Integrative Chemical Biology Study Of The Hnf4a/Taf4/Taf12 Complex And Its Implication In Diabetes
Reference : PhD Christophe ROMIER
Offer publication : April 6, 2016
PROJECT : Introduction
Transcription factor HNF4A has been shown to play an important role in gene expression in the intestinal epithelium, in the liver and in the beta cells of the pancreas. In these latter cells, loss of HNF4A results in a hyperinsulinemia and glucose intolerance.
Mutations of HNF4A have been shown to induce the MODY1 (monogenic diabetes called maturity onset of diabetes in the young) type of diabetes. Patients with MODY1 show defects in insulin secretion upon stimulation by glucose and arginine, and decreased triglycerides and lipids in the serum, suggesting that the functions of HNF4A in the liver and pancreas are affected.
HNF4A is part of the nuclear receptor family and possesses the characteristic of this family with an N-terminal region of unrecognized role, a DNA recognition zinc finger domain (DNA-binding domain, DBD) that is separated from the ligand binding domain (ligand binding domain, LBD) by a hinge
region. Small molecules capable of binding to the HNF4A LBD and to modulate in vivo its activity have been reported.
Crystallographic studies have characterized the dimerization mode of HNF4A, its DNA recognition mode by the DBD, the communication between the DBD and LBD domains, and recognition of the latter domain by co-activator proteins. Mutations causing the MODY1 disease are found in different
parts of HNF4A and their role in disease remain poorly understood. Recently, a direct interaction between HNF4A and the complex formed by the TAF4 and TAF12 subunits of the general transcription factor TFIID has been demonstrated. This interaction appears to be driven by the LBD domain of HNF4A and the histone-like motifs of TAF4 and TAF12.
Objectives and project
The objectives of the research project are to further characterize the interactions between HNF4A and TAF4/TAF12, including the deciphering of the exact domains of these proteins involved in complex formation. These data will be used to understand the influence of the mutations observed in the MODY1 disease on complex formation. Similarly the influence on the formation of this complex of known small molecule agonists and antagonists of
HNF4A will be studied. The detailed characterization of the areas of interaction between the three proteins will also enable structural studies of this complex, to understand in
molecular terms the precise interactions between these macromolecules. These data will be used to design new specific mutations for preventing complex formation between HNF4A and TAF4/TAF12. The structural work will also be extended to the characterization of HNF4A/ TAF4/TAF12 in complex with agonists and antagonists of HNF4A. All these data will be used to study, in partnership with our collaborators in Strasbourg, the effect of mutations and molecules of interest on cellular models and in the small animal, in order to develop therapeutic strategies in vivo.WISHED SKILLS : The project is making use of numerous techniques: cloning, expression, purification and biochemical, structural and functional characterization of macromolecular complexes. The common denominator of these approaches is the use of molecular biology and biochemical techniques. A strong experimental basis in these techniques is required. Knowledge but, most importantly, an interest in structural and functional analyses will be necessary to pursue these integrative biology studies.
- EXPERTISES WHICH WILL BE ACQUIRED DURING THE TRAINING : Expertise gained during the project will include: cloning, expression, purification and structural/functional characterization of macromolecular complexes. For the purification steps, techniques of complex reconstitution by
multi-expression in E. coli will be used. For the structural studies, the crystallographic technique will be mostly used, but other techniques (NMR, SAXS, electron microscopy) may be used if required.
Application Deadline : Dec. 31, 2016