Higher than normal rates of cancer, heart disease, Alzheimer's, male infertility and diabetes are linked to a class of proteins that contain the essential trace element selenium. These so-called “selenoproteins” possess the unique amino acid, selenocysteine, which is universally required for the antioxidant, synthetic or protein folding functions found in this class. The majority of selenoproteins function as the primary defense mechanism against oxidative cellular damage and transformation, thus making the synthesis and regulation of these proteins an essential area of research. Since selenocysteine is incorporated at specific UGA codons, which usually signal translation termination, a fundamental redefinition of the genetic code must occur. Our lab is studying many different facets of the conundrum presented by the selenocysteine incorporation process. One of the ultimate goals for our research is to be able to specifically regulate the expression of potentially beneficial selenoproteins in vivo. In order to achieve this goal, we must understand all of the factors that contribute not only to the basic selenocysteine incorporation reaction but also to the regulation of this process. We have recently adopted a zebrafish animal model to study the regulatory networks that link oxidative stress to selenoprotein synthesis. Recent data in this system reinforces a known link between one of the selenocysteine incorporation factors and lung cancer prevalence. We are now engaging in a multi-pronged approach to uncover the mechanistic aspects of this link.