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Gu Can*, Huang Jinhua, Yang Shengbo. *Xiangya Medical College, Central South University, Changsha 410013, China Corresponding author��Yang Shengbo, Email: szyangsb@163.com ��Abstract�� DNA methylation, which refers to a chemical modification process in which a methyl group is covalently binding to the 5-position of the cytosine ring in CpG dinucleotides to form 5-methylcytosine under the catalysis by DNA methyltransferases ��DNMTs��, is a key epigenetic modification for gene regulation and mutation. Recent studies have shown that aberrant DNA methylation patterns exist in photoaged skin and ultraviolet radiation-induced skin tumors, which may be caused by decreased expression and activity of DNMT1, base excision repair and nucleotide excision repair, growth arrest, DNA-damage-inducible protein 45 alpha ��Gadd45a��-mediated DNA demethylation, and so on.