Vibrio cholerae LexA coordinates CTX prophage gene expression

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• The CTX Phi bacteriophage carries cholera toxin genes and infects Vibrio cholerae.
• Phage gene expression is tightly regulated by phage and host factors.

Purpose of the Study:

• To elucidate the regulatory mechanism of the rstR promoter (P(R)) in CTX Phi.
• To understand the role of RstR and LexA in CTX Phi gene regulation.

Main Methods:

• Identification and characterization of the P(R) promoter.
• Analysis of RstR and LexA binding sites and their effects on transcription.
• Investigating RstR autoregulation and LexA coactivation.

Main Results:

• RstR autoregulates its own expression from the P(R) promoter, exhibiting both positive and negative control.
• LexA is essential for RstR-mediated activation of P(R) transcription.
• LexA binds to an SOS box within the P(R) spacer region, acting as a coactivator.
• LexA represses P(A) and coactivates P(R), coordinating phage transcription.

Conclusions:

• A novel gene regulatory circuit involving RstR and LexA is identified in CTX Phi.
• LexA plays a dual role in repressing CTX Phi virulence genes (P(A)) and coactivating phage gene expression (P(R)).
• This regulatory circuit is predicted to exhibit transient switch behavior upon prophage induction.