The P2 phage old gene: sequence, transcription and translational control

Abstract The old ( o vercoming l ysogenization d efect) gene product of bacteriophage P2 kills Escherichia coli recB and recC mutants and interferes with phage λ growth [ Sironi et al., Virology 46 (1971) 387–396 ; Lindahl et al., Proc. Natl. Acad. Sci. USA 66 (1970) 587–594]. Specialized transducing λ phages, which lack the recombination region, can be selected by plating λ stocks on E. coli that carry the old gene on a prophage or plasmid [Finkel et al., Gene 46 (1986) 65–69]. Deletion and sequence analyses indicate that the old -encoded protein has an M r of 65 373 and that its transcription is leftward. Primer extension analyses locate the transcription start point near the right end of the virion DNA. A bacterial mutant, named pin 3 and able to suppress the effects of the old gene, has been isolated [Ghisotti et al., J. Virol. 48 (1983) 616–626]. In a pin 3 mutant strain, carrying the old gene on a prophage or plasmid, the amount of old transcript is greatly reduced. The effect of the pin 3 mutation is abolished by the wild-type allele of argU , an arginine tRNA that reads the rare Arg codons AGA and AGG, which are used for eight of the 14 Arg codons in the old gene. Thus the pin 3 allele probably stalls translation of the old mRNA, causing this mRNA to be degraded. Isoelectric focusing and electrophoretic analysis identify the old gene product as a basic protein of approx. 65 kDa.