Jill L. Johnson, Ph.D.

Summary: Many human diseases, including Alzheimer’s disease and cystic fibrosis, are due to mutations in DNA that result in misfolded proteins.  Sometimes misfolded proteins are simply degraded by the cell.  At other times, misfolded proteins causes aggregates that are harmful to the cell.  The cell contains proteins, called molecular chaperones, that help other proteins fold correctly.  My lab studies one of these chaperones, called heat shock protein 90 kDa, or Hsp90.  Hsp90 is one of the most abundant proteins in the cell, helping 10-15% of all proteins fold correctly.  However, little is known about how it actually recognizes misfolded proteins and mediates their proper folding.  We use yeast as a model organism to understand how Hsp90 and its team of helper proteins, called co-chaperones, work together to promote protein folding.  We are currently focusing on a protein in yeast called Ura2 that requires Hsp90 for function.  Ura2 is required to make UTP, one of the components of DNA, and the human homolog of Ura2 is overexpressed in some cancer cells.  Because cells lacking Ura2 have specific growth defects, cells that contain mutations in Hsp90 or co-chaperones should have similar growth defects.  We are currently establishing the tools we need to better understand how Ura2 interacts with Hsp90 and why Hsp90 is required for Ura2 function.

Minimum Classes: N/A

Projects: Ura2 is a very big protein, over 2000 amino acids, and we want to narrow down which part of Ura2 interacts with Hsp90 and the co-chaperone Cpr6.  INBRE students working in my lab will gain experience in using site directed mutagenesis of either Hsp90 or Ura2 to understand how the two proteins interact.  We will make mutations in either protein then determine if they still interact by measuring the ability of the two proteins to form a complex in yeast cells. Another potential project is to use genetic screens in yeast to make variants of Ura2 that no longer require Hsp90.  This would allow us to better understand why some proteins require Hsp90 to help them fold while closely related proteins do not.