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Mutations in bacteriophage lambda repressor that prevent RecA-mediated cleavage
Abstract:
In this paper, we report on the isolation and sequence analysis of mutations that confer an induction-deficient phenotype to lambda repressor. A total of 16 different mutations, which occur at 13 different sites in the repressor gene, have been characterized. For most of the mutant lysogens, frequencies of spontaneous induction in a recA+ strain were reduced dramatically in comparison with those for a wild-type phage, and these mutant lysogens showed little or no prophage induction after UV irradiation. The immunity properties of cells containing the mutant repressors show that all of the mutants but one exhibit operator-binding properties indistinguishable from wild-type repressor.
Insights
Researchers identified 16 mutations in the lambda repressor gene that prevent phage induction. These mutations significantly reduce spontaneous and UV-induced prophage activation, impacting bacterial immunity.
Area of Science:
- Molecular Biology
- Genetics
- Virology
Background:
- Bacteriophage lambda repressor controls lysogenic or lytic cycles.
- Prophage induction, often triggered by DNA damage, leads to viral replication.
- Understanding repressor function is key to controlling phage-host interactions.
Purpose of the Study:
- To isolate and characterize mutations affecting lambda repressor's induction phenotype.
- To investigate the role of specific repressor mutations in prophage stability.
- To analyze the impact of these mutations on bacterial immunity.
Main Methods:
- Isolation of lambda repressor mutants.
- Sequence analysis of identified mutations.
- Characterization of mutant lysogens for spontaneous and UV-induced induction frequencies.
- Assessment of operator-binding properties of mutant repressors.
Main Results:
- 16 distinct mutations were identified at 13 different sites in the repressor gene.
- Mutant lysogens exhibited significantly reduced spontaneous induction.
- Mutant lysogens showed minimal to no prophage induction after UV irradiation.
- Most mutants retained wild-type operator-binding affinity, suggesting induction defects are not due to impaired DNA binding.
Conclusions:
- Specific mutations in the lambda repressor gene can confer an induction-deficient phenotype.
- These mutations stabilize the lysogenic state by preventing prophage activation.
- The findings provide insights into the regulatory mechanisms of phage-host interactions and bacterial immunity.