# Non-B DNA structures and their contributions to genetic diversity, aging, and disease

## TL;DR

This paper explores how alternative DNA structures contribute to genetic diversity, disease, and aging by affecting genome stability and function.

## Contribution

The paper provides a comprehensive overview of recent advances in understanding the biological roles and consequences of non-B DNA structures.

## Key findings

- Non-B DNA structures are enriched in functional genomic regions and are linked to gene regulation and genome instability.
- These structures contribute to replication stress, transcription stalling, and DNA breaks, leading to mutational hotspots.
- Non-B DNA structures play a dual role in promoting genetic variation and contributing to mutations in aging and disease.

## Abstract

DNA is most often found in its canonical B-form double-helical structure, but can also adopt alternative conformations, known as non-B DNA structures. Numerous non-B structures have been characterized, including G-quadruplexes, i-motifs, Z-DNA, hairpins, cruciforms, slipped structures, R-loops, and H-DNA. Non-B DNA motifs are enriched in functional regions, including near transcription start and end sites, topologically associated domains, and replication origins, suggesting their importance in gene regulation, genome organization, and replication. However, these structures are intrinsically prone to error-generating processing, leading to genomic instability and hence have been implicated in the development of human diseases. Here, we discuss recent advances in understanding the biological roles of non-B DNA structures and their contribution to genomic instability in somatic and germline contexts. We highlight how they promote replication stress, transcription stalling, and DNA breaks, resulting in the formation of mutational hotspots. Emerging technologies have enabled the detailed mapping of previously challenging repetitive regions that harbor potential non-B DNA-forming sequences, and are poised to unravel additional contributions in human disease and evolution. Furthermore, we explore the dual role of non-B DNA as a driver of genetic variation that facilitates evolutionary adaptation and as a source of mutations that contribute to tissue dysfunction and aging.

Graphical Abstract