Diabetes mellitus is a complex disease in which the primary clinical symptom is abnormally high levels of plasma glucose. It may affect up to 5% of the human population. The major regulatory hormones that control glucose homeostasis are insulin and glucagon. Both hormones are expressed only in islet cells of the pancreas. In order to understand why insulin genes are only expressed in islet cells, it is necessary to develop a cell-free system to identify all the necessary components required for the expression of this important gene. Once these components are identified, one can then study their mechanism of action. In this proposal, we design experiments to identify, isolate and study the mechanism of action of transcription factors required for the expression of the insulin gene. These studies will involve various aspects of biochemistry, protein chemistry, molecular biology, some immunology and some physiology. It is expected that the results derived from this project will be relevant to the better understanding of the insulin gene regulation. In addition, the following proposal should also be pertinent in elucidating a more precise hypothesis for the regulation of gene expression during differentiation, development and cancer metastasis.