title: Binding Specificities of the Telomere Phage ϕKO2 Prophage Repressor CB and Lytic Repressor Cro.
abstract: Temperate bacteriophages possess a genetic switch which regulates the lytic and lysogenic cycle. The genomes of the temperate telomere phages N15, PY54, and ϕKO2 harbor a primary immunity region (immB) comprising genes for the prophage repressor (cI or cB), the lytic repressor (cro) and a putative antiterminator (q). The roles of these products are thought to be similar to those of the lambda proteins CI (CI prophage repressor), Cro (Cro repressor), and Q (antiterminator Q), respectively. Moreover, the gene order and the location of several operator sites in the prototype telomere phage N15 and in ϕKO2 are reminiscent of lambda-like phages. We determined binding sites of the ϕKO2 prophage repressor CB and lytic repressor Cro on the ϕKO2 genome in detail by electrophoretic mobility shift assay (EMSA) studies. Unexpectedly, ϕKO2 CB and Cro revealed different binding specificities. CB was bound to three OR operators in the intergenic region between cB and cro, two OL operators between cB and the replication gene repA and even to operators of N15. Cro bound exclusively to the 16 bp operator site OR3 upstream of the ϕKO2 prophage repressor gene. The ϕKO2 genes cB and cro are regulated by several strong promoters overlapping with the OR operators. The data suggest that Cro represses cB transcription but not its own synthesis, as already reported for PY54 Cro. Thus, not only PY54, but also phage ϕKO2 possesses a genetic switch that diverges significantly from the switch of lambda-like phages.
authors.affiliation: Bundesinstitut für Risikobewertung (Federal Institute for Risk Assessment), Department of Biological Safety, Diedersdorfer Weg 1, D-12277 Berlin, Germany. jens-andre.hammerl@bfr.bund.de.
authors.forename: Jens Andre
authors.initials: JA
authors.lastname: Hammerl
authors.affiliation: Bundesinstitut für Risikobewertung (Federal Institute for Risk Assessment), Department of Biological Safety, Diedersdorfer Weg 1, D-12277 Berlin, Germany. claudia.jaeckel@bfr.bund.de.
authors.forename: Claudia
authors.initials: C
authors.lastname: Jäckel
authors.affiliation: Max-Planck-Institut für Molekulare Genetik, Ihnestraße 63-73, D-14195 Berlin, Germany. lanka@molgen.mpg.de.
authors.forename: Erich
authors.initials: E
authors.lastname: Lanka
authors.affiliation: Institute of Animal Hygiene and Environmental Health, Free University Berlin, Robert-von-Ostertag-Str. 7-13, D-14163 Berlin, Germany. nicole.roschanski@fu-berlin.de.
authors.forename: Nicole
authors.initials: N
authors.lastname: Roschanski
authors.affiliation: Bundesinstitut für Risikobewertung (Federal Institute for Risk Assessment), Department of Biological Safety, Diedersdorfer Weg 1, D-12277 Berlin, Germany. stefan.hertwig@bfr.bund.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Hertwig
mesh_terms: D001435:Bacteriophages / Q000201:enzymology* / Q000235:genetics; D001665:Binding Sites; D004279:DNA, Viral / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D023061:Gene Order; D005814:Genes, Viral; D009875:Operator Regions, Genetic; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism*; D013379:Substrate Specificity; D026801:Synteny; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D004279:DNA, Viral; D012097:Repressor Proteins; D014764:Viral Proteins
keywords: DNA binding; N15; PY54; genetic switch; immunity region; lytic repressor Cro; prophage repressor CB; telomere phages ϕKO2