Chronic sun exposure is associated with distinct histone acetylation changes in human skin

Photoaging is premature aging of the skin caused by sunlight or artificial UV exposure (e.g. tanning beds). It affects almost everyone in the world. Histones are proteins which are positively charged, allowing them to associate with DNA, which is negatively charged. Some histones are like spools for the thread‐like DNA to wrap around. This study, from China, aimed to analyse patterns of changes (modification) to histones, which can regulate gene expression in sun‐exposed and non‐exposed skin, and identify photoaging‐related genes modified by abnormal histones. We tested the histone modification profile in sun‐exposed and non‐exposed skin samples with ELISA (a test that uses antibodies and color change to identify a substance), and found that the level of histone H3 acetylation (a kind of histone modification) increased significantly in sun‐exposed skin samples compared with non‐exposed ones. The increased P300 and decreased HDAC1 and SIRT1 expression in sun‐exposed skin might be the main cause (P300, HDAC1 and SIRT1 are enzymes related to histone modification). Further, tests were performed to screen the genes whose histone H3 acetylation changed in sun‐exposed skin samples and non‐exposed ones. We found that 227 genes displayed significant hyperacetylation (simply put, over‐modification) of histone H3, and 81 genes displayed significant hypoacetylation (under‐modification) of histone H3 in sun‐exposed skin samples compared with non‐exposed ones. In summary, histone H3 hyperacetylation caused by chronic sun exposure may play a critical role in the development of skin photoaging.