HeLa Cell R-Deoxyribonucleic Acid Polymerases

Abstract

Abstract R-DNA polymerase activity in HeLa cells is found in both the nuclear and cytoplasmic compartments. Extensive purification of the enzyme activity in the cytoplasm shows it to be separable into two distinct activities, I and II. Comparable purification of the nuclear R-DNA polymerase yields one main enzymatic activity which is apparently similar to cytoplasmic R-DNA polymerase II. R-DNA polymerase I copies poly(A) templates but not poly(C), poly(I), or poly(U) homopolymers, whereas Form II of the enzyme can copy all of the homopolymers. The two forms of the enzyme show different inhibition patterns in the presence of salt or ethanol. Both R-DNA polymerases are 110,000 daltons as measured by sedimentation studies and show Km values for deoxynucleoside triphosphates (approximately 5 x 10-7 m) that are one order of magnitude or more lower than the Km values of the DNA dependent-DNA polymerases of HeLa cells. Neither HeLa cell R-DNA polymerase I nor II is inhibited by antisera prepared against the reverse transcriptase obtained from either the Mason-Pfizer monkey virus, the Woolly monkey virus, or the Rauscher murine leukemia virus.