title: Control of directionality in Streptomyces phage φBT1 integrase-mediated site-specific recombination.
abstract: Streptomyces phage φBT1 integrates its genome into the attB site of the host chromosome with the attP site to generate attL and attR. The φBT1 integrase belongs to the large serine recombinase subfamily which directly binds to target sites to initiate double strand breakage and exchange. A recombination directionality factor (RDF) is commonly required for switching integration to excision. Here we report the characterization of the RDF protein for φBT1 recombination. The RDF, is a phage-encoded gp3 gene product (28 KDa), which allows efficient active excision between attL and attR, and inhibits integration between attB and attP; Gp3 can also catalyze topological relaxation with the integrase of supercoiled plasmids containing a single excision site. Further study showed that Gp3 could form a dimer and interact with the integrase whether it bound to the substrate or not. The synapse formation of attL or attR alone with integrase and Gp3 showed that synapsis did not discriminate between the two sites, indicating that complementarity of central dinucleotides is the sole determinant of outcome in correct excision synapses. Furthermore, both in vitro and in vivo evidence support that the RDFs of φBT1 and φC31 were fully exchangeable, despite the low amino acid sequence identity of the two integrases.
authors.affiliation: Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, China ; Key Laboratory of Synthetic biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
authors.forename: Binyan
authors.initials: B
authors.lastname: Zhu
authors.forename: Ruixue
authors.initials: R
authors.lastname: Dai
authors.forename: Guoping
authors.initials: G
authors.lastname: Zhao
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Ding
mesh_terms: D001435:Bacteriophages / Q000502:physiology*; D001483:Base Sequence; D002384:Catalysis; D017931:DNA Primers; D024202:Electrophoretic Mobility Shift Assay; D019426:Integrases / Q000378:metabolism*; D011995:Recombination, Genetic; D013302:Streptomyces / Q000821:virology*; D013379:Substrate Specificity; D010948:Viral Plaque Assay
chemical_list: D017931:DNA Primers; D019426:Integrases