The relationship between two murine DNA-dependent DNA polymerases from the cytosol and the low molecular weight DNA polymerase

Abstract

After aqueous subcellular fractionation and partial purification by phosphocellulose chromatography, murine cells are found to contain a low molecular weight DNA-dependent DNA polymerase (β) in the nuclear fraction and two distinguishable DNA-dependent DNA polymerases (C-I and C-II) in the cytosol. Both C-I and C-II are found in testis, liver, and regenerating liver; the amount of C-I being several fold increased in the regenerating liver and in immature testis. C-I and C-II are distinguishable by the criteria of salt sensitivity, inhibition by single-stranded DNA, elution from phosphocellulose, inhibition by 0.3 mM N-ethylmaleimide, template preference, and sedimentation coefficient. C-II is dissociated by 0.25 M KCl to an active form of DNA polymerase of sedimentation coefficient 3.5 S while C-I is not dissociated, maintaining its sedimentation coefficient of 7.2 S. Many similar chemical and physical properties of C-II and the low molecular weight nuclear DNA polymerase (β) suggest that C-II may represent an aggregate state of β monomers. The size, reaction properties and the increase in enzyme activity under conditions of rapid cellular proliferation suggest C-I is analogous to the α DNA polymerase.