title: Control of Staphylococcus aureus pathogenicity island excision.
abstract: Staphylococcus aureus pathogenicity islands (SaPIs) are a group of related 15-17 kb mobile genetic elements that commonly carry genes for superantigen toxins and other virulence factors. The key feature of their mobility is the induction of SaPI excision and replication by certain phages and their efficient encapsidation into specific small-headed phage-like infectious particles. Previous work demonstrated that chromosomal integration depends on the SaPI-encoded recombinase, Int. However, although involved in the process, Int alone was not sufficient to mediate efficient SaPI excision from chromosomal sites, and we expected that SaPI excision would involve an Xis function, which could be encoded by a helper phage or by the SaPI, itself. Here we report that the latter is the case. In vivo recombination assays with plasmids in Escherichia coli demonstrate that SaPI-coded Xis is absolutely required for recombination between the SaPI att(L) and att(R) sites, and that both sites, as well as their flanking SaPI sequences, are required for SaPI excision. Mutational analysis reveals that Xis is essential for efficient horizontal SaPI transfer to a recipient strain. Finally, we show that the master regulator of the SaPI life cycle, Stl, blocks expression of int and xis by binding to inverted repeats present in the promoter region, thus controlling SaPI excision.
authors: Centro de Investigación y Tecnología Animal, Instituto Valenciano de Investigaciones Agrarias, Apdo. 187, 12.400 Segorbe, Castellón, Spain.
authors: Ignacio
authors: I
authors: Mir-Sanchis
authors: Roser
authors: R
authors: Martínez-Rubio
authors: Miguel
authors: M
authors: Martí
authors: John
authors: J
authors: Chen
authors: Íñigo
authors: Í
authors: Lasa
authors: Richard P
authors: RP
authors: Novick
authors: María Ángeles
authors: MÁ
authors: Tormo-Más
authors: José R
authors: JR
authors: Penadés
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D004252:DNA Mutational Analysis; D044404:Genomic Islands / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D011995:Recombination, Genetic / Q000235:genetics; D013211:Staphylococcus aureus / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins