Roles of non-canonical structures of nucleic acids in cancer and neurodegenerative diseases

Cancer and neurodegenerative diseases are caused by genetic and environmental factors. Expression of tumour suppressor genes is suppressed by mutations or epigenetic silencing, whereas for neurodegenerative disease-related genes, nucleic acid-based effects may be presented through loss of protein function due to erroneous protein sequences or gain of toxic function from extended repeat transcripts or toxic peptide production. These diseases are triggered by damaged genes and proteins due to lifestyle and exposure to radiation. Recent studies have indicated that transient, non-canonical structural changes in nucleic acids in response to the environment can regulate the expression of disease-related genes. Non-canonical structures are involved in many cellular functions, such as regulation of gene expression through transcription and translation, epigenetic regulation of chromatin, and DNA recombination. Transcripts generated from repeat sequences of neurodegenerative disease-related genes form non-canonical structures that are involved in protein transport and toxic aggregate formation. Intracellular phase separation promotes transcription and protein assembly, which are controlled by the nucleic acid structure and can influence cancer and neurodegenerative disease progression. These findings may aid in elucidating the underlying disease mechanisms. Here, we review the influence of non-canonical nucleic acid structures in disease-related genes on disease onset and progression.