Effects of lead acetate on DNA and RNA synthesis by intact HeLa cells, isolated nuclei and purified polymerases

Abstract

The effects of lead acetate on DNA and RNA synthesis have been investigated with intact HeLa cells, isolated nuclei, and purified DNA and RNA polymerases. No inhibition of DNA or RNA synthesis in intact cells was found even after exposure to 0.5 mM lead acetate for 18 hr. In contrast, both DNA and RNA synthesis in isolated nuclei were inhibited by lead (with 50% inhibition at approximately 150 and 80 μM respectively). Similarly, both HeLa DNA polymerase α and RNA polymerase II were inhibited, with 50% inhibition obtained at approximately 150 and 20 μM lead acetate respectively. The inhibition of nucleic acid synthesis in isolated nuclei can thus be accounted for by inhibition of the polymerases. The sensitivity of Escherichia coli DNA polymerase I to lead acetate was found to be significantly greater than the HeLa DNA polymerase α(50% inhibition at only 10 μm), but the sensitivity of the E. coli RNA polymerase was the same as that of the HeLa enzyme.