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Frameshift mutations in the bacteriophage Mu repressor gene can confer a trans-dominant virulent phenotype to the
V Geuskens1, J L Vogel, R Grimaud
1Laboratoire de Génétique, Université Libre de Bruxelles, Rhode Saint Genèse, Belgium.
Abstract:
Virulent mutations in the bacteriophage Mu repressor gene were isolated and characterized. Recombination and DNA sequence analysis have revealed that virulence is due to unusual frameshift mutations which change several C-terminal amino acids. The vir mutations are in the same repressor region as the sts amber mutations which, by eliminating several C-terminal amino acids, suppress thermosensitivity of repressor binding to the operators by its N-terminal domain (J. L. Vogel, N. P. Higgins, L. Desmet, V. Geuskens, and A. Toussaint, unpublished data). Vir repressors bind Mu operators very poorly. Thus the Mu repressor C terminus, either by itself or in conjunction with other phage or host proteins, tunes the DNA-binding properties at the repressor N terminus.
Insights
Virulent mutations in bacteriophage Mu repressor genes result from frameshift mutations. These mutations alter C-terminal amino acids, impairing repressor binding to DNA operators.
Area of Science:
- Molecular biology
- Virology
- Genetics
Background:
- Bacteriophage Mu is a temperate bacteriophage with a complex regulatory system.
- The phage Mu repressor protein controls viral gene expression by binding to operator DNA sequences.
- Understanding repressor function is crucial for deciphering viral life cycles and host interactions.
Purpose of the Study:
- To investigate the molecular basis of virulence in bacteriophage Mu.
- To characterize mutations affecting the bacteriophage Mu repressor gene.
- To elucidate the role of the repressor's C-terminal domain in DNA binding and regulation.
Main Methods:
- Isolation and characterization of virulent (vir) mutations in the bacteriophage Mu repressor gene.
- Recombination analysis to identify mutation locations.
- DNA sequencing to determine the precise genetic changes.
- Functional assays to assess repressor-operator binding affinity.
Main Results:
- Identified unusual frameshift mutations in the bacteriophage Mu repressor gene as the cause of virulence.
- These mutations result in altered C-terminal amino acids of the repressor protein.
- Virulent repressors exhibit significantly reduced binding affinity to Mu operators.
- The C-terminal region of the repressor influences the DNA-binding properties of the N-terminal domain.
Conclusions:
- The C-terminal domain of the bacteriophage Mu repressor plays a critical role in modulating DNA-binding activity.
- Frameshift mutations leading to altered C-terminal amino acids can disrupt repressor function and confer virulence.
- These findings highlight the intricate relationship between repressor structure, DNA binding, and phage regulation.