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Molecular and Cellular Biology, December 1998, p. 7590-7601, Vol. 18, No. 12
Section of Genetics and Development, Cornell
University, Ithaca, New York 14853-2703
Received 29 April 1998/Returned for modification 16 June
1998/Accepted 9 September 1998
In the Saccharomyces cerevisiae Msh2p-Msh6p complex,
mutations that were predicted to disrupt ATP binding, ATP hydrolysis, or both activities in each subunit were created. Mutations in either
subunit resulted in a mismatch repair defect, and overexpression of
either mutant subunit in a wild-type strain resulted in a dominant negative phenotype. Msh2p-Msh6p complexes bearing one or both mutant
subunits were analyzed for binding to DNA containing base pair
mismatches. None of the mutant complexes displayed a significant defect
in mismatch binding; however, unlike wild-type protein, all mutant
combinations continued to display mismatch binding specificity in the
presence of ATP and did not display ATP-dependent conformational
changes as measured by limited trypsin protease digestion. Both
wild-type complex and complexes defective in the Msh2p ATPase displayed
ATPase activities that were modulated by mismatch and homoduplex DNA
substrates. Complexes defective in the Msh6p ATPase, however, displayed
weak ATPase activities that were unaffected by the presence of DNA
substrate. The results from these studies suggest that the Msh2p and
Msh6p subunits of the Msh2p-Msh6p complex play important and
coordinated roles in postmismatch recognition steps that involve ATP
hydrolysis. Furthermore, our data support a model whereby Msh6p uses
its ATP binding or hydrolysis activity to coordinate mismatch binding
with additional mismatch repair components.
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Saccharomyces cerevisiae Msh2p and Msh6p
ATPase Activities Are Both Required during Mismatch Repair
*
Corresponding author. Mailing address: Section of
Genetics and Development, Cornell University, 459 Biotechnology
Building, Ithaca, NY 14853-2703. Phone: (607) 254-4811. Fax: (607)
255-6249. E-mail: eea3{at}cornell.edu.
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