Low molecular weight DNA polymerase of rat ascites hepatoma cells

Abstract

A low molecular weight DNA polymerase has been purified 2200-fold from rat ascites hepatoma cells. The polymerase is originally located in the nuclear membrane—chromatin fraction of the cell. The purified polymerase has no detectable exonuclease and endonuclease activities. The molecular weight of the enzyme was estimated to be 45 000 by gel-filtration method. The polymerase forms a complex with nicked DNA, but not with single stranded phage fd DNA. The polymerase has an alkaline pH optimum and requires Mn 2+ for maximum activity. The reaction was inhibited by salts, but the activity was rather stable for SH-reacting reagents. DNAase I-treated DNA is a good template for the reaction, but the digestion of DNAase I-treated DNA with exonuclease III showed no stimulating effect. Poly [d(A-T) · (T-A)] is more effective as template than DNAase I-treated DNA. The poly(dC) strand of poly [(dC) · (dG)] is well copied.