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- Ahlgren-Berg, Alexandra, et al.
(author)
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A comparative analysis of the bifunctional Cox proteins of two heteroimmune P2-like phages with different host integration sites
- 2009
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In: Virology. - : Elsevier BV. - 0042-6822 .- 1096-0341. ; 385:2, s. 303-12
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Journal article (peer-reviewed)abstract
- The Cox protein of the coliphage P2 is multifunctional; it acts as a transcriptional repressor of the Pc promoter, as a transcriptional activator of the P(LL) promoter of satellite phage P4, and as a directionality factor for site-specific recombination. The Cox proteins constitute a unique group of directionality factors since they couple the developmental switch with the integration or excision of the phage genome. In this work, the DNA binding characteristics of the Cox protein of WPhi, a P2-related phage, are compared with those of P2 Cox. P2 Cox has been shown to recognize a 9 bp sequence, repeated at least 6 times in different targets. In contrast to P2 Cox, WPhi Cox binds with a strong affinity to the early control region that contains an imperfect direct repeat of 12 nucleotides. The removal of one of the repeats has drastic effects on the capacity of WPhi to bind to the Pe-Pc region. Again in contrast to P2 Cox, WPhi Cox has a lower affinity to attP compared to the Pe-Pc region, and a repeat of 9 bp can be found that has 5 bp in common with the repeat in the Pe-Pc region. WPhi Cox, however, is essential for excisive recombination in vitro. WPhi Cox, like P2 Cox, binds cooperatively with integrase to attP. Both Cox proteins induce a strong bend in their DNA targets upon binding.
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| 2. |
- Ahlgren-Berg, Alexandra, et al.
(author)
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A comparison of the DNA binding and bending capacities and the oligomeric states of the immunity repressors of heteroimmune coliphages P2 and W Phi
- 2007
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In: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 35:10, s. 3167-3180
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Journal article (peer-reviewed)abstract
- Bacteriophages P2 and W Phi are heteroimmune members of the P2-like family of temperate Escherichia coli phages. Temperate phages can grow lytically or form lysogeny after infection. A transcriptional switch that contains two convergent promoters, Pe and Pc, and two repressors regulate what life mode to enter. The immunity repressor C is the first gene of the lysogenic operon, and it blocks the early Pe promoter. In this work, some characteristics of the C proteins of P2 and W Phi are compared. An in vivo genetic analysis shows that W Phi C, like P2C, has a strong dimerization activity in the absence of its DNA target. Both C proteins recognize two directly repeated sequences, termed half-sites and a strong bending is induced in the respective DNA target upon binding. P2C is unable to bind to one half-site as opposed to W Phi, but both half-sites are required for repression of W Phi Pe. A reduction from three to two helical turns between the centers of the half-sites in W Phi has no significant effect on the capacity to repress Pe. However, the protein-DNA complexes formed differ, as determined by electrophoretic mobility shift experiments. A difference in spontaneous phage production is observed in isogenic lysogens.
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| 3. |
- Berntsson, Ronnie P. -A., et al.
(author)
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Structural insight into DNA binding and oligomerization of the multifunctional Cox protein of bacteriophage P2
- 2014
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In: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 42:4, s. 2725-2735
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Journal article (peer-reviewed)abstract
- The Cox protein from bacteriophage P2 is a small multifunctional DNA-binding protein. It is involved in site-specific recombination leading to P2 prophage excision and functions as a transcriptional repressor of the P2 Pc promoter. Furthermore, it transcriptionally activates the unrelated, defective prophage P4 that depends on phage P2 late gene products for lytic growth. In this article, we have investigated the structural determinants to understand how P2 Cox performs these different functions. We have solved the structure of P2 Cox to 2.4 angstrom resolution. Interestingly, P2 Cox crystallized in a continuous oligomeric spiral with its DNA-binding helix and wing positioned outwards. The extended C-terminal part of P2 Cox is largely responsible for the oligomerization in the structure. The spacing between the repeating DNA-binding elements along the helical P2 Cox filament is consistent with DNA binding along the filament. Functional analyses of alanine mutants in P2 Cox argue for the importance of key residues for protein function. We here present the first structure from the Cox protein family and, together with previous biochemical observations, propose that P2 Cox achieves its various functions by specific binding of DNA while wrapping the DNA around its helical oligomer.
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