Structure and function of Kaiso. (A) Kaiso is a 672 amino acid protein, which includes an N-terminal POZ/BTB domain required for protein-protein interactions, a nuclear localization signal, and three tandem C2H2 zinc finger domains responsible for DNA binding; numbers represent the amino acid borders of each domain. Shown below the zinc finger domains are the two motifs to which Kaiso has been shown to bind in vitro. (B) The current model for Kaiso’s activity at promoters: in the left figure, Kaiso’s 3 C2H2 zinc finger domains recognize and bind methylated DNA, recruiting the NCoR histone deacetylation complex to the region and causing the loss of active chromatin marks and the repression of the adjacent promoter. The figure on the right shows an unmethylated promoter, which is not recognized by Kaiso. As a result, the NCoR histone deacetylation complex is not recruited to the region and surrounding histones remain acetylated allowing for expression of the promoter.