The rex region of bacteriophage lambda: two genes under three-way control

Area of Science:

• Bacteriophage genetics
• Molecular biology

Background:

• The phage lambda immunity region contains genes regulating phage-host interactions.
• The rexA and rexB genes are key components of the phage lambda Rex phenotype, responsible for excluding superinfecting phages.

Purpose of the Study:

• To elucidate the genetic organization and expression of the phage lambda rex region.
• To understand the regulatory mechanisms governing rexA and rexB gene expression.
• To investigate the functional roles of rexA and rexB proteins in phage lambda infection cycles.

Main Methods:

• Nucleotide sequencing of the phage lambda rex region.
• Analysis of gene expression from different promoters (p rm, p re, p lit).
• Investigating the role of rexB in DNA replication during lysogenic and lytic cycles.

Main Results:

• The rex region spans 1428 bp, encoding rexA and rexB.
• Co-regulated expression of rexA and rexB from p rm and p re drives the Rex phenotype.
• A separate promoter, p lit, allows rexB expression without rexA via a 470-nucleotide transcript.
• rexB protein appears to have auxiliary functions in both lysogenization and lytic infection.

Conclusions:

• Phage lambda rex gene expression is tightly regulated, allowing for both coordinated and non-coordinated expression.
• The rexB protein likely plays a multifaceted role in phage lambda's life cycle, impacting DNA replication and host interactions.