This proposal focuses on the structural and functional characterization of the hepatocyte nuclear factor 4 alpha (HNF4a), a master transcriptional regulator of metabolic gene programs. HNF4a does not respond to ligand binding, but instead appears to rely on methylation and phosphorylation, and on the induction of coactivators for regulating its transcriptional activity. Our recent structural characterization of HNF4a reveals multiple domain-domain interactions that were unanticipated. A highly interconnected domain arrangement links subunit dimerization to both DNA and coactivator binding. We wish to validate this understanding of the receptor's allosteric arrangement using a series of biochemical and cell-based studies that probe these inter-domain connections. We also found several posttranslational modifications that map to key domain-domain junctions. Therefore, a second goal is to understand the allosteric mechanism by which covalent modifications are transmitted to the DNA binding domain of the receptor. The third goal is to expand our structural and mechanistic understanding of how coactivators interact with HNF4a. Here we will test a novel hypothesis that some coactivators, including PGC-1a, can physically drive and stabilize the productive complex of HNF4a on DNA.

Public Health Relevance

The studies we propose are focused on HNF4a, a master regulator of genes in the liver and in pancreatic islet cells. HNF4a regulates the production of glucose and insulin, and has been linked to a form of diabetes. To understand the way in which HNF4a functions, we will apply techniques that allow us visualize its protein architecture, and examine its interactions with other proteins.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK094147-02
Application #
8339923
Study Section
Molecular and Cellular Endocrinology Study Section (MCE)
Program Officer
Margolis, Ronald N
Project Start
2011-09-29
Project End
2015-08-31
Budget Start
2012-09-01
Budget End
2013-08-31
Support Year
2
Fiscal Year
2012
Total Cost
$424,125
Indirect Cost
$206,625
Name
Sanford-Burnham Medical Research Institute
Department
Type
DUNS #
020520466
City
La Jolla
State
CA
Country
United States
Zip Code
92037
Huang, Pengxiang; Chandra, Vikas; Rastinejad, Fraydoon (2014) Retinoic acid actions through mammalian nuclear receptors. Chem Rev 114:233-54
Rastinejad, Fraydoon; Huang, Pengxiang; Chandra, Vikas et al. (2013) Understanding nuclear receptor form and function using structural biology. J Mol Endocrinol 51:T1-T21
Chandra, Vikas; Huang, Pengxiang; Potluri, Nalini et al. (2013) Multidomain integration in the structure of the HNF-4? nuclear receptor complex. Nature 495:394-8