MicroRNAs in skin response to UV radiation.

Solar ultraviolet (UV) radiation, an ubiquitous environmental carcinogen, is classified depending on the wavelength, into three regions; short-wave UVC (200-280 nm), mid-wave UVB (280-320 nm), and long-wave UVA (320- 400 nm). The human skin, constantly exposed to UV radiation, particularly the UVB and UVA components, is vulnerable to its various deleterious effects such as erythema, photoaging, immunosuppression and cancer. To counteract these and for the maintenance of genomic integrity, cells have developed several protective mechanisms including DNA repair, cell cycle arrest and apoptosis. The network of damage sensors, signal transducers, mediators, and various effector proteins is regulated through changes in gene expression. MicroRNAs (miRNAs), a group of small non-coding RNAs, act as posttranscriptional regulators through binding to complementary sequences in the 3´-untranslated region of their target genes, resulting in either translational repression or target degradation. Recent studies show that miRNAs add an additional layer of complexity to the intricately controlled cellular responses to UV radiation. This review summarizes our current knowledge of the role of miRNAs in the regulation of the human skin response upon exposure to UV radiation.