Purification and characterization of two forms of DNA polymerase .alpha. from HeLa cell nuclei

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Abstract
Isolated nuclei contained 2 active forms of DNA polymerase .alpha. (form I and form II). Form II was extracted from nuclei by KCl at concentrations lower than 0.18 M. Above 0.18 M selective extraction of form I was observed. The purified 2 active forms differed in chromatographic and electrophoretic behaviors, in their salt requirement for optimal activity, and in preference of template-primers, although both forms exhibited properties characteristic of DNA polymerase .alpha. such as sensitivity of N-ethylmaleimide, 1-.BETA.-D-arabinofuranosylcytosine triphosphate and aphidicolin. Marked difference between the 2 forms was preference of template-primer that form I was more active with poly(dT) .cntdot. (rA)10 than poly(dA) .cntdot. (dT)12 whereas form II exhibited higher activity with poly(dA) .cntdot. (dT)12 than poly(dT) .cntdot. (rA)10. Possible roles of 2 forms of DNA polymerase .alpha. in the processes of DNA replication will be discussed.

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