Extent of sequence homology required for bacteriophage lambda site-specific recombination

Area of Science:

• Molecular Biology
• Genetics
• Virology

Background:

• Bacteriophage lambda integrates and excises DNA via site-specific recombination.
• This process involves homologous core regions within attachment (att) sites.
• Strand exchange occurs within a specific overlap region of the core.

Purpose of the Study:

• To investigate the role of sequence homology in bacteriophage lambda recombination.
• To determine the importance of homology within and outside the core overlap region.

Main Methods:

• Construction of point mutations within the core region of att sites.
• Assaying recombination activity in vivo and in vitro.
• Comparing recombination efficiency of wild-type and mutant att sites.

Main Results:

• Mutations outside the overlap region (-3 position) did not affect recombination.
• Mutations within the overlap region (-2 position) significantly reduced recombination with wild-type sites.
• Recombination was restored for -2 mutants when paired with homologous mutant sites.
• In vitro studies showed one homologous strand in the attB overlap region is sufficient for recombination.

Conclusions:

• Sequence homology is crucial within the overlap region of att sites for efficient bacteriophage lambda integration and excision.
• Homology outside the overlap region is not essential for this site-specific recombination process.