidine triphosphate (3H-dlTP) resulting from an external supply of [3H]-thymidine is therefore equal in aphidicolintreated 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 aphidi-Colin. The full availability of 3H-dlTP 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 pg/ml. In the continuous presence of 5.0 &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.