DNA polymerase and thymidine kinase activities in MC-29 virus-induced transplantable hepatoma and the effect of cytostatic treatment of these activities.
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.
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D009189:Avian Myeloblastosis Virus; D003520:Cyclophosphamide / Q000494:pharmacology; D003561:Cytarabine / Q000494:pharmacology; D004256:DNA Polymerase I / Q000378:metabolism; D004257:DNA Polymerase II / Q000378:metabolism; D004258:DNA Polymerase III / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D003673:Defective Viruses; D005472:Fluorouracil / Q000494:pharmacology; D008099:Liver / Q000201:enzymology; D008114:Liver Neoplasms, Experimental / Q000201:enzymology* / Q000209:etiology; D051381:Rats; D013379:Substrate Specificity; D013937:Thymidine Kinase / Q000378:metabolism*
D000970:Antineoplastic Agents; D003561:Cytarabine; D003520:Cyclophosphamide; D013937:Thymidine Kinase; D004256:DNA Polymerase I; D004257:DNA Polymerase II; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase; D005472:Fluorouracil