The development of nanotechnology has allowed the identification of unique properties in nanomaterials that have, in turn, led to the development of commercial applications in many fields, such as chemical catalysis, semiconductors, water purification, cosmetics, microelectrodes, biosensors, the food industry, biomedicine, etc. In 2009, developers generated more than $1 billion from the sale of nanomaterials, and the market for nanotechnology is expected to grow to 75.8 billion by 2020 with several hundreds of thousands of jobs. Thus the levels of human exposure to anthropogenic nanoparticles will substantially increase. As an important transition metal, nickel nanoparticles (Nano-Ni) have wide ranging applications in the fields of batteries, electrical conductors, permanent magnets, magnetic fluids, magnetic recording media, solar energy absorption, fuel cell electrodes, and catalysts. In addition, due to structural and inherent chemical and physical properties, nickel alloy nanomaterials have received special interest in biomedical applications. In this proposal, we selected Nano-Ni as a model metal nanoparticle because of its wide industrial interest and biological and medical applications. Based on our preliminary data, our working hypothesis is that Nano-Ni can cause oxidative stress and DNA damage in lung epithelial cells, and long-term exposure to Nano- Ni results in DNA repair deficiency by down-regulating Rad52, increased genomic instability and cell transformation through up-regulation of miR-210, and nuclear accumulation of the hypoxia inducible factor 1? (HIF-1?). The following two Specific Aims will be pursued. Specific Aim 1. Examine the role of HIF-1? pathway in Nano-Ni-induced genotoxic effects in vitro and in vivo. We will first examine whether exposure to Nano-Ni will induce DNA damage in normal human lung epithelial cells BEAS-2B and in mice by measuring the phosphorylation level of ataxia telangiectasia mutated (ATM) at Ser1981 and p53 at Ser15, and expression level of Rad52 and phosphorylated histone H2AX (?-H2AX). We will then investigate the role of HIF-1? in Nano-Ni-induced DNA damage by using: (1) HIF-1? - specific siRNA; and (2) HIF-1? knock-out cells. Specific Aim 2. Examine whether exposure to Nano-Ni causes down-regulation of Rad52 through up-regulation of miR-210 induced by HIF-1? activation during Nano-Ni-induced cell transformation. We will first determine whether long-term exposure to low doses of Nano-Ni will induce normal BEAS-2B cells to transform. We will then measure the levels of Rad52, miR-210 and HIF-1? in cells with long-term exposure to Nano-Ni and in Nano-Ni-transformed cells. Finally, we will explore the role of Rad52 in Nano-Ni-induced cell transformation through overexpression or knockout of Rad52.