The p120ctn-binding partner Kaiso is a bi-modal DNA-binding protein that recognizes both a sequence-specific consensus and methylated CpG dinucleotides

Abstract

The p120(ctn)-binding partner Kaiso is a new member of the POZ-zinc finger family of transcription factors implicated in development and cancer. To understand the role of Kaiso in gene regulation and p120(ctn)-mediated signaling and adhesion, we sought to identify Kaiso-specific DNA binding sequences and potential target genes. Here we demonstrate that Kaiso is a dual specificity DNA-binding protein that recognizes the specific consensus sequence TCCTGCNA as well as methyl-CpG dinucleotides. A minimal core sequence CTGCNA was identified as sufficient for Kaiso binding. Two copies of the Kaiso-binding site are present in the human and murine matrilysin promoters, implicating matrilysin as a candidate target gene for Kaiso. In electrophoretic mobility shift assays, matrilysin promoter-derived oligonucleotide probes formed a complex with GST-Kaiso fusion proteins possessing the zinc finger domain but not with fusion proteins lacking the zinc fingers. We further determined that only Kaiso zinc fingers 2 and 3 were necessary and sufficient for sequence-specific DNA binding. Interestingly, Kaiso also possesses a methyl-CpG-dependent DNA-binding activity distinct from its sequence-specific DNA binding. However, Kaiso has a higher affinity for the TCCTGCNA consensus than for the methyl-CpG sites. Furthermore, the DNA-binding ability of Kaiso with either recognition site was inhibited by p120(ctn). Kaiso thus appears to have two modes of DNA binding and transcriptional repression, both of which may be modulated by its interaction with the adhesion cofactor p120(ctn).

NLS-dependent nuclear localization of p120ctnis necessary to relieve Kaiso-mediated transcriptional repression

“…Kaiso is a nuclear phosphoprotein belonging to the family of POZ-zinc finger transcription factors implicated in tumorigenesis and embryonic development (Albagli et al, 1995;Bardwell and Treisman, 1994). The relevance of the p120 ctn -Kaiso interaction was recently revealed when we discovered that p120 ctn inhibits Kaiso DNA-binding (Daniel et al, 2002) and Kaiso-mediated transcriptional repression of target genes (our unpublished data). Although the inhibition of Kaiso-mediated transcriptional repression by p120 ctn was most likely due to steric hindrance of Kaiso DNA-binding, it remained possible that p120 ctn exerted its inhibitory effect by sequestering Kaiso in the cytosol.…”

“…Our identification of the novel BTB/POZ transcriptional repressor Kaiso as a p120 ctnspecific binding partner (Daniel and Reynolds, 1999) thus raised the exciting possibility that p120 ctn , like β-catenin, regulates gene expression. Indeed, we have found that p120 ctn inhibits both the DNA-binding ability of Kaiso in vitro (Daniel et al, 2002), and Kaiso-mediated transcriptional repression of target genes via the sequence-specific Kaiso consensus site (our unpublished data).…”

p120 and Kaiso RegulateHelicobacter pylori-induced Expression of Matrix Metalloproteinase-7

“…Nuclear p120 relieves transcriptional repression exerted by Kaiso, which acts as a dual specificity repressor that recognizes both sequence-specific consensus sites (CT-GCNA) and methylated CpG nucleotides (Prokhortchouk et al, 2001;Daniel et al, 2002;Park et al, 2005). Because H. pylori infection has been associated with gastric cancer and nuclear mislocalization of p120 in human gastric epithelium (Krueger et al, 2007), we investigated mislocalization of p120 in conjunction with altered expression of the oncogenic molecule MMP-7.…”

“…Interactions between p120 and Kaiso can coordinately regulate genes implicated in carcinogenesis (Daniel and Reynolds, 1999;Daniel et al, 2002;Kelly et al, 2004;Kim et al, 2004;Park et al, 2005;Spring et al, 2005), and translocation of p120 to the nucleus relieves Kaiso-mediated transcriptional repression of mmp-7 (Kelly et al, 2004;Park et al, 2005;Spring et al, 2005). To determine whether H. pylori infection alters total p120 levels, MKN28 cells were cocultured with H. pylori strain 7.13 (MOI ϭ 100) or medium alone and subjected to Western blot analysis ( Figure 3A).…”

Les protéines se liant à l’ADN méthylé : interprètes du code épigénétique

“…Les études structurales de Kaiso et de ses homologues promettent ainsi de définir les propriétés d'un nouveau domaine de liaison à l'ADN méthylé. De façon inattendue, une étude récente montre que Kaiso peut aussi reconnaître une séquence spécifique non méthylée, de sept nucléotides, par l'intermédiaire du même domaine à doigts de zinc [7]. Puisque le domaine à doigts de zinc de Kaiso reconnaît une séquence d'ADN ainsi que les CpG méthylés il n'y a pas incompatibilité entre ces deux spécifici-tés.…”