Genetic Interactions of DNA Repair Pathways in the PathogenNeisseria meningitidis

Abstract

The current increase in the incidence and severity of infectious diseases mandates improved understanding of the basic biology and DNA repair profiles of virulent microbes. In our studies of the major pathogen and model organism Neisseria meningitidis, we constructed a panel of mutants inactivating genes involved in base excision repair, mismatch repair, nucleotide excision repair (NER), translesion synthesis, and recombinational repair pathways. The highest spontaneous mutation frequency among the N. meningitidis single mutants was found in the MutY-deficient strain as opposed to mutS mutants in Escherichia coli, indicating a role for meningococcal MutY in antibiotic resistance development. Recombinational repair was recognized as a major pathway counteracting methyl methanesulfonate-induced alkylation damage in the N. meningitidis. In contrast to what has been shown in other species, meningococcal NER did not contribute significantly to repair of alkylation-induced DNA damage, and meningococcal recombinational repair may thus be one of the main pathways for removal of abasic (apurinic/apyrimidinic) sites and strand breaks in DNA. Conversely, NER was identified as the main meningococcal defense pathway against UV-induced DNA damage. N. meningitidis RecA single mutants exhibited only a moderate decrease in survival after UV exposure as opposed to E. coli recA strains, which are extremely UV sensitive, possibly reflecting the lack of a meningococcal SOS response. In conclusion, distinct differences between N. meningitidis and established DNA repair characteristics in E. coli and other species were identified.Neisseria meningitidis, or the meningococcus (MC), is a gram-negative inhabitant of the human oropharynx that may disseminate into the bloodstream and traverse the blood-brain barrier to cause septicemia and/or meningitis. MC cells residing on mucosal surfaces are exposed to DNA damaging agents, in particular, reactive oxygen species (ROS) generated from normal cellular metabolism or a highly effective immune system through the oxidative burst. ROS from exogenous and endogenous sources can induce a vast number of different types of DNA damage, including single-and double-strand breaks, abasic (apurinic/apyrimidinic, or AP) sites, and base damages, among which the oxidation product of guanine, 7,8-dihydro-8-oxo-2Ј-deoxyguanosine (8oxoG), is one of the most frequent (13). Oxidative DNA damage is primarily processed by the base excision repair (BER) pathway (52). In Escherichia coli, BER is initiated by DNA glycosylases that nick the Nglycosylic bond and remove the damaged base by a flipping mechanism. The remaining sugar and phosphate moieties are subsequently excised either by an AP-lyase activity inherent in many DNA glycosylases or by an AP endonuclease, leaving the processing of the 3Ј or 5Ј terminus, respectively, to a deoxyribose phosphodiesterase (52). A triplet of enzymes referred to as the GO system composed of the DNA glycosylases MutY and Fpg, as well as the nucleotide hydrolase MutT, is involved in ...

Genetic Characterization of the Nucleotide Excision Repair System of Neisseria gonorrhoeae

“…Thus, the effect of lowering RecA expression in wild-type cells or uvrABC mutants has a relatively minor effect on UV survival. This is similar to the effect reported by Davidsen et al in a uvrA recA6 double mutant from the related human pathogen Neisseria meningitidis (11). Intriguingly, we observed a large increase in UV sensitivity in the mfd mutant in the absence of RecA expression.…”

“…In 1997, Black et al demonstrated that the Gc uvrA gene could complement an E. coli uvrA mutant for UV survival (3), and in 1995 the same group demonstrated that a uvrB mutant was deficient in UV survival (4). Finally, Davidsen et al demonstrated that a Neisseria meningitidis uvrA mutant was also deficient for UV survival but not altered for survival to alkylating agents (11). The involvement of NER in other DNA recombination and repair pathways in pathogenic Neisseria, such as natural competence, repair of spontaneous mutations, and pilus variations, has not been defined.…”

Mismatch Correction Modulates Mutation Frequency and Pilus Phase and Antigenic Variation in Neisseria gonorrhoeae

“…In E. coli, MMC mutants exhibit a striking increase in the frequency of spontaneous mutation to antibiotic resistance (reviewed in reference 3), whereas the increase in mutation frequency to Nal r in MMCdeficient Gc was only 4-to 5-fold above the parental strain. This observation is in agreement with the effects of MMC inactivation in N. meningitidis (7,26,38). While in E. coli uvrD (also termed mutU) and mutS/L mutants have similar effects on spontaneous mutation (28), in Gc the mutation frequency in uvrD MMC double mutants is significantly higher than any single mutant.…”

“…2). Similar low increases in the frequency of spontaneous mutation have previously been reported for mutS and mutL mutants in N. meningitidis (7,26,38). Therefore, mutS and mutL are functional MMC genes in Gc and have modest effects on the correction of point mutations in this organism.…”

DprA is required for natural transformation and affects pilin variation in Neisseria gonorrhoeae

“…Previous studies have shown that UV-induced DNA damage is repaired mostly by nucleotide excision repair in N. meningitidis (Davidsen et al, 2007). However, cells lacking RecA .…”