Characterization of Arabidopsis thaliana methyl-CpG-binding domain (MBD) proteins
Article first published online: 22 MAY 2003
The Plant Journal
Volume 34, Issue 5, pages 565–572, June 2003
How to Cite
Zemach, A. and Grafi, G. (2003), Characterization of Arabidopsis thaliana methyl-CpG-binding domain (MBD) proteins. The Plant Journal, 34: 565–572. doi: 10.1046/j.1365-313X.2003.01756.x
- Issue published online: 22 MAY 2003
- Article first published online: 22 MAY 2003
- Received 2 January 2003; accepted 13 February 2003.
- DNA methylation;
- Methyl-CpG-Binding Domain (MBD);
- histone deacetylase (HDAC);
- Arabidopsis thaliana
Cytosine methylation at symmetrical CpG and CpNpG sequences plays a key role in the epigenetic control of plant growth and development; yet, the way by which the methylation signal is interpreted into a functional state has not been elucidated. In animals, the methylation signal is recognized by methyl-CpG-binding domain (MBD) proteins that specifically bind methylated CpG dinucleotides. In Arabidopsis thaliana, 12 putative MBD proteins were identified and classified into seven subclasses. Here, we characterized six MBD proteins representing four subclasses (II, III, IV, and VI) of the Arabidopsis MBD family. We found that AtMBD7 (subclass VI), a unique protein containing a double MBD motif, as well as AtMBD5 and AtMBD6 (subclass IV), bind specifically symmetrically methylated CpG sites. The MBD motif derived from AtMBD6, but not from AtMBD2, was sufficient for binding methylated CpG dinucleotides. AtMBD6 precipitated histone deacetylase (HDAC) activity from the leaf nuclear extract. The examined AtMBD proteins neither bound methylated CpNpG sequences nor did they display DNA demethylase activity. Our results suggest that AtMBD5, AtMBD6, and AtMBD7 are likely to function in Arabidopsis plants as mediators of the CpG methylation, linking DNA methylation-induced gene silencing with histone deacetylation.