Engineering a high-affinity methyl-CpG-binding protein

Core members of the MBD protein family (MeCP2, MBD1, MBD2 and MBD4) share a methyl-CpG- binding,domain,that,has,a,specific,affinity for methylated,CpG,sites,in,double-stranded,DNA. By multimerizing the MDB domain of Mbd1, we engineered,a poly-MBD protein that displays,methyl- CpG-specific binding,in vitro with,a dissociation constant,that,is .50-fold higher,than,that,of a monomeric,MBD. Poly-MBD proteins,also localize to methylated,foci in cells and,can,deliver a functional domain,to reporter,constructs,in vivo. We propose that poly-MBD proteins,are sensitive,reagents,for the detection,of DNA methylation,levels in isolated native,DNA and,for cytological,detection,of chro- mosomal,CpG methylation.