[Bacteriophage MS2 mutants with disrupted phage replicase repressor activity].

A number of ts-mutants with altered characteristics of RNA synthesis in non-suppressor cells at elevated temperatures have been obtained after HNO2-treatment of phage MS2am623 (amber mutation in site 50). The mutant ts130 is studied in detail: its peak of RNA synthesis is displaced 10 min. later and the total amount of RNA is reduced in 5-10 times. No RNA synthesis is observed in ts130-infected cell at 46 degrees C. Changes in the character of RNA synthesis are accompanied by the over-production of phage subunit of replicase: at 42 degrees C the replicase/RNA ratio in ts130 is 20 times higher than that of the original phage MS2am623. It is assumed that there is a decrease in the activity of replicase--RNA repressor complex in ts130 resulting in the loss of replicase control over its own synthesis while the control of coat protein synthesis remains unaffected.