DNA Polymerase and Thymidine Kinase Activities in MC-29 Virus-Induced Transplantable Hepatoma and the Effect of Cytostatic Treatment of These Activities

Chem Biol Interact. 1982 Aug;41(2):181-92. doi: 10.1016/0009-2797(82)90088-6.

Abstract

The activity of DNA polymerases and thymidine kinase was compared in the MC-29 leukosis virus-induced transplantable hepatoma and in the livers of rats treated with cyclophosphamide (CP), cytosine-arabinoside (ara-C) and 5-fluoro-uracil (5-FU). The specific activity of DNA polymerase was twenty times greater in the MC-29 leukosis virus-induced hepatoma, while thymidine kinase was only 3-5 times greater than in liver. All three enzymes showed Michaelis-Menten kinetics in their substrate and template saturation curves. The template utilization of DNA polymerases from hepatoma and from liver was compared. Both had higher activities on a poly(dA) . poly(dT) template at pH 8.0, than on DNA at pH 7.5. After chromatography on a phosphocellulose column two polymerases were separated. The first peak eluted by 0.15 m KCl preferred DNA as template (polymerase alpha). The second eluted by 0.5 M KCl worked better on poly(dA) . poly(dT) (polymerase beta). Thymidine kinase was eluted by 0.25 m KCl. Inhibition by N-ethylmaleimide (NEM) showed the polymerase alpha to be sensitive and the polymerase beta to be resistant to the sulfhydryl blocking agent; similar to the respective enzymes of other eukaryotic cells. The specific activity of DNA polymerase decreased after CP treatment at 6 h and 72 h and after ara-C treatment at 72 h. The specific activities of thymidine kinase were not changed significantly in response to the drug administrations.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacology*
  • Avian Myeloblastosis Virus
  • Cyclophosphamide / pharmacology
  • Cytarabine / pharmacology
  • DNA Polymerase I / metabolism
  • DNA Polymerase II / metabolism
  • DNA Polymerase III / metabolism
  • DNA-Directed DNA Polymerase / metabolism*
  • Defective Viruses
  • Fluorouracil / pharmacology
  • Liver / enzymology
  • Liver Neoplasms, Experimental / enzymology*
  • Liver Neoplasms, Experimental / etiology
  • Rats
  • Substrate Specificity
  • Thymidine Kinase / metabolism*

Substances

  • Antineoplastic Agents
  • Cytarabine
  • Cyclophosphamide
  • Thymidine Kinase
  • DNA Polymerase I
  • DNA Polymerase II
  • DNA Polymerase III
  • DNA-Directed DNA Polymerase
  • Fluorouracil