Studies of DNA polymerases alpha and beta from cultured human cells in various replicative states

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Abstract
DNA polymerase activities from HeLa cells and from cultured diploid human fibroblasts in various growth states were compared. α-Polymerase activities from log phase fibroblasts treated with sodium butyrate and from stationary phase HeLa cells had DEAE-cellulose elution patterns that differed from those of polymerases from dividing cells. Moreover, α- and β-polymerases from nondividing cells replicated synthetic polymers less faithfully. Although similar changes were observed previously for polymerases from late-passage and postconfluent early passage fibroblasts, amounts of α-polymerase activity recovered from nondividing cells in this study did not dramatically decline as they had in the former cases. The α-polymerase activities from HeLa cells and fibroblasts in various growth states sedimented near 7.5S in 0.4 M KCl and could be inhibited by a monoclonal lgG fraction prepared against KB cell α-polymerase. By several criteria, there was no significant differences in levels of UV-stimulated repair synthesis observed in early or late-passage postconfluent fibroblasts or in log phase fibroblasts treated with sodium butyrate. In summary, levels of α-polymerase do not necessarily correlate either with replicative activity or with apparent levels of repair synthesis. However, cells with decreased replicative activity always yielded enzyme with decreased fidelity in vitro and altered chromatographic behavior. It appears, therefore, that the alterations observed for α-polymerase from late-passage cells may be attributed more generally to the nondividing nature of these cells.

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