Release of Polarity in Escherichia coli by Gene N of Phage λ: Termination and Antitermination of Transcription

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Abstract
The induction of λ prophage provokes the constitutive expression of the adjacent gal operon in E. coli . This “escape synthesis” can result from transcription that initiates at a phage promoter and extends into the gal operon. The effect requires the product of the λ gene N. N -mediated transcription not only fails to terminate at the prophage-bacterial junction and at the ends of bacterial operons, but ignores termination signals caused by polar insertions or ochre mutations within gal . Suppression of polarity by N -function is a cis -effect; only transcription initiated at the phage promoter is influenced. We propose that the transcription complex is influenced by N -product to become termination-resistant at a site in the phage genome (juggernaut model). This site appears to be at or near the phage promoter.