Mismatch repair in methylated DNA. Structure and activity of the mismatch-specific thymine glycosylase domain of methyl-CpG-binding protein MBD4

• Type of Material: Article
• Authors: Peiying Wu, Emory University; Chen Qiu, Emory University; Anjum Sohail, Wayne State University; Xing Zhang, Emory University; Ashok S. Bhagwat, Wayne State University; Xiaodong Cheng, Emory University
• Language: English
• Date: 2003-02-14
• Publisher: American Society for Biochemistry and Molecular Biology
• Publication Version: Final Published Version
• Copyright Statement: © 2003 by The American Society for Biochemistry and Molecular Biology, Inc.
• Final Published Version (URL): http://www.jbc.org/content/278/7/5285.long
• Title of Journal or Parent Work: Journal of Biological Chemistry
• ISSN: 0021-9258
• Volume: 278
• Issue: 7
• Start Page: 5285
• End Page: 5291
• Grant/Funding Information: This work was supported in part by National Institutes of Health Grants GM49245 (to X. C.) and GM57200 (to A. S. B) and the Georgia Research Alliance.
• Research Categories: Chemistry, Biochemistry; Chemistry, General

Abstract

MBD4 is a member of the methyl-CpG-binding protein family. It contains two DNA binding domains, an amino-proximal methyl-CpG binding domain (MBD) and a C-terminal mismatch-specific glycosylase domain. Limited in vitro proteolysis of mouse MBD4 yields two stable fragments: a 139-residue fragment including the MBD, and the other 155-residue fragment including the glycosylase domain. Here we show that the latter fragment is active as a glycosylase on a DNA duplex containing a G:T mismatch within a CpG sequence context. The crystal structure confirmed the C-terminal domain is a member of the helix-hairpin-helix DNA glycosylase superfamily. The MBD4 active site is situated in a cleft that likely orients and binds DNA. Modeling studies suggest the mismatched target nucleotide will be flipped out into the active site where candidate residues for catalysis and substrate specificity are present.