Changes in RNA polymerase II in a cell cycle-specific temperature-sensitive mutant of hamster cells

tsAF8 cells are a temperature-sensitive mutant of BHK cells that arrest at the nonpermissive temperature in the G1 phase of the cell cycle. The activity of solubilized RNA polymerase II and its ability to bine [3H]-gamma-amanitin decrease in tsAF8 cells at 40.6 degrees, with a half-life of approximately 10 hr. No appreciable changes occur in these two parameters in tsAF8 cells at 34 degrees or in BHK cells at either 34 degrees or 40.6 degrees. Protein synthesis is not appreciably affected for at least 24 hr after tsAF8 cells are shifted to 40.6 degrees. These results indicate that in tsAF8 cells at the nonpermissive temperature, there is a defect in either the synthesis, the assembly, or the stability of RNA polymerase II, and that the loss of RNA polymerase II molecules is not due to widespread cellular damage.