Genome wide mapping of G-Quadruplex motifs affecting gene expression in pathogenic bacteria

Abstract

G-quadruplexes (GQs) are one of the most extensively researched non-canonical secondary structures of nucleic acids and are ubiquitously present in all species from viruses to prokaryotes and eukaryotes. GQs are formed by staking of more than one G-tetrads, and each G-tetrad is made by non-canonical reciprocal interaction of Guanine residues arrayed in a plane. The cyclic guanine arrangement is formed due to Hoogsteen and Watson–Crick hydrogen bonding. The GQ structure can be formed by an intra or intermolecular interaction between different strands and are stabilized by monovalent cations. They are located in the promoters, coding, and non-coding regions of the genomic DNA or RNA. The GQ structure in promoters and UTRs has been extensively reported, reinforcing their importance as transcription and translation regulators in various cancers and neurological disorders. The telomeric region of the chromosomal ends in the vertebrates, trypanosomes, and fungi have the repeat sequence of TTAGGG. For maintaining the telomeric repeats, cells possess a special enzyme called ‘Telomerase’. Normal cells divide in limit before reaching senescence due to under expression of telomerase. This phenomenon is known as Hayflick limit which is defined by the length of the chromosomal ends known as telomeres. But in cancerous cells, telomerase enzyme is produced extensively which abolishes the Hayflick limit and keep these cells to divide endlessly. These telomeric repeats have a high propensity to form GQ structures.