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Updated: Jul 10, 2026
06:10
Following Cell-fate in E. coli After Infection by Phage Lambda
Published on: October 14, 2011
Cooperative DNA binding by CI repressor is dispensable in a phage lambda variant.
Andrea C Babić1, John W Little
1Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, AZ 85721, USA.
Summary
The phage lambda CI protein's cooperative DNA binding is not essential for lysogenic and lytic circuit functions. Cooperativity appears to be a refinement that enhances lysogen stability under varying conditions.
Area of Science:
- Molecular Biology
- Genetics
- Virology
Background:
- Gene regulatory circuits involve complex interactions, with components potentially being essential or refinements.
- The phage lambda CI protein regulates the lysogenic state by binding operators.
Purpose of the Study:
- To investigate if the cooperative DNA binding of the CI protein is essential for phage lambda regulatory circuit function.
- To determine the role of CI cooperativity in lysogen stability and switching behavior.
Main Methods:
- Generated a mutant phage lacking CI cooperativity.
- Introduced suppressor mutations to compensate for the loss of cooperativity.
- Assessed the ability of mutant phages to form stable lysogens, switch to lytic growth, and exhibit threshold responses.
Main Results:
- A mutant phage lacking CI cooperativity could not form stable lysogens initially.
- Suppressor mutations restored the ability to form stable lysogens and exhibit wild-type switching behavior.
- Cooperative DNA binding by CI is not essential for basic circuit functions when CI levels are increased.
Conclusions:
- Cooperative DNA binding by the phage lambda CI protein is not essential for lysogenic stability and lytic switching.
- Cooperativity likely serves as a refinement that increases lysogen stability against environmental fluctuations.
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