National Center for
2LT7: Solution NMR structure of Kaiso zinc finger DNA binding domain in complex with Kaiso binding site DNA
Molecular basis for recognition of methylated and specific DNA sequences by the zinc finger protein Kaiso
Proc. Natl. Acad. Sci. U. S. A. (2012) 109 p.15229-15234
Methylation of CpG dinucleotides in DNA is a common epigenetic modification in eukaryotes that plays a central role in maintenance of genome stability, gene silencing, genomic imprinting, development, and disease. Kaiso, a bifunctional Cys(2)His(2) zinc finger protein implicated in tumor-cell proliferation, binds to both methylated CpG (mCpG) sites and a specific nonmethylated DNA motif (TCCTGCNA) and represses transcription by recruiting chromatin remodeling corepression machinery to target genes. Here we report structures of the Kaiso zinc finger DNA-binding domain in complex with its nonmethylated, sequence-specific DNA target (KBS) and with a symmetrically methylated DNA sequence derived from the promoter region of E-cadherin. Recognition of specific bases in the major groove of the core KBS and mCpG sites is accomplished through both classical and methyl CH...O hydrogen-bonding interactions with residues in the first two zinc fingers, whereas residues in the C-terminal extension following the third zinc finger bind in the opposing minor groove and are required for high-affinity binding. The C-terminal region is disordered in the free protein and adopts an ordered structure upon binding to DNA. The structures of these Kaiso complexes provide insights into the mechanism by which a zinc finger protein can recognize mCpG sites as well as a specific, nonmethylated regulatory DNA sequence.