Mechanisms of IGF-I gene transcriptional activation by growth hormone signaling

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DESCRIPTION (provided by applicant): Project Summary: This application represents a committed effort of a young physician-scientist to continue his scientific development towards a goal of becoming an independent investigator. With a clinical background in pediatric endocrinology, the broad objectives of his career in health-related research are centered on understanding the integration of hormones on intracellular signaling pathways and gene regulation. The 5-year path described here includes a combination of research training under the mentorship of Dr. Peter Rotwein and coursework to enhance his scientific background. These activities will be conducted at Oregon Health & Science University. The focus of the research proposal is on characterization of the mechanisms by which the transcription factor Stat5b mediates IGF-l gene expression upon growth hormone stimulation, a topic of significant clinical relevance given the critical role of IGF-I in governing many fundamental physiologic processes, including postnatal growth. Specifically, the aims include characterization of sites of the IGF-I gene to which Stat5b binds and proteins that interact with Stat5b to facilitate initiation of transcription. Chromatin immunoprecipitation assays in the context of a physiologic model of acute growth hormone administration to hypophysectomized rats will assess the temporal and spatial kinetics of binding of transcription factors and transcriptional co-activators at enhancers and the two IGF-I promoters, while capturing chromosome conformation (3C) assays will serve to directly link molecular events at two loci. Functional assessments will include assays for reporter gene activity, restriction enzyme accessibility, histone modifications, and gene transcription. Taken together, these studies will provide a comprehensive model of molecular events at the IGF-gene locus upon growth hormone stimulation. Project relevance: Insulin-like growth factor-l is a critical protein in human health and disease states, with roles extending from fundamental processes of childhood growth to contributing to cancer progression. This project seeks to identify the processes by which insulin-like growth factor-l production is controlled by growth hormone.