DNA synthesis in mammalian nuclei: Inhibition of DNA synthesis in the resting rat liver nucleus by ethidium bromide, proflavin and actinomycin D

The DNA polymerase of resting rat liver nuclei has been used to study the mode of inhibition of DNA synthesis by ethidium bromide, proflavin and actinomycin D. The DNA polymerase is reversibly inhibited by all three substances and all three substances appear to have the same general mode of action. The inhibitors seem to have only a small effect on the activity of the enzyme when there is an excess of suitable DNA priming sites but have a relatively larger effect when priming sites are limited. The possibility that inhibition of nucleases might be responsible for the lack of primer sites or the failure to "path-clear" at the primer sites has been investigated.