title: The cell pole: the site of cross talk between the DNA uptake and genetic recombination machinery.
abstract: Natural transformation is a programmed mechanism characterized by binding of free double-stranded (ds) DNA from the environment to the cell pole in rod-shaped bacteria. In Bacillus subtilis some competence proteins, which process the dsDNA and translocate single-stranded (ss) DNA into the cytosol, recruit a set of recombination proteins mainly to one of the cell poles. A subset of single-stranded binding proteins, working as "guardians", protects ssDNA from degradation and limit the RecA recombinase loading. Then, the "mediators" overcome the inhibitory role of guardians, and recruit RecA onto ssDNA. A RecA·ssDNA filament searches for homology on the chromosome and, in a process that is controlled by "modulators", catalyzes strand invasion with the generation of a displacement loop (D-loop). A D-loop resolvase or "resolver" cleaves this intermediate, limited DNA replication restores missing information and a DNA ligase seals the DNA ends. However, if any step fails, the "rescuers" will repair the broken end to rescue chromosomal transformation. If the ssDNA does not share homology with resident DNA, but it contains information for autonomous replication, guardian and mediator proteins catalyze plasmid establishment after inhibition of RecA. DNA replication and ligation reconstitute the molecule (plasmid transformation). In this review, the interacting network that leads to a cross talk between proteins of the uptake and genetic recombination machinery will be placed into prospective.
authors.affiliation: Departments of Therapeutic Radiology and Genetics, Yale University School of Medicine, New Haven, CT, USA.
authors.forename: Dawit
authors.initials: D
authors.lastname: Kidane
authors.forename: Silvia
authors.initials: S
authors.lastname: Ayora
authors.forename: Joann B
authors.initials: JB
authors.lastname: Sweasy
authors.forename: Peter L
authors.initials: PL
authors.lastname: Graumann
authors.forename: Juan C
authors.initials: JC
authors.lastname: Alonso
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D004260:DNA Repair; D004261:DNA Replication; D061269:DNA Transformation Competence; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D022761:Gene Transfer, Horizontal; D010957:Plasmids; D011938:Rec A Recombinases / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic
chemical_list: D001426:Bacterial Proteins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D004247:DNA; D011938:Rec A Recombinases