G-quadruplex stabilization in the ions and maltose transporters inhibitSalmonella entericagrowth and virulence

Abstract

AbstractThe G-quadruplex structure forming motifs have recently emerged as a novel therapeutic drug target in various human pathogens. Herein, we report three highly conserved G-quadruplex motifs (SE-PGQ-1, 2, and3) in genome of all the 412 strains ofSalmonella enterica. Bioinformatics analysis inferred the presence of SE-PGQ-1 in the regulatory region ofmgtA, presence of SE-PGQ-2 in the open reading frame ofentAand presence of SE-PGQ-3 in the promoter region ofmalEandmalKgenes. The products ofmgtAandentAare involved in transport and homeostasis of Mg2+and Fe3+ion and thereby required for bacterial survival in the presence of reactive nitrogen/oxygen species produced by the host macrophages, whereas,malKandmalEgenes are involved in transport of maltose sugar, that is one of the major carbon source in the gastrointestinal tract of human. The formation of stable intramolecular G-quadruplex structures by SE-PGQs was confirmed by employing CD, EMSA and NMR spectroscopy. Cellular studies revealed the inhibitory effect of 9-amino acridine onSalmonella entericagrowth. Next, CD melting analysis demonstrated the stabilizing effect of 9-amino acridine on SE-PGQs. Further, polymerase inhibition and RT-qPCR assays emphasize the biological relevance of predicted G-quadruplex in the expression of PGQ possessing genes and demonstrate the G-quadruplexes as a potential drug target for the devolping novel therapeutics for combatingSalmonella enterica infection.Author SummarySince last several decades’ scientific community has witnessed a rapid increase in number of such human pathogenic bacterial species that acquired resistant to multiple antibacterial agents. Currently, emergence of multidrug-resistant strains remain a major public health concern for clinical investigators that rings a global alarm to search for novel and highly conserved drug targets. Recently, G-quadruplex structure forming nucleic acid sequences were endorsed as highly conserved Drug target for preventing infection of several human pathogens including viral and protozoan species. Therefore, here we explored the presence G-quadruplex forming motif in genome ofSalmonella entericabacteria that causes food poisoning, and enteric fever in human. The formation of intra molecular G-quadruplex structure in four genes (mgtA,entA,malEandmalK) was confirmed by NMR, CD and EMSA. The 9-amino acridine, a known G-quadruplex binder has been shown to stabilize the predicted G-quadruplex motif and decreases the expressioin of G-quadruplex hourbouring genes using RT-PCR and cellular toxicity assay. This study concludes the presence of G-quadruplex motifs in essential genes ofSalmonella entericagenome as a novel and conserved drug target and 9-amino acridine as candidate small molecule for preventing the infection ofSalmonella entericausing a G4 mediated inhibition mechanism.