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Abstract H-DNA is an intramolecular DNA triplex formed by homopurine-homopyrimidine mirror repeats. Since its discovery, the field has advanced from characterizing the structure in vitro to discovering its existence and role in vivo. H-DNA interacts with cellular machinery in unique ways, stalling DNA and RNA polymerases and causing genome. The foundational S1 nuclease and chemical probing technologies originally used to show H-DNA formation have been updated and combined with genome-wide sequencing methods for large-scale mapping of secondary structures. There is evidence for triplex H-DNA’s role in polycystic kidney disease, cancer, and numerous repeat expansion diseases. In polycystic kidney disease (PKD), an H-DNA forming repeat region within the PKD1 gene stalls DNA replication and induces fragility. H-DNA- forming repeats in various genes have a role in cancer; the most well-studied examples involve H-DNA-mediated fragility causing translocations in multiple lymphomas. Lastly, H-DNA-forming repeats have been implicated in four repeat expansion diseases: Friedreich's ataxia (FRDA), GAA-FGF14-related ataxia, X-linked Dystonia Parkinsonism (XDP), and cerebellar ataxia, neuropathy and vestibular areflexia syndrome (CANVAS). In this review, we summarize H-DNA’s discovery and characterization, evidence for its existence and function in vivo, and the field's current knowledge on its role in physiology and pathology.
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The role of fork stalling and DNA structures in causing chromosome fragility
Abstract Alternative non‐B form DNA structures, also called secondary structures, can form in certain DNA sequences under conditions that produce single‐stranded DNA, such as during replication, transcription, and repair. Direct links between secondary structure formation, replication fork stalling, and genomic instability have been found for many repeated DNA sequences that cause disease when they expand. Common fragile sites (CFSs) are known to be AT‐rich and break under replication stress, yet the molecular basis for their fragility is still being investigated. Over the past several years, new evidence has linked both the formation of secondary structures and transcription to fork stalling and fragility of CFSs. How these two events may synergize to cause fragility and the role of nuclease cleavage at secondary structures in rare and CFSs are discussed here. We also highlight evidence for a new hypothesis that secondary structures at CFSs not only initiate fragility but also inhibit healing, resulting in their characteristic appearance.
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- Award ID(s):
- 1817499
- PAR ID:
- 10370798
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Genes, Chromosomes and Cancer
- Volume:
- 58
- Issue:
- 5
- ISSN:
- 1045-2257
- Page Range / eLocation ID:
- p. 270-283
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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