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Isolation of point mutations in bacteriophage Mu attachment regions cloned in a lambda::mini-Mu phage
Abstract:
Twenty-one derivatives of a lambda::mini-Mu phage containing point mutations in the Mu attachment regions were isolated after mutD mutagenesis and selection for relief from Mu-specific replicative interference of lambda growth. DNA sequence analysis revealed that the single left-end mutant had suffered a T----C transition at position 1 of the Mu sequence, while the remaining 20 right-end mutants contained single base-pair insertions or deletions within the terminal 19 base pairs. A genetic assay showed that the right-end mutations revealed by sequencing were necessary for relief of the replicative inhibition of lambda growth. The properties of these mutants suggest that the terminal 2-base-pair and subterminal 8-base-pair inverted repeats are important for Mu-specific replicative transposition.
Insights
Mutations in the Mu phage attachment sites, specifically within the terminal inverted repeats, relieve lambda phage growth inhibition. These findings highlight the role of these repeats in Mu transposition.
Area of Science:
- Molecular Biology
- Genetics
- Virology
Background:
- Bacteriophage lambda and mini-Mu phage interactions are complex.
- Mu-specific replicative interference can inhibit lambda phage growth.
Purpose of the Study:
- To investigate the role of Mu phage attachment regions in replicative interference.
- To identify specific mutations that relieve Mu-mediated inhibition of lambda growth.
Main Methods:
- Mutagenesis using mutD to generate mini-Mu phage derivatives.
- Selection for mutants that overcome Mu-specific replicative interference.
- DNA sequencing to identify point mutations in Mu attachment regions.
- Genetic assays to confirm the functional significance of identified mutations.
Main Results:
- Twenty-one mini-Mu phage derivatives with mutations in attachment regions were isolated.
- A left-end mutation involved a T to C transition at Mu sequence position 1.
- Twenty right-end mutants exhibited single base-pair insertions or deletions within the terminal 19 base pairs.
- Right-end mutations were essential for relieving lambda growth inhibition.
Conclusions:
- The terminal 2-base-pair and subterminal 8-base-pair inverted repeats are crucial for Mu-specific replicative transposition.
- Mutations within these inverted repeats alter Mu phage function and interaction with lambda phage.