| Autor: |
Savitskaya VY; Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia., Strekalovskikh VV; Department of Bioengineering and Bioinformatics, Lomonosov Moscow State University, 119991 Moscow, Russia., Snyga VG; Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia., Monakhova MV; Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia., Arutyunyan AM; Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia., Dolinnaya NG; Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia., Kubareva EA; Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia. |
| Abstrakt: |
The human pathogen Neisseria gonorrhoeae uses a homologous recombination to undergo antigenic variation and avoid an immune response. The surface protein pilin (PilE) is one of the targets for antigenic variation that can be regulated by N. gonorrhoeae mismatch repair (MMR) and a G-quadruplex (G4) located upstream of the pilE promoter. Using bioinformatics tools, we found a correlation between pilE variability and deletion of DNA regions encoding ngMutS or ngMutL proteins, the main participants in N. gonorrhoeae methyl-independent MMR. To understand whether the G4 structure could affect the ngMutL-mediated regulation of pilin antigenic variation, we designed several synthetic pilE G4-containing oligonucleotides, differing in length, and related DNA duplexes. Using CD measurements and biochemical approaches, we have showed that (i) ngMutL preferentially binds to pilE G4 compared to DNA duplex, although the latter is a cognate substrate for ngMutL endonuclease, (ii) protein binding affinity decreases with shortening of quadruplex-containing and duplex ligands, (iii) the G4 structure inhibits ngMutL-induced DNA nicking and modulates cleavage positions; the enzyme does not cleave DNA within G4, but is able to bypass this noncanonical structure. Thus, pilE G4 may regulate the efficiency of pilin antigenic variation by quadruplex binding to ngMutL and suppression of homologous recombination. |
