Epigenetic regulation of nutrient sensing in the prostate

It is clear that a broad diet, with plenty of fresh fruit and vegetables is required for growth as a child and health as an adult. Surprisingly little is really understood of how many of these food substances help the body to stay healthy. A family of proteins in human cells, called nuclear receptors, bind to small substances, which are part of a healthy diet, such as vitamins. Each receptor acts like a lock, and binds to a specific substance or group of closely related ones, like a key. These receptors are attached to specific genes inside cells, and when the correct key is in the lock it is able to unfold a gene and allow it to be turned on. The gene then makes a protein which controls how the cell grows and dies. This unfolding is known as epigenetics and is very tightly controlled because not every cell needs every gene to function correctly. This is important because it has become clear that even in adults the body still grows. To keep size constant the body controls the rate at which cells grow, divide and die, with those that die being replaced by new ones. This depends on the correct genes being unfolded at the right time and others being kept locked away. Sometimes in old age or during cancer these controls are lost and lead to problems. In men for example this can affect how the size of one gland, the prostate, is controlled. The understanding that food signals can bind to specific receptors and control the function of cells is important and this grant will analyse the direct mechanisms by which these nutrient signals are sensed, often balanced with other signals, and act to unfold specific gene targets. This will help other scientists to understand what is important in a healthy diet and help people of all ages to be more healthy and live longer.

Mechanisms which link dietary-input to genomic regulation are central to promoting healthy aging. The nuclear receptor superfamily binds a range of lipophillic micro and macro nutrients and thereby regulates a range of gene targets associated with proliferation and differentiation. Central to these actions is the association of nuclear receptors with other proteins in large complexes which can locally remodel chromatin around the promoter regions where these complexes bind. The expression and co-localisation of co-repressor components in these complexes are central to determining the ability to remodel chromation and thus regulate target genes. Recently it has become apparent that the overt nutrient sensing capacity of nuclear receptors operates not only in the gut but elsewhere in the body. One such site is the prostate gland which expresses a broad cohort of dietary sensing nuclear receptors. Understanding the co-ordinate expression and responses of this family, combined with its epigenetic and transcriptional actions is central to developing an integrative and predicative model of nutrient sensing of nuclear receptors. Relevance to Diet and Health Theme: The current proposal will establish the dynamic expression profiles to key dietary sensing nuclear receptors and associated co-factors in a range of normal cell line and primary culture models of prostate epithelial cells. Mechanistic approaches will focus on the interaction of one such receptor, the vitamin D receptor, with target gene promoters in response to micro and macro nutrient ligands. The goal is to generate an integrative model that describes how the vitamin D receptor interacts with ligand, co-factors, other dietary and adjacent transcription factors to regulate the specific and spatio-temporal regulation of epigenetic modifications on target gene promoters and co-ordinate gene transcription. This is essential to generating a mechanistic understanding of gene-nutrient interactions. Outline of research objectives: This project unites three international centre of excellence in a novel to configuration to; i. Define mRNA expression using high throughput Q-RT-PCR screening and cellular response signatures of key receptors in non-malignant cell line and primary prostate models. ii. Establish the vitamin D receptor as a model of micro and macro nutrient sensing, to reveal the critical interactions of receptor with co-repressor complexes, sodium butyrate and adjacent transcription factors (eg. p53) on target gene promoters. Interventionist siRNA and transfection approaches will generate a model of transcriptional responses in non-malignant cell line and primary prostate models. iii. Reveal to what extent epigenetic modifications around the binding sites for the vitamin D receptor on target gene promoters (eg. p21 (waf1 cip1)) correlate with the transcriptional responses. This will contribute to the understanding of the histone code and establish in what way it predicts and accounts for promoter responsiveness. Central to this section will be chromatin immunoprecipitation approaches, in both non-malignant cell line and primary prostate models.