CORNEAL-EPITHELIAL NUCLEAR FERRITIN AND U.V. PROTECTION

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DESCRIPTION: Ultraviolet (UV) light constitutes a major environmental insult to all exposed tissues of the body, including those comprising the cornea and other underlying ocular structures. UV-light can damage a wide variety of macromolecular components including DNA resulting, for example, in cancer. This damage can be direct, or it can be indirect through the generation of reactive oxygen species (ROS). Corneal epithelial (CE) cells, however, seem to be refractory to such damage. Cancers of these cells are rare, even though this tissue is transparent and exposed to mutagenic UV light and other sources of ROS. Previous studies suggest that one mechanism that CE cells have evolved to prevent damage to their DNA involves ferritin in a nuclear localization. This molecule seems to greatly diminish the effects of UV-produced ROS to DNA-most likely by sequestering free iron, which acts as a catalyst in generating hydroxyl radicals, the most damaging ROS. Other studies suggest that the nuclear localization of ferritin is effected by a nuclear transporter, which is termed "ferritoid". Ferritoid is comprised of two regions, one, which contains a nuclear localization signal (NLS) and is responsible for the nuclear transport, and another, which is involved in the binding to ferritin, which ferritoid subsequently carries into the nucleus. The mechanism of this interaction between ferritoid and ferritin, and the subsequent nuclear transport will be examined further. The fate of ferritoid following transport and whether phosphorylation is involved in regulating the transport will also be investigated. The mechanisms responsible for regulating the production of ferritin and ferritoid will also be examined. The studies will include whether the synthesis of these molecules is co-ordinate with one another and whether the synthesis of ferritin involves a unique type of translational regulation, which results in a low iron ferritin. Such a low iron ferritin may be highly efficient at iron sequestration and therefore protection against active ROS. For the synthesis of ferritoid, studies will involve whether "stress response elements" in the gene respond to ROS. Lastly, it will be determined whether the protection against damage by ROS provided by nuclear ferritin in CE-cells, can be afforded to other cell types in which ROS potentially have deleterious effects