Abstract
Rapid decay of DNA replicating activity was observed when cells were incubated initially for a brief period in isotonic sucrose solution with 2-mercaptoethanol before the assay of [3H]TTP incorporation. This rapid decay was prevented when ATP was added or when 2-mercaptoethanol was omitted from the solution during the incubation. Furthermore, 2-mercapto-ethanol inhibited the incorporation of [3H]TTP into the DNA of the per-meabilized cells although the initial rate of incorporation of [3H]TTP was the same as for the control. Since DNA polymerase activity was not inhibited by 2-mercaptoethanol, our results suggest that the DNA replication complex in mouse cells contains some unknown factors that are destabilized by 2-mer-captoethanol, but the activity of the complex is protected by ATP.
