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The optional E. coli prr locus encodes a latent form of phage T4-induced anticodon nuclease
R Levitz1, D Chapman, M Amitsur
1Department of Biochemistry, Tel Aviv University, Ramat Aviv, Israel.
Abstract:
The optional Escherichia coli prr locus restricts phage T4 mutants lacking polynucleotide kinase or RNA ligase. Underlying this restriction is the specific manifestation of the T4-induced anticodon nuclease, an enzyme which triggers the cleavage-ligation of the host tRNALys. We report here the molecular cloning, nucleotide sequence and mutational analysis of prr-associated DNA. The results indicate that prr encodes a latent form of anticodon nuclease consisting of a core enzyme and cognate masking agents. They suggest that the T4-encoded factors of anticodon nuclease counteract the prr-encoded masking agents, thus activating the latent enzyme. The encoding of a tRNA cleavage-ligation pathway by two separate genetic systems which cohabitate E. coli may provide a clue to the evolution of RNA splicing mechanisms mediated by proteins.
Insights
The Escherichia coli prr locus restricts phage T4 by activating a latent anticodon nuclease. This enzyme cleaves and ligates host tRNALys, revealing insights into RNA splicing evolution.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The Escherichia coli prr locus influences phage T4 replication, particularly mutants deficient in polynucleotide kinase or RNA ligase.
- Phage T4 infection induces anticodon nuclease activity, which targets host transfer RNA (tRNA) for cleavage and ligation.
Purpose of the Study:
- To investigate the molecular basis of the prr locus's restriction of phage T4.
- To elucidate the mechanism of T4-induced anticodon nuclease activation and its interaction with the prr locus.
Main Methods:
- Molecular cloning of prr-associated DNA.
- Nucleotide sequencing of the cloned DNA.
- Mutational analysis of the prr locus.
Main Results:
- The prr locus encodes a latent form of anticodon nuclease, comprising a core enzyme and masking agents.
- Phage T4-encoded factors counteract the prr-encoded masking agents, leading to the activation of the latent nuclease.
- The study identified the specific cleavage-ligation of host tRNALys as the underlying mechanism of restriction.
Conclusions:
- The prr locus and phage T4 cooperate to regulate anticodon nuclease activity.
- This tRNA cleavage-ligation pathway, encoded by separate genetic systems, offers insights into the evolution of protein-mediated RNA splicing.