The Human Enhancer Blocker CTC-binding Factor Interacts with the Transcription Factor Kaiso

• Published in: The Journal of biological chemistry 2005-12, Vol.280 (52), p.43017-43023
• Main Authors: Defossez, Pierre-Antoine, Kelly, Kevin F., Filion, Guillaume J.P., Pérez-Torrado, Roberto, Magdinier, Frédérique, Menoni, Hervé, Nordgaard, Curtis L., Daniel, Juliet M., Gilson, Eric
• Format: Article
• Language: English
• Subjects: Antibodies, Monoclonal - chemistry; Base Sequence; Binding Sites; Biochemistry, Molecular Biology; CCCTC-Binding Factor; Chromatin Immunoprecipitation; CpG Islands; DNA Methylation; DNA, Complementary - metabolism; DNA-Binding Proteins - metabolism; DNA-Binding Proteins - physiology; Enhancer Elements, Genetic; Genome; Genome, Human; Globins - chemistry; HeLa Cells; Humans; Immunoblotting; Immunology; Immunoprecipitation; Life Sciences; Molecular Sequence Data; Protein Binding; Protein Structure, Tertiary; Repressor Proteins - metabolism; Repressor Proteins - physiology; Spectrophotometry; Transcription Factors - chemistry; Transcription Factors - metabolism; Transcription, Genetic; Two-Hybrid System Techniques; Ultraviolet Rays; Zinc Fingers
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M510802200

CTC-binding factor (CTCF) is a DNA-binding protein of vertebrates that plays essential roles in regulating genome activity through its capacity to act as an enhancer blocker. We performed a yeast two-hybrid screen to identify protein partners of CTCF that could regulate its activity. Using full-length CTCF as bait we recovered Kaiso, a POZ-zinc finger transcription factor, as a specific binding partner. The interaction occurs through a C-terminal region of CTCF and the POZ domain of Kaiso. CTCF and Kaiso are co-expressed in many tissues, and CTCF was specifically co-immunoprecipitated by several Kaiso monoclonal antibodies from nuclear lysates. Kaiso is a bimodal transcription factor that recognizes methylated CpG dinucleotides or a conserved unmethylated sequence (TNGCAGGA, the Kaiso binding site). We identified one consensus unmethylated Kaiso binding site in close proximity to the CTCF binding site in the human 5′ β-globin insulator. We found, in an insulation assay, that the presence of this Kaiso binding site reduced the enhancer-blocking activity of CTCF. These data suggest that the Kaiso-CTCF interaction negatively regulates CTCF insulator activity.