Genomic sites hypersensitive to ultraviolet radiation

Area of Science:

• Genomics
• Molecular Biology
• Cancer Research

Background:

• The genome may contain outlier sequences highly sensitive to environmental agents, potentially serving as biomarkers for carcinogen exposure.
• These sensitive sites could influence cell physiology directly, rather than solely through rare mutations.

Purpose of the Study:

• To develop and apply novel methods for quantifying rare DNA lesions at single-base resolution across the genome.
• To investigate the prevalence and characteristics of UV-induced DNA damage in different human cell types.

Main Methods:

• Utilized new statistical methods, adductSeq and freqSeq, for high-resolution quantification of DNA lesions.
• Analyzed DNA damage patterns in primary human melanocytes and fibroblasts following UV exposure.

Main Results:

• Identified specific genomic regions ('hyperhotspots') that acquire UV-induced cyclobutane pyrimidine dimers (CPDs) at much higher rates than average.
• Found hyperhotspots to be more prevalent in melanocytes and disproportionately located near genes, including those involved in RNA binding and transcription factor binding sites.
• Discovered a motif (A2-15TTCTY) that accumulates CPDs slowly, repairs them inefficiently, and exhibits 'dark CPDs' post-UV exposure.

Conclusions:

• Melanocyte CPD hyperhotspots correlate with known UV signature mutations in melanoma promoters and cancer drivers, suggesting a role in tumor evolution.
• UV exposure at sunburn levels can induce hyperhotspot CPDs in critical cellular pathways, potentially creating phenome instability and promoting mutations.
• Hyperhotspots may function as epigenetic marks that drive genomic instability and facilitate the selection of weak cancer drivers.