Inhibition of DNA Synthesis in Animal Cells by Ethylene Diamine Tetraacetate, and Its Reversal by Zinc

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During an investigation of the role of ions in growth regulation, it was found that ethylene diamine tetraacetate (EDTA) inhibits DNA synthesis about 10-fold in cultures of chick embryo cells, while ethylene glycol bis(β-amino ethyl ether)-N,N′-tetraacetate has no effect. RNA synthesis is only slightly inhibited by EDTA, and protein synthesis is unaffected. EDTA is inhibitory to DNA synthesis at a concentration much lower than that of either Ca++ or Mg++ present in the growth medium. The inhibition is prevented by the addition of Zn++ at a much lower concentration than that of the EDTA. Other metal ions are ineffective. The inhibition of DNA synthesis only becomes apparent after more than 6 hr of incubation with EDTA, and descends to its final level by 15 hr. Complete restoration of the original rate of DNA synthesis is achieved within 8-10 hr by the addition of Zn++. The low rate of DNA synthesis that occurs in a density-inhibited culture, is refractory to further inhibition by EDTA. Rous sarcoma cells are less sensitive to inhibition by EDTA than normal cells, but the sensitivity of both is increased by reducing the concentration of Ca++ in the medium. DNA synthesis in mouse 3T3 cells is also inhibited by EDTA. It is concluded that Zn++ is a continuing requirement for DNA synthesis in cultured vertebrate cells, and it is suggested that the availability of Zn++ within the cell may play a role in the regulation of cell multiplication.

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