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.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Method to Extend Research in Time (MERIT) Award (R37)
Project #
5R37AI033493-22
Application #
8792357
Study Section
Bacterial Pathogenesis Study Section (BACP)
Program Officer
Hiltke, Thomas J
Project Start
1994-05-01
Project End
2018-01-31
Budget Start
2015-02-01
Budget End
2016-01-31
Support Year
22
Fiscal Year
2015
Total Cost
$386,250
Indirect Cost
$136,250
Name
Northwestern University at Chicago
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
005436803
City
Chicago
State
IL
Country
United States
Zip Code
60611
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Quillin, Sarah J; Hockenberry, Adam J; Jewett, Michael C et al. (2018) Neisseria gonorrhoeae Exposed to Sublethal Levels of Hydrogen Peroxide Mounts a Complex Transcriptional Response. mSystems 3:
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Palmer, Guy H; Bankhead, Troy; Seifert, H Steven (2016) Antigenic Variation in Bacterial Pathogens. Microbiol Spectr 4:

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