It is becoming increasingly clear that post-translational modifications of DNA and proteins play an important role in human health and many disease states. Within FY2000 we have extended our studies on the impact of DNA methylation on human cancers. Using a combination of human tumor samples and in vitro biochemistry and molecular biology we have ascertained the methylation status on the promoter for the human hereditary breast and ovarian cancer susceptibility gene, BRCA-1. These studies revealed a critical requirement for the cyclic- AMP response element binding (CREB) protein in the transcription of this gene. This is particularly interesting given the intense interest in a protein that binds CREB known as CREB binding protein or CBP and its ability to acetylate histones and the tumor suppressor gene p53. We are currently exploring the mechanisms by which p53 may influence glucocorticoid receptor activation of transcription. As models we are using recently developed human osteosacoma cells that lack p53 in comparison to cells that retain wild type p53.Additional experiments have described the transcriptional mechanisms that underlie the estrogen receptor dependent activation of the Cathepsin D gene in human breast cancer cells. In addition we have begun to explore the specific contributions made by the two distinct isoforms of the estrogen receptor in collaboration with the Korach group. The continued evaluation of these and additional novel human genetic systems will provide the underpinning of our efforts to define a molecular map of the hormone dependent changes that occur in human cells. This will be critical for an enhanced understanding the impact of environmental endocrine disruptors on human health.