Regenerating rat liver DNA polymerases: disimilitude or relationship between nuclear and cytoplasmic enzymes?

The possible relationship between the nuclear and cytoplasmic DNA polymerases of regenerating rat liver was studied by sucrose gradient analysis, salt dissociation, and with specific inhibitors. After aqueous subcellular fractionation and removal of the nuclear membranes, three species of DNA-dependent DNA polymerases were characterized: 1) a DNA polymerase-beta in the nuclei. 2) a DNA polymerase-alpha in the cytosol which was not dissociated at high salt concentrations; and 3) an intermediate form in the cytosol and in the Triton wash containing the nuclear membranes. The latter form behaved like DNA polymerase-alpha et low salt concentration but was dissociated at high salt concentrations to a low molecular weight species with properties like DNA polymerase-beta (resistance to inhibition by N-ethylmaleimide, heparin and KCL). In vitro reassociation experiments suggest that this intermediate form corresponds to the association of DNA polymerase-beta with a membrane component or cytoplasmic protein(s) which appear(s) in regenerating rat liver.