Promoter for the establishment of repressor synthesis in bacteriophage lambda

Area of Science:

• Molecular Biology
• Bacteriophage Genetics
• Gene Regulation

Background:

• The lambda repressor gene (cI) controls lysogeny in bacteriophage lambda.
• Transcription of the cI gene is positively regulated by phage proteins cII and cIII.
• Understanding the regulatory mechanisms of cI gene expression is crucial for bacteriophage lambda lifecycle studies.

Purpose of the Study:

• To isolate and characterize the 5'-terminal region of the cI gene transcript.
• To identify and analyze the promoter (pE) responsible for cI gene transcription initiation.
• To investigate the role of phage proteins cII and cIII in regulating pE activity.

Main Methods:

• RNA isolation and characterization of the 5'-terminal region.
• DNA sequencing of the promoter region.
• Analysis of cis-dominant mutations affecting promoter function.

Main Results:

• The 5'-terminal region of the cI transcript originates from a promoter (pE) located between the cro and cII genes.
• The DNA sequence of pE shows limited homology to other known promoters.
• Cis-dominant mutations (cY) in the -10 and -35 regions of pE abolish transcription initiation.

Conclusions:

• The promoter pE is essential for the transcription of the lambda repressor gene (cI).
• The -10 and -35 regions of pE are critical for promoter function and regulation.
• The -35 region is proposed as the site for activation by the cII protein, highlighting a direct protein-DNA interaction mechanism.