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Mu DNA reintegration upon excision: evidence for a possible involvement of nucleoid folding
L Paolozzi1, G Fabozzi1, P Ghelardini1
1Dipartimento di Biologia, Università 'Tor Vergata' Roma, Italy1.
Abstract:
Mutations induced by the integration of a Mugem2ts prophage can revert at frequencies around 1x10(-6). In these revertant clones, the prophage excised from its original localization is not lost but reintegrated elsewhere in the host genome. One of the most intriguing aspects of this process is that the prophage reintegration is not randomly distributed: there is a strong correlation between the original site of insertion (the donor site) and the target site of the phage DNA migration (the receptor site). In this paper, it is shown that in the excision-reintegration process mediated by Mugem2ts, the position of the initial prophage site strongly influences the location of the reintegration site. In addition, for each donor site, the receptor site is a discrete DNA region within which the excised Mu DNA can reintegrate and the two sites implicated in phage DNA migration must be located on the same DNA molecule. These data suggest the involvement of nucleoid folding in the excision-reintegration process.
Insights
Mu phage integration and excision are not random. The original insertion site (donor site) influences where the Mu phage DNA reintegrates (receptor site), suggesting nucleoid folding involvement.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Bacteriophage Mu is a model system for studying transposition.
- Prophage induction in Mu leads to excision and reintegration into the host genome.
- Previous studies indicated non-random integration patterns of Mu phage.
Purpose of the Study:
- To investigate the relationship between Mu phage donor and receptor sites during excision-reintegration.
- To determine if the initial insertion site influences subsequent reintegration locations.
- To explore the potential role of host DNA organization in Mu transposition.
Main Methods:
- Analysis of revertant clones from Mugem2ts prophage induction.
- Characterization of prophage excision and reintegration sites.
- Comparative genomics to identify donor and receptor site correlations.
Main Results:
- Mu phage excision-reintegration occurs at low frequencies (~1x10^-6).
- Reintegrated prophage DNA is found at new genomic locations, not lost.
- A strong correlation exists between the original donor site and the new receptor site.
- Receptor sites are discrete DNA regions, and both sites must be on the same DNA molecule.
Conclusions:
- The initial Mu prophage insertion site significantly influences its subsequent reintegration site.
- These findings suggest that host nucleoid organization plays a crucial role in directing Mu phage DNA transposition.
- Mu phage excision-reintegration is a directed process, not random, involving specific DNA-DNA interactions.