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DNA binding by the coliphage 186 repressor protein CI
The Journal of Biological Chemistry
|May 10, 1996
Summary
The coliphage 186 cI protein binds to specific DNA operator sites to maintain lysogeny and immunity. It recognizes two distinct DNA sequences and exhibits cooperative binding, with multimers forming the active DNA-binding species.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- The cI gene of coliphage 186 is crucial for maintaining lysogeny and conferring immunity.
- The cI protein represses key promoters, including p(R) and p(B), to control viral gene expression.
Purpose of the Study:
- To investigate the DNA binding sites and mechanisms of the coliphage 186 cI protein.
- To understand how cI protein binding confers immunity and maintains lysogeny.
Main Methods:
- Gel mobility shift assays to detect protein-DNA interactions.
- DNase I footprinting to precisely map protein binding sites on DNA.
- Genetic analysis of virulence mutations affecting cI binding.
Main Results:
- Identified multiple cI operator sites at p(R), p(B), FL, and FR regions.
- Discovered that cI protein recognizes two distinct DNA sequence types (Type A/A' and Type B).
- Demonstrated cooperative binding of cI to adjacent operators, essential for p(R) binding, with high-order multimers as the active species.
Conclusions:
- Coliphage 186 cI protein utilizes distinct DNA binding sequences and cooperative interactions to regulate viral gene expression.
- Understanding these mechanisms provides insight into viral lysogeny and immunity.
- The multimeric nature of the cI protein is key to its DNA binding efficiency.