The amount and type of fat in the diet has been the subject of public health recommendations to prevent obesity, diabetes and atherosclerosis. A considerable body of literature has developed that suggests that eating the majority of calories as fat results in the development of insulin resistance and type II diabetes mellitus. Much less is known about how non-pathological fluctuations in dietary fat intake alter intracellular metabolism and how these signaling actions affect events in the nucleus. In the course of our studies on mechanisms by which fatty acids regulate gene expression, we discovered that the rate of RNA splicing is inhibited in liver and primary hepatocytes by dietary polyunsaturated fat and by arachidonic acid, respectively. Using the glucose-6-phosphate dehydrogenase (G6PD) enzyme, which lacks transcriptional regulation, as a unique model we have generated a prototype for extending these findings to other genes. Because greater than 60% of genes undergo alternative splicing and many are also regulated by changes in splicing efficiency, these findings will have widespread signficance for determining the proteins expressed within cells throughout development and in muliple cell types. The central hypothesis of this application is that genes that under regulated splicing comtain splicing regulatory regions in an exon. These regions contain juxtaposed splicing silencing and enhancing elements. The binding of splicing inhibitory proteins to the silencer exclude the binding of splicing activators proteins to the enhancer. Polyunsaturated fatty acids regulate the activity of the splicing regulatory proteins by posttranslational modification and/or nuclear abundance. The splicing regulatory region of exon 12 of the G6PD gene is our paradigm for these studies. Despite the ubiquitous need for regulated splicing, little is known about the intracellular signals regulating this process. In the course of these studies, we will define intracellular signal transduction pathways by which nutrients and nutritional status can alter the activity or abundance of splicing regulatory proteins. Thus, the experiments in the current proposal will provide new data on regulation of splicing pre se and define a new pathway by which nutrients regulate gene expression.
The amount and type of fat in the diet has been the subject of public health recommendations to prevent obesity, diabetes and atherosclerosis. A considerable body of literature has developed that suggests that eating the majority of calories as fat results in the development of insulin resistance and type II diabetes mellitus. In addition, the amount and type of fat in the diet can regulate the levels of serum cholesterol and triglycerides, risk factors for atherosclerosis. This project will provide important new data on the ways in which dietary fat can regulate intracellular metabolism.
|Cyphert, T J; Suchanek, A L; Griffith, B N et al. (2013) Starvation actively inhibits splicing of glucose-6-phosphate dehydrogenase mRNA via a bifunctional ESE/ESS element bound by hnRNP K. Biochim Biophys Acta 1829:905-15|
|Kohan, Alison B; Qing, Yang; Cyphert, Holly A et al. (2011) Chylomicron remnants and nonesterified fatty acids differ in their ability to inhibit genes involved in lipogenesis in rats. J Nutr 141:171-6|
|Kohan, Alison B; Talukdar, Indrani; Walsh, Callee M et al. (2009) A role for AMPK in the inhibition of glucose-6-phosphate dehydrogenase by polyunsaturated fatty acids. Biochem Biophys Res Commun 388:117-21|
|Griffith, Brian N; Walsh, Callee M; Szeszel-Fedorowicz, Wioletta et al. (2006) Identification of hnRNPs K, L and A2/B1 as candidate proteins involved in the nutritional regulation of mRNA splicing. Biochim Biophys Acta 1759:552-61|