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Abnormal cointegrate structures mediated by gene B mutants of phage Mu: their implications with regard to gene
Abstract:
A system where the transposition of MupApl (a derivative of phage Mu carrying a determinant coding for ampicillin resistance) is followed from the small plasmid pML2 into the conjugative plasmid R388 has been used to investigate the influence on Mu transposition of B, an early Mu gene which is involved in normal phage DNA synthesis. In the absence of active B protein a low level (about 1% of normal) of transposition was detected. Roughly a third of these transpositional events was found to lead to the formation of cointegrate DNA structures which were shown to consist of R388, two complete copies of Mu and part only of pML2. The pML2 deletions vary in size but all those investigated appear to originate at an end of Mu. An explanation of these observations is proposed which envisages the B protein as part of the normal transposition complex.
Insights
The study investigated the role of the Mu gene B protein in transposition. Even without active B protein, transposition occurred at a low level, forming cointegrate DNA structures with deletions.
Area of Science:
- Molecular Biology
- Bacteriophage Genetics
- Transposable Elements
Background:
- Bacteriophage Mu is a key model for studying DNA transposition.
- The early gene B is essential for normal Mu DNA replication and transposition.
Purpose of the Study:
- To investigate the influence of the Mu gene B protein on transposition efficiency.
- To characterize transposition products formed in the absence of active B protein.
Main Methods:
- Utilized a system tracking MupApl transposition from plasmid pML2 to R388.
- Analyzed cointegrate DNA structures formed during transposition.
Main Results:
- Low-level transposition (1% of normal) was observed without active B protein.
- Cointegrate structures involving R388, two Mu copies, and pML2 deletions were formed.
- pML2 deletions originated at the ends of Mu.
Conclusions:
- The B protein is likely a component of the normal Mu transposition complex.
- Mu transposition can occur at a basal level independent of active B protein, leading to specific cointegrate structures.