G-quadruplex stabilization in the ions and maltose transporters inhibit Salmonella enterica growth and virulence

Neha Jain; Subodh Kumar Mishra; Uma Shankar; Arpita Tawani; Ankit Jaiswal; Tarun Kumar Sharma; Prashant Kodgire; Amit Kumar

Bioinformatics sequence analysis revealed the presence of three SE-PGQs (SE-PGQ 1-3) in three different gene locations of S. enterica genome. The SE-PGQ-1 was found to be present in the regulatory region of mgtA, SE-PGQ-2 in the open reading frame of entA, whereas SE-PGQ-3 found to lie in the regulatory region of malK and malE genes (Fig 3a) . In order to confirm the formation of G-quadruplex structure by SE-PGQs, Circular Dichroism spectroscopy (CD), gel mobility shift assay (EMSA) and one dimensional 1 H NMR spectroscopy were employed. Further to validate these SE-PGQ as a potential drug target, CD melting, and Taq polymerase stop assay were performed that confirmed 9-amino-acridine, a known G4 binding molecule interact and stabilizes the SE-PGQs motifs with high affinity and selectivity over the duplex DNA. Disc diffusion assay and MTT cytotoxicity assay confirmed the growth inhibition of S. enterica cells by 9-amino acridine molecule. Further, Real-time -quantitative PCR (RT-qPCR) revealed the reduced expression of genes that harbor the SE-PGQs in either their coding region or regulatory region upon the treatment with 9-amino acridine. This change in the expression of PGQs harboring gene in the presence of G4 binding ligand suggested a G4 mediated regulatory mechanism in the expression of these genes.