A CII-responsive promoter within the Q gene of bacteriophage lambda

Area of Science:

• Molecular Biology
• Bacteriophage Genetics

Background:

• The phage lambda Q gene is crucial for late gene expression during the lysogenic cycle.
• The CII protein is a key regulator of phage lambda's lysogenic pathway, controlling early gene transcription.
• Previous studies identified CII-activated promoters pE and pI involved in lysogenic control.

Purpose of the Study:

• To investigate a newly identified DNA site within the phage lambda Q gene for potential promoter activity.
• To determine if this site functions as a CII-activated promoter in vivo.
• To understand the role of this novel promoter in regulating Q gene expression and the lysogenic response.

Main Methods:

• Homology searches identified a potential CII-activated promoter site within the Q gene.
• A DNA fragment containing the putative promoter was cloned into a reporter plasmid for beta-galactosidase expression.
• In vivo experiments involved co-expressing the cloned promoter with the CII protein from a compatible plasmid.

Main Results:

• The identified site, designated PaQ, demonstrated CII-activated transcription in vitro.
• In vivo, PaQ was activated by the CII protein, leading to significant beta-galactosidase production.
• Transcription initiated by PaQ occurs in the opposite direction to Q gene transcription.

Conclusions:

• The PaQ site functions as a genuine CII-activated promoter in vivo.
• This promoter's anti-sense transcription can interfere with Q gene expression.
• PaQ represents a novel mechanism for CII-mediated regulation of phage lambda's lysogenic response.