title: Deletion of porA by recombination between clusters of repetitive extragenic palindromic sequences in Neisseria meningitidis.
abstract: PorA is an important component in a vaccine against infection with Neisseria meningitidis. However, porA-negative meningococci were isolated from patients, thereby potentially limiting the role of PorA-mediated immunity. To analyze the mechanism by which the porA deletion occurred, the regions upstream and downstream of porA from three meningococcal strains (H44/76, H355, and 860183) were sequenced. The porA upstream region in strain 860183 contains a cluster of 22 repetitive palindromic RS3 core sequences (ATTCCC-N8-GGGAAT) and 10 RS3 core sequences (ATTCCC) in direct orientation. The cluster is flanked by neisserial repeats, so-called Correia elements, and can be subdivided into three repeats of 518 bp followed by a truncated repeat. The porA upstream region of the other two strains showed deletions, probably caused by a recombination between RS3 core sequences. The porA downstream region of H44/76 and H355 contains the IS1106 element followed by a cluster of 10 palindromic RS3 core sequences, 4 RS3 core sequences, and 1 other RS3 core sequence (GGGAAT) and is followed by a Correia element. This cluster can be subdivided into four direct repeats of 370 bp. Strain 860183 had two such repeats instead of four. Sequence analysis of the porA-negative variants indicated that the deletion of porA occurred via a recombination between two copies of the 116-bp region, containing two palindromic RS3 core sequences and a single RS3 core sequence. This region is homologous in the upstream and downstream clusters.
authors.affiliation: Department of Medical Microbiology and Reference Laboratory for Bacterial Meningitis, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. A.VANDERENDE@amc.uva.nl
authors.forename: A
authors.initials: A
authors.lastname: van der Ende
authors.forename: C T
authors.initials: CT
authors.lastname: Hopman
authors.forename: J
authors.initials: J
authors.lastname: Dankert
mesh_terms: D001483:Base Sequence; D004269:DNA, Bacterial; D017353:Gene Deletion; D014644:Genetic Variation; D006801:Humans; D008589:Meningococcal Infections / Q000382:microbiology; D008969:Molecular Sequence Data; D005810:Multigene Family; D009345:Neisseria meningitidis / Q000235:genetics* / Q000302:isolation & purification; D018272:Porins / Q000235:genetics*; D011995:Recombination, Genetic
chemical_list: D004269:DNA, Bacterial; D018272:Porins; C057699:porin protein, Neisseria