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Nucleotide sequence of the operators of lambda ultravirulent mutants
Nucleic Acids Research
|May 24, 1980
Summary
Ultravirulent lambda phages possess multiple mutations in operator sequences (OL1, OL2, OR1, OR2) enabling growth in high repressor conditions. These changes lead to constitutive promoter expression, even with high repressor or cro protein levels.
Area of Science:
- Bacteriophage genetics
- Molecular biology
- Genomics
Background:
- Bacteriophage lambda's virulence is regulated by repressor proteins and operator sequences.
- Ultravirulent mutants exhibit altered growth characteristics in host cells with high repressor levels.
Purpose of the Study:
- To determine the nucleotide sequences of operators in ultravirulent lambda mutants.
- To understand the genetic basis of ultravirulence in bacteriophage lambda.
Main Methods:
- Nucleotide sequencing of operator regions (OL1, OL2, OL3, OR1, OR2, OR3) in ultravirulent lambda mutants.
- Comparative analysis of wild-type and mutant operator sequences.
Main Results:
- Ultravirulence in lambda phages is associated with multiple mutations within operator sequences.
- Mutations were identified in OL1, OL2, and OR2, and two mutations in OR1, but not in OR3.
- The mutated operator structure results in constitutive expression of the PR promoter.
Conclusions:
- Ultravirulence requires multiple mutational events at specific operator sites (OL1, OL2, OR1, OR2).
- These mutations confer resistance to high levels of lambda repressor and cro gene product.
- A model for lambda operator structure suggests distinct functional subsets for repressor recognition and stabilization.