Induction of G1- cells at high frequency.

Abstract

Experimental conditions are reported on the induction of G1- cells at high frequency by ultraviolet irradiation of temperature-sensitive cells arrested in G1 phase at the restricted temperature. Neither the wild type cells of Balb/C-3T3 nor the temperature-sensitive derivative of tsA83 grown at the permissive temperature could be 'mutated' under similar conditions. One such 'mutant' (RI8) was 'inducible' from a G1+ phenotype at 33 degrees C to G1- state at 38 degrees C within one cell generation time. The 'inducible' property of RI8 from G1+ to G1- lends support to the theory that the duration of the G1+ phenotype is determined by the level of precursors for DNA synthesis. Since the G1- variants were isolated from revertants, the frequency of 'mutagenesis' appeared to be artifically high.