A ρ-recognition site on phage λ cro-gene mRNA

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Abstract
The synthesis of RNA catalysed by RNA polymerase from Escherichia coli is terminated at specific sites on DNA templates through the action of a multimeric basic protein known as ρ (refs 1, 2). Three lines of evidence suggest that an interactions of ρ with the nascent RNA is important for this termination. First, ρ binds strongly to RNA3; second, ρ expresses an RNA–dependent ATPase activity which is essential for termination4,5; third, RNA polymerase does not terminate RNA synthesis at ρ-dependent sites when the nascent RNA is digested by ribonuclease during transcription2,6. From the fact that certain RNAs, particularly single-stranded, pyrimidine-rich polymers containing at least 10% cytidylate residues, are more effective than other RNAs at promoting ρ-ATPase, it has been proposed7 that ρ recognises specific sites on a nascent RNA for its action. We present evidence here that ρ does bind at a specific region on a mRNA transcribed from bacteriophage λ DNA.