Genomic DNA polypyrimidine tracts

This entry refers to genomic DNA sequences rich in cytosine and thymine (polypyrimidine tracts) that share partial sequence homology with the regulatory nuclease hypersensitive element (NHE) of the KRAS gene (Cogoi et al., 2010) [1]. These tracts are distributed throughout the human genome and are capable of forming triple-helical (triplex) DNA structures. In the development of antigene therapies, such as triplex-forming oligonucleotides (TFOs) designed to silence KRAS expression, these homologous sequences represent significant off-target binding sites (Xodo, 2014) [2]. Binding to these unintended locations can lead to the transcriptional interference of non-target genes, potentially resulting in adverse effects or reduced therapeutic potency due to drug sequestration (Cogoi et al., 2014) [3]. Consequently, these sequences are not therapeutic targets themselves but are critical parameters in the specificity and safety assessment of KRAS-targeted nucleic acid drugs. Identifying and minimizing interactions with these tracts is a primary challenge in the design of highly selective genomic medicines for cancer (Xodo, 2014) [2]. Understanding the distribution and accessibility of these tracts across the genome is vital for improving the therapeutic index of KRAS-directed agents.

Other names

Off-target genomic DNAHomologous polypyrimidine sequencesKRAS-homologous DNA tractsGenomic DNA: other polypyrimidine tracts with partial homology to the KRAS-targeted sequence

Off-target hybridization and triplex formation at homologous genomic sites, leading to unintended transcriptional interference.