Nucleic Acids Research Advance Access originally published online on May 7, 2007
Nucleic Acids Research 2007 35(10):3167-3180; doi:10.1093/nar/gkm171
Nucleic Acids Research, 2007, Vol. 35, No. 10 3167-3180
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Molecular Biology |
A comparison of the DNA binding and bending capacities and the oligomeric states of the immunity repressors of heteroimmune coliphages P2 and W
Department of Genetics, Microbiology and Toxicology, Stockholm University, S-106 91 Stockholm, Sweden
*To whom correspondence should be addressed. Tel: +46 8 161270; Fax: +46 8 164315; Email: Elisabeth.Haggard{at}gmt.su.se
Received August 11, 2006. Revised March 5, 2007. Accepted March 6, 2007.
Bacteriophages P2 and W
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 con-vergent 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 are compared. An in vivo genetic analysis shows that W C, like P2 C, 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. P2 C is unable to bind to one half-site as opposed to W, but both half-sites are required for repression of W Pe. A reduction from three to two helical turns between the centers of the half-sites in W 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.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors