Daughter origins can be held together by O protein in phage lambda replicative intermediates

Area of Science:

• Molecular Biology
• Genetics
• Virology

Background:

• Lambda phage replication involves initiator protein O binding to origin DNA.
• Understanding the structural organization of these complexes is crucial for deciphering replication initiation mechanisms.

Purpose of the Study:

• To investigate the molecular interactions of lambda initiator protein O with replicative intermediates.
• To elucidate the structural consequences of O protein binding to lambda origins.

Main Methods:

• Incubation of lambda replicative intermediates with initiator protein O.
• Sequential incubation with single-stranded binding protein and O protein.
• Analysis of DNA structures formed by O protein binding to tandem origin sequences on plasmids.

Main Results:

• O protein forms complex molecules by interacting with both daughter origin segments and growing points.
• Simpler structures are observed when O protein binds to origins after single-stranded binding protein, with both daughter origins bound by O.
• O protein binding to tandem lambda origins on plasmids results in DNA loop formation.

Conclusions:

• Double origin binding by O protein creates topological domains.
• These topological domains have significant implications for the initiation of replication at daughter origins.