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Studies of Temperature Sensitive Mutants of Bacteriophage Qβ, Defective in both Replication and Translation
Abstract
Summary
Temperature sensitive mutants of bacteriophage Qβ have been isolated which fail in the synthesis of their virus RNA at the non-permissive temperature (42 °C). Nine mutants have been studied in some detail. Cells infected with these mutants at 37 °C and incubated long enough to produce substantial amounts of Qβ RNA cease Qβ RNA replication when shifted to 42 °C. The mutants can be classified into 3 groups according to the amount of Qβ RNA replicase activity exhibited in extracts from infected cells isolated at various times after shift to 42 °C: in group 1 mutants, enzyme activity is the same, regardless of the time of isolation after shift; in group 2 mutants enzyme activity increases with time of isolation after shift; in group 3 mutants, enzyme activity decreases with time of isolation after shift. Synthesis of all virus proteins is suppressed at 42 °C in cells infected with group 1 or group 3 mutants. In cells infected with group 2 mutants, synthesis of Qβ RNA replicase subunit β is increased, but synthesis of other virus proteins is depressed at 42 °C. The inhibition of virus RNA and protein synthesis is reversible. A detailed analysis of these experiments suggests that a defective Qβ RNA replicase is involved in the inhibition of both virus RNA and protein synthesis.
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© Journal of General Virology 1975