Characterization of the cts4 repressor mutation in transposable bacteriophage Mu

Area of Science:

• Molecular Biology
• Bacteriology
• Genetics

Background:

• Mucts4 is a thermoinducible derivative of transposable phage Mu, isolated over 30 years ago.
• It was the first available thermoinducible derivative of transposable phage Mu.
• Previously characterized thermoinducible Mu prophages, such as Mucts62, exhibit different lysogenization characteristics.

Purpose of the Study:

• To characterize the cts4 mutation and its corresponding mutant protein.
• To understand the molecular basis of the thermosensitivity and altered function of the Mucts4 repressor.
• To investigate the effect of the cts4 mutation on repressor-DNA and repressor-repressor interactions.

Main Methods:

• Characterization of the cts4 mutation (Leu129Val) within the repressor region.
• In vitro assessment of thermosensitive operator DNA binding of the cts4 repressor.
• Analysis of temperature-dependent protein-protein cross-linking patterns.
• Electrophoretic analysis of wild-type, Mucts62, and Mucts4 repressor proteins.
• Investigation of Mucts4 repressor binding to DNA fragments containing the early operator region.

Main Results:

• The Mucts4 repressor exhibits thermosensitive operator DNA binding in vitro.
• Temperature-dependent alterations in protein-protein cross-linking were observed for Mucts4 repressor.
• The Mucts4 repressor displayed a distinct electrophoretic profile compared to wild-type and Mucts62 repressors, especially at higher temperatures.
• Mucts4 repressor showed altered binding patterns to DNA fragments with the early operator region.
• The cts4 mutation appears to affect protein-protein interactions, potentially within the leucine-rich region.

Conclusions:

• The cts4 mutation (Leu129Val) in the Mu phage repressor leads to thermosensitive DNA binding and altered protein-protein interactions.
• These molecular defects contribute to the reduced lysogenization frequency of Mucts4, even at permissive temperatures.
• The findings provide insights into the structure-function relationships of the Mu repressor and its role in phage-Mu regulation.