Published online 28 April 2006
Article |
The molecular mechanism of DNA damage recognition by MutS homologs and its consequences for cell death response
Department of Physics, Wake Forest University NC 27109, USA 1 Department of Cancer Biology, Wake Forest University School of Medicine, Medical Center Boulevard Winston-Salem, NC 27157, USA 2 Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard Winston-Salem, NC 27157, USA
*To whom correspondence should be addressed. Tel: +1 336 713 4077; Fax: +1 336 716 0255; Email: kdrotsch{at}wfubmc.edu
Received November 16, 2006. Revised December 21, 2006. Accepted March 28, 2006.
We determined the molecular mechanism of cell death response by MutS homologs in distinction to the repair event. Key protein–DNA contacts differ in the interaction of MutS homologs with cisplatinated versus mismatched DNA. Mutational analyses of protein–DNA contacts, which were predicted by molecular dynamics (MD) simulations, were performed. Mutations in suggested interaction sites can affect repair and cell death response independently, and to different extents. A glutamate residue is identified as the key contact with cisplatin-DNA. Mutation of the residue increases cisplatin resistance due to increased non-specific DNA binding. In contrast, the conserved phenylalanine that is instrumental and indispensable for mismatch recognition during repair is not required for cisplatin cytotoxicity. These differences in protein–DNA interactions are translated into localized conformational changes that affect nucleotide requirements and inter-subunit interactions. Specifically, the ability for ATP binding/hydrolysis has little consequence for the MMR-dependent damage response. As a consequence, intersubunit contacts are altered that most likely affect the interaction with downstream proteins. We here describe the interaction of MutS homologs with DNA damage, as it differs from the interaction with a mismatch, and its structural translation into all other functional regions of the protein as a mechanism to initiate cell death response and concomitantly inhibit repair.