The pathogenic Neisseria are obligate human pathogens that rely on several antigenic variation systems to continually colonize and cause disease in the human population. This proposal will further our studies into the molecular mechanisms used to allow pilin antigenic variation in Neisseria gonorrhoeae. High frequency changes in the pilin amino acid sequence are mediated by gene conversion reactions between one of 18 silent pilin copies and the single expressed pilin gene. In the past funding period, we have identified most of the proteins involved in this process and have demonstrated that the pathogenic Neisseria carry diploid chromosomes that may facilitate gene conversion. We have additionally shown that both the formation of an alternative DNA structure called a guanine quartet (G4), and the transcription of a small RNA within the G4 are required for pilin antigenic variation. In the next funding period we will determine the role of G4 transcription during pilin antigenic variation. Proteins that bind the G4 structure will be identified and we will test whethe these proteins stimulate G4 structure formation or dissolution, and/or the process of pilin antigenic variation. We will also determine whether the G4 structure acts to promote recombination by blocking DNA replication and whether specific helicases prevent a replication stall. We will probe for formation of the G4 structure within the bacterial chromosome and determine whether the G4 structure associates with other DNA sequences. Finally, the effect of various partial loss-of-function mutations on pilin antigenic variation will be determined. The results of these innovative studies will have great impact on the study of Neisserial pathogenesis, mechanisms of antigenic variation, DNA recombination and replication, and the role of alternative DNA structures on molecular processes in many cell types.
The pathogenic Neisseria are obligate human pathogens that have had a long evolutionary history within human populations. The studies outlined in this proposal will continue our investigations into the molecular mechanisms used for high frequency variation of the bacterial pilus, which allows the organism to evade the adaptive immune system and continually infect susceptible individuals.
|ChÃ¢teau, Alice; Seifert, H Steven (2016) Neisseria gonorrhoeae survives within and modulates apoptosis and inflammatory cytokine production of human macrophages. Cell Microbiol 18:546-60|
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|Palmer, Guy H; Bankhead, Troy; Seifert, H Steven (2016) Antigenic Variation in Bacterial Pathogens. Microbiol Spectr 4:|
|Peak, Ian R; Chen, Adrienne; Jen, Freda E-C et al. (2016) Neisseria meningitidis Lacking the Major Porins PorA and PorB Is Viable and Modulates Apoptosis and the Oxidative Burst of Neutrophils. J Proteome Res 15:2356-65|
|Lenz, Jonathan D; Stohl, Elizabeth A; Robertson, Rosanna M et al. (2016) Amidase Activity of AmiC Controls Cell Separation and Stem Peptide Release and Is Enhanced by NlpD in Neisseria gonorrhoeae. J Biol Chem 291:10916-33|
|Rotman, Ella; Seifert, H Steven (2015) Neisseria gonorrhoeae MutS affects pilin antigenic variation through mismatch correction and not by pilE guanine quartet binding. J Bacteriol 197:1828-38|
|Obergfell, Kyle P; Seifert, H Steven (2015) Mobile DNA in the pathogenic Neisseria. Microbiol Spectr 3:|
|Obergfell, Kyle P; Seifert, H Steven (2015) Mobile DNA in the Pathogenic Neisseria. Microbiol Spectr 3:MDNA3-0015-2014|
|Zhang, Yan; Rajan, Rakhi; Seifert, H Steven et al. (2015) DNase H Activity of Neisseria meningitidis Cas9. Mol Cell 60:242-55|
|Gault, Joseph; Ferber, Mathias; Machata, Silke et al. (2015) Neisseria meningitidis Type IV Pili Composed of Sequence Invariable Pilins Are Masked by Multisite Glycosylation. PLoS Pathog 11:e1005162|
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