Multi-complex Formation by HNF1a: Beta-Cell Master Regulator

Our long-term goal Is to understand the molecular mechanisms of gene regulation by the transcription factors governing b-cell development and function, and the molecular basis of diabetes-causing mutations found in them. We have chosen HNFla as a model system which has been identified as a culprit gene product for MODY3.HNFla ISa master switch in b-cell differentiation, growth and function, and its mutations accounts for the majority of MODYcases. Numerous point mutations are found in HNFla and they could be instructive as to the mechanism of transcription regulation and how the mutations disrupt the normal function at the molecular level. As a gene-specific transcription factor, HNFla initiates transcription by specifically recognizing the promoter region of target genes and mediating interactions with a host of coregulators. However, detailed structural information on the assembly of higher-order transcription complexes is not well known. Therefore, we propose to (1) solve the crystal structure of HNFla in complex with its target DNAand DeaH, (2) solve the crystal structure of HNFla in complex with its target DNAand p300, (3) identify additional b-cell specific transcriptional coregulators for structural studies, and (4) examine the biological, biochemical and biophysical effects of diabetes-causing mutations. These findings should aid overall understanding of transcrIption control Involved In b-cell deveopment and function, and rational targeting of HNFla in order to modulate Its activities for promoting maturation, prolonging survival and boosting Insulin secretion, and to reverse the adverse effects by the mutations, thus potential treatment for diabetes. General Audience Summaryl People with either a low level of fully-developed or defective mature b-cells would need b-cell replacement or b-cell function boost to maintain glucose homeostasis. There is a network of transcription factors controlling proper development and normal function of b-cells through their ability to turn on or off specific genes during the critical times. When these transcription factors are defective, Improper development and function of b-cell occur as in the case of genetic mutations In HNFla which cause a inherited dominant form of diabetes known as MODY. Therefore, a better understanding of islet factors that control development could provide new and better ways to promote maturation, prolong survival and boost Insulin secretion in improperlydeveloped, transplanted and/or engineered islet cells. We have been studying (thanks to the JDRFI postdoc fellowship) how HNFla functions and how diabetes mutations disrupt Its functions at the molecular level using a method called x-ray crystallography. This technique allows us to visualize the action of this master switch in three dimensions at high resolution. Since HNFla interacts with DNAand a host of proteins to form a transcription initiation complex and carries out its functions, we propose to determine some of the structures of these higher-order complexes. These structures should enhance our understanding of transcription control involved in b-cell deveopment and function, and rational drug targeting of HNFla in order to modulate its activities for enhancement of b-ce" growth and preservation of b-cell function, and to reverse the adverse effects by the mutations, thus potential treatment for diabetes.