Defining the roles of beta-catenin and plakoglobin in LEF/T-cell factor-dependent transcription using beta-catenin/plakoglobin-null F9 cells.
beta-Catenin functions as a transcriptional regulator in Wnt signaling. Its function is regulated by a specific destruction system. Plakoglobin is a close homologue of beta-catenin in mammalian cells and is regulated in a similar fashion. When beta-catenin or plakoglobin is exogenously expressed in cells, endogenous beta-catenin is stabilized, which complicates estimation of the transcriptional activities of exogenously expressed proteins. To facilitate the design of experiments aimed at investigating the transcriptional activities of beta-catenin and plakoglobin, we utilized F9 cells in which we knocked out endogenous beta-catenin and/or plakoglobin by gene deletion and exogenously expressed wild-type and mutant beta-catenin and/or plakoglobin. We show that C-terminally deleted beta-catenin, but not plakoglobin, has a strong dominant-negative effect on transcription without altering the nuclear accumulation of beta-catenin. Moreover, we show that Wnt-3a activation of LEF/T-cell factor (TCF)-dependent transcription depends on beta-catenin but not on plakoglobin. Using chimeras of beta-catenin and plakoglobin, we demonstrate that plakoglobin has the potential to function in transcriptional regulation but is not responsible for Wnt-3a signaling in F9 cells. Our data show that preferential nuclear accumulation of beta-catenin is not necessarily linked to its transcriptional activity. We also clearly demonstrate that plakoglobin is insufficient for LEF/TCF-dependent transcriptional activation by Wnt-3a in F9 cells.
Shimizu
Masayuki
M
Division of Cellular Interactions, Institute of Molecular Embryology and Genetics, Kumamoto University, Honjo 2-2-1, Kumamoto 860-0811, Japan.
Fukunaga
Yoshitaka
Y
Ikenouchi
Junichi
J
Nagafuchi
Akira
A
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005786:Gene Expression Regulation; D051379:Mice; D009154:Mutation / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D051820:TCF Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics*; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism; D060508:Wnt3 Protein; D060509:Wnt3A Protein; D051176:beta Catenin / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism*; D051185:gamma Catenin / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism*
D011994:Recombinant Proteins; D051820:TCF Transcription Factors; D051153:Wnt Proteins; D060508:Wnt3 Protein; D060509:Wnt3A Protein; C555511:Wnt3a protein, mouse; D051176:beta Catenin; D051185:gamma Catenin