G-quadruplexes (G4s) are non-canonical secondary structures of DNA that are prevalent within the human genome. In the last 30 years, advances in genomics, bioinformatics and imaging have unravelled
various biological roles of G4s, including regulation of gene expression, translation, and replication. Most of the tools currently available to investigate G4-biology rely on small molecule ligands that stabilise these structures. However, the development of probes that disrupt G4s is equally important to study their biology, given the body of evidence suggesting that the uncontrolled cellular accumulation
of G4s is associated with neurodegenerative diseases and accelerated ageing. In this thesis, a suite of biophysical, biochemical, and cellular approaches was used to systematically investigate how efficient disruption of G4s can be achieved by using Locked Nucleic Acids (LNA)-modified oligonucleotides as
invader probes. The data generated through these investigations revealed that the strategic positioning of LNA-modifications within oligonucleotide sequences complementary to G4s can significantly accelerate the kinetics of G4-disruption, compared to unmodified oligonucleotides. Furthermore, it was
demonstrated that LNA-modifications can be leveraged to design oligonucleotide probes as short as 10 nucleotides, which were found to be efficient at disrupting G4s under physiological conditions. These observations were consistent across two distinct G4 systems. The application of the designed LNA modified G4-disrupting probes in a reporter-based cellular assay revealed that disrupting a specific G4
located in the promoter region of the oncogene c-KIT results in significantly increased gene-expression levels. Collectively, these suggest that strategically designed LNA-modified oligonucleotide probes are
accessible chemical biology tools that could be used by the wider scientific community to interrogate the biology associated with the disruption of specific G4s in the human genome and may in the future be leveraged to develop G4-targeting therapeutics.