C. Mathews
Apr 1, 1975
Citations
1
Influential Citations
45
Citations
Quality indicators
Journal
Experimental cell research
Abstract
Abstract Pools of deoxyribonucleoside 5′ triphosphates were measured in eggs of the sea urchin, Strongylocentrotus purpuratus , both before and early after fertilization. The pools in unfertilized eggs are very large, amounting to between one and seven diploid nuclear equivalent units/egg. These high levels are maintained, with some fluctuations, for more than 2 h after fertilization, even in the presence of inhibitors of deoxynucleotide synthesis. This points to the existence of a large reservoir of dNTP precursors in the egg, as had been inferred from earlier studies. Exogenous radiolabeled DNA precursors, notably 3 H-thymidine, are routinely used to monitor DNA synthesis in sea urchins and other organisms. Because of the giant endogenous precursor pools and their fluctuations, plus previously described changes in deoxynucleoside transport and phosphorylation after fertilization, the relationship between thymidine labeling and DNA synthesis requires clarification. At high thymidine concentrations, as shown herein, nearly all of the DNA thymine residues appear to be derived from exogenous thymidine during the first S phase. The mechanism of this preferential utilization is not known.