Effects of temperature changes on thymidine kinase in heat- and cold-sensitive cell-cycle mutants and 'wild-type' murine P-815 cells.
Two heat-sensitive (arrested in G1 at 39.5 degrees C) and two cold-sensitive (arrested in G1 at 33 degrees C) clonal cell-cycle mutants that had been isolated from the same clone (K 21), of the murine mastocytoma P-815 cell line, were tested for thymidine kinase (EC 2.7.1.21) activity. After shift of mutant cells to the nonpermissive temperature, thymidine kinase activity decreased, and minimal levels (i.e., less than 3% of those observed for 'wild-type' K 21 cells at the respective temperature) were attained within 16 h in heat-sensitive and after 3-4 days in cold-sensitive mutants, which is in good agreement with kinetics of accumulation of heat-sensitive and cold-sensitive cells in G1 phase. After return of arrested mutant cells to the permissive temperature, thymidine kinase of heat-sensitive cells increased rapidly and in parallel with entry of cells into the S phase. In cultures of cold-sensitive cells, however, initiation of DNA synthesis preceded the increase of thymidine kinase activity by approx. one cell-cycle time. Thymidine kinase activities in revertants of the heat-sensitive and cold-sensitive mutants were similar to those of 'wild-type' cells. In 'wild-type' K 21 cells incubated at 39.5 degrees C, thymidine kinase activity was approx. 30% of that at 33 degrees C. This difference is attributable, at least in part, to a higher rate of inactivation of the enzyme at 39.5 degrees C, as determined in cultures incubated with cycloheximide. The rapid increase of thymidine kinase activity that occurred after shift of K 21 cells and of arrested heat-sensitive mutant cells from 39.5 degrees C to 33 degrees C was inhibited by actinomycin D and cycloheximide.
D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D003080:Cold Temperature; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D006358:Hot Temperature; D007700:Kinetics; D012515:Mast-Cell Sarcoma / Q000201:enzymology / Q000235:genetics* / Q000503:physiopathology; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D013937:Thymidine Kinase / Q000235:genetics* / Q000378:metabolism
D003609:Dactinomycin; D003513:Cycloheximide; D013937:Thymidine Kinase