REGULATION OF ESTROGEN RESPONSIVE GENES

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The long range goal of our research is to understand the mechanisms by which estrogen directs the transcription of genes. This proposal is designed to examine the molecular basis for the biological effects of estrogen during avian reproduction. The egg yolk protein genes are all responsive to estrogen; however, individual differences, in particular the kinetics of induction, are superimposed on this coordinate response to estrogen. Following the administration of estrogen to young birds, very low density apolipoprotein II (apo-II) mRNA appears within 4 hours, vitellogenin (VTG) II and III mRNA appear within 6 hours and a lag of 20 hours is observed before VTG-I mRNA can be measured. The molecular basis of the lag and the reasons for the observed differences is not understood. Our hypothesis is that the specific protein-DNA interactions which occur in chicken liver in response to estrogen perturb the chromatin structure thus marking each individual gene in a unique way. These changes in chromatin determine both the access of transcription factors to the gene and the time course with which the individual gene is activated. The proposed experiments are designed to identify and establish the function of the regulatory elements, to define the time course of changes in chromatin structure across these regions following the administration of estrogen, and to relate these structural changes to the altered rates of transcription that accompany the activation of gene expression. The specific alms of this proposal are to 1) identify the regulatory elements within the first intron of the apo-II gene, 2) identify the regulatory elements in the promoter of the VTG-I gene, and 3) determine the time course of the chromatin alterations that occur across the regulatory elements of the four yolk protein genes in response to estrogen. These studies will rely predominantly on DNA footprinting, site directed mutagenesis, transient transfection, and run-on transcription assays. Estrogen is crucial in reproduction and development as well as in health and disease. Understanding the mechanisms by which estrogen regulates gene expression will provide a basis for understanding abnormal disease states and assisting in therapeutic design.