S100A3 is a novel target gene of Kaiso in mouse skin

Kaiso is a protein that binds methylated DNA and belongs to the BTB/POZ family of transcription fac tors. Kaiso contains two functional domains, includ ing a BTB/POZ domain in the N terminus and a C2H2 type C terminal domain containing three zinc fingers [1]. This bimodal DNA binding protein specifically recognizes both methylated mCpGmCpG and nonmethylated CTGCNA sequences (below, the Kaiso binding site is referred to as KBS) [24]. The nonmethylated CTGCNA sequence is present in pro moter regions of Wnt11, matrilysin 7, and Siamois genes in Xenopus laevis frogs. It was shown that the presence of 5 hydroxymethylcytosine within the KBS inhibits Kaiso DNA binding [5]. However, it should be noted that there is no agreement within the scien tific community regarding which of the DNA binding activities of Kaiso (against methylated regions, nonm ethylated sequences or both) represents its main activ ity in vivo. It has been demonstrated that Kaiso is essential for amphibian development. A reduction in Kaiso levels in Xenopus laevis frogs and Danio rerio fish results in embryonic lethality due to premature gene activation in blastulae and increased expression of the Wnt11 gene [68]. On the other hand, Kaiso null mice show no phenotype. However, when Kaiso/y mice were crossed with APC/Min mice, the progeny acquired resistance to intestinal tumorigenesis. The direct targets of Kaiso have not yet been