Characterization of a temperature-sensitive mutant of mouse FM3A cells defective in DNA replication.

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Abstract
The characterization of a temperature-sensitive mutant (tsFT20 strain, dnats) of mouse FM3A cells is reported. After incubation of tsFT20 cells at the nonpermissive temperature (39.degree. C), DNA synthesis ceased with little change in either RNA or protein synthesis. Flow-microfluorometric analysis revealed that the cell cycle of tsFT20 cells grown at 39.degree. C for 16 h was similar to that of wild-type cells that were synchronized at the G1/S boundary and at S phase by treatment with aphidicolin, a specific inhibitor of DNA polymerase .alpha.. The DNA polymerase .alpha. activity of tsFT20 cells measured in crude cell extracts or in purified preparations was inactivated more rapidly at 39.degree. C than the activity of wild-type cells. In the growth revertants of the tsFT20 cell strain, the heat lability of DNA polymerase .alpha. decreased. tsFT20 is a temperature-sensitive mutant of DNA polymerase .alpha. or of a factor associated with DNA polymerase .alpha. that is essential for its activity.

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