An Alternative DNA Structure Is Necessary for Pilin Antigenic Variation in Neisseria gonorrhoeae
Laty A. Cahoon and
H. Steven Seifert*
Pathogens can use DNA recombination to promote antigenic variation
(Av) of surface structures to avoid immune detection. We identified
a cis-acting DNA sequence near the antigenically variable pilin
locus of the human pathogen,
Neisseria gonorrhoeae. This 16–base
pair guanine (G)–rich sequence was required for pilin
Av and formed a guanine quartet (G4) structure in vitro. Individual
mutations that disrupted the structure also blocked pilin Av
and prevented nicks required for recombination from occurring
within the G4 region. A compound that binds and stabilizes G4
structures also inhibited pilin Av and prevented nicks from
occurring on the G-rich strand. This site constitutes a recombination
initiation sequence/structure that directs gene conversion to
a specific chromosomal locus.
* To whom correspondence should be addressed. E-mail: h-seifert{at}northwestern.edu
