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.

Public Health Relevance

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.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Method to Extend Research in Time (MERIT) Award (R37)
Project #
Application #
Study Section
Bacterial Pathogenesis Study Section (BACP)
Program Officer
Hiltke, Thomas J
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Northwestern University at Chicago
Schools of Medicine
United States
Zip Code
Anderson, Mark T; Dewenter, Lena; Maier, Berenike et al. (2014) Seminal plasma initiates a Neisseria gonorrhoeae transmission state. MBio 5:e01004-13
Chen, Adrienne; Seifert, H Steven (2014) Saturating mutagenesis of an essential gene: a majority of the Neisseria gonorrhoeae major outer membrane porin (PorB) is mutable. J Bacteriol 196:540-7
Chen, Adrienne; Seifert, H Steven (2013) Structure-function studies of the Neisseria gonorrhoeae major outer membrane porin. Infect Immun 81:4383-91
Anderson, Mark T; Seifert, H Steven (2013) Phase variation leads to the misidentification of a Neisseria gonorrhoeae virulence gene. PLoS One 8:e72183
Cahoon, Laty A; Manthei, Kelly A; Rotman, Ella et al. (2013) Neisseria gonorrhoeae RecQ helicase HRDC domains are essential for efficient binding and unwinding of the pilE guanine quartet structure required for pilin antigenic variation. J Bacteriol 195:2255-61
Cahoon, Laty A; Seifert, H Steven (2013) Transcription of a cis-acting, noncoding, small RNA is required for pilin antigenic variation in Neisseria gonorrhoeae. PLoS Pathog 9:e1003074
Stohl, Elizabeth A; Dale, Erin M; Criss, Alison K et al. (2013) Neisseria gonorrhoeae metalloprotease NGO1686 is required for full piliation, and piliation is required for resistance to H2O2- and neutrophil-mediated killing. MBio 4:
Stohl, Elizabeth A; Chan, Yolande A; Hackett, Kathleen T et al. (2012) Neisseria gonorrhoeae virulence factor NG1686 is a bifunctional M23B family metallopeptidase that influences resistance to hydrogen peroxide and colony morphology. J Biol Chem 287:11222-33
Criss, Alison K; Seifert, H Steven (2012) A bacterial siren song: intimate interactions between Neisseria and neutrophils. Nat Rev Microbiol 10:178-90
Cahoon, Laty A; Seifert, H Steven (2011) Focusing homologous recombination: pilin antigenic variation in the pathogenic Neisseria. Mol Microbiol 81:1136-43

Showing the most recent 10 out of 43 publications