The catenin p120ctn inhibits Kaiso-mediated transcriptional repression of the beta-catenin/TCF target gene matrilysin.
The POZ-zinc finger transcription factor Kaiso was first identified as a specific binding partner for the Armadillo catenin and cell adhesion cofactor, p120ctn. Kaiso is a unique POZ protein with bi-modal DNA-binding properties; it associates with a sequence-specific DNA consensus Kaiso binding site (KBS) or methylated CpG dinucleotides, and regulates transcription of artificial promoters containing either site. Interestingly, the promoter of the Wnt/beta-catenin/TCF target gene matrilysin possesses two conserved copies of the KBS, which suggested that Kaiso might regulate matrilysin expression. In this study, we demonstrate using chromatin immunoprecipitation analysis that Kaiso associates with the matrilysin promoter in vivo. Minimal promoter assays further confirmed that Kaiso specifically repressed transcription of the matrilysin promoter; mutation of the KBS element or RNAi-mediated depletion of Kaiso abrogated this effect. More importantly, Kaiso blocked beta-catenin-mediated activation of the matrilysin promoter. Consistent with our previous findings, both Kaiso-DNA binding and Kaiso-mediated transcriptional repression of the matrilysin promoter were inhibited by overexpression of wild-type p120ctn, but not by a p120ctn mutant exhibiting impaired nuclear import. Collectively, our data establish Kaiso as a sequence-specific transcriptional repressor of the matrilysin promoter, and suggest that p120ctn and beta-catenin act in a synergistic manner, via distinct mechanisms, to activate matrilysin expression.
Spring
Christopher M
CM
Department of Biology, LSB-331, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4K1.
Kelly
Kevin F
KF
O'Kelly
Ita
I
Graham
Monica
M
Crawford
Howard C
HC
Daniel
Juliet M
JM
D000818:Animals; D001483:Base Sequence; D051177:Catenins; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000502:physiology*; D047369:Chromatin Immunoprecipitation; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D015536:Down-Regulation; D005786:Gene Expression Regulation; D006801:Humans; D020783:Matrix Metalloproteinase 7 / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D034622:RNA Interference; D012097:Repressor Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000502:physiology; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000502:physiology; D014158:Transcription, Genetic; D051176:beta Catenin; D000095002:Delta Catenin
C495270:CTNNB1 protein, human; C495267:CTNNB1 protein, mouse; D051177:Catenins; D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D010750:Phosphoproteins; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C492254:ZBTB33 protein, human; D051176:beta Catenin; D020783:Matrix Metalloproteinase 7; D000095002:Delta Catenin