Understanding the molecular logic of regulatory and epigenetic strategies that control genome-wide patterns of transcriptional response to regulatory signals, development and disease remains a key, unresolved issue. Under this Grant, we have investigated the integration of transcriptional programs by coactivators and corepressors, establishing their role in regulated gene transcription by DMA binding transcription factors, and also established the critical role of specific corepressor complex components in cofactor exchange in ligand- dependent gene activation. An unexpected role of a corepressor dependent recruitment of ubiquitylation/19S proteosome machinery in gene activation, and PARP1 as a sensor for linking specific signaling pathway to programs of transcriptional response have been discovered. Investigation of pituitary gland development as a model has permitted the in vivo characterization of these principles, and the demonstration that cell-type specification is achieved by synergistic actions of specific interacting transcription factors induced in overlapping patterns by opposing signaling gradients. In this competitive renewal, we will focus on the use of a newly-developed genome-wide location analysis method to explore the novel aspects of gene regulation and epigenetic control of transcriptional activation programs. We will explore specific epigenetic strategies of gene regulation during development and the molecular mechanisms underlying boundary element function. The hypothesis that specific gene activation programs unexpectedly require the actions of specific histone demethylases will be tested, and the underlying molecular mechanisms will be explored. Based on the discovery of the sensor function of PARP1, we will investigate the hypothesis that the basic strategy by which poly (ADP-ribose) polymerase functions in nuclear receptor-dependent gene activation involves topoisomerase-dependent DNA nicking with activation of PARP1 enzymatic action to dismiss histone H1 from a specific nucleosome. A novel aspect of LEF/TCF independent B-catenin function in cell lineage determination versus proliferation events will be explored using Pit1 gene regulation as a model. These approaches combine genomics, genetic and molecular biological approaches, providing novel insights into aspects of molecular mechanisms of regulated gene expression and organogenesis, and will provide specific insights into the molecular strategies underlying coordinated programs of gene response.
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