The m⁶A reader YTHDC2 regulates UVB-induced DNA damage repair and histone modification

Ultraviolet B (UVB) radiation represents a major carcinogen for the development of all skin cancer types. Mechanistically, UVB induces damage to DNA in the form of lesions, including cyclobutane pyrimidine dimers (CPDs). Disruption of the functional repair processes, such as nucleotide excision repair (NER), allows persistence of DNA damage and contributes to skin carcinogenesis. Recent work has implicated m⁶A RNA methylation and its regulatory proteins as having critical roles in facilitating UVB-induced DNA damage repair. However, the biological functions of the m⁶A reader YTHDC2 are unknown in this context. Here, we show that YTHDC2 inhibition enhances the repair of UVB-induced DNA damage. We discovered that YTHDC2 inhibition increased the expression of PTEN while it decreased the expression of the PRC2 component SUZ12 and the levels of the histone modification H3K27me3. However, none of these functions were causally linked to the improvements in DNA repair, suggesting that the mechanism utilized by YTHDC2 may be unconventional. Moreover, inhibition of the m⁶A writer METTL14 reversed the effect of YTHDC2 inhibition on DNA repair while inhibition of the m⁶A eraser FTO mimicked the effect of YTHDC2 inhibition, indicating that YTHDC2 may regulate DNA repair through the m⁶A pathway. Finally, compared to normal human skin, YTHDC2 expression was upregulated in human cutaneous squamous cell carcinomas (cSCC), suggesting that it may function as a tumor-promoting factor in skin cancer. Taken together, our findings demonstrate that the m⁶A reader YTHDC2 plays a role in regulating UVB-induced DNA damage repair and may serve as a potential biomarker in cSCC.