Thyroid hormone receptor alpha1 directly controls transcription of the beta-catenin gene in intestinal epithelial cells.
Thyroid hormones, T3 and T4, are known regulators of intestine development. The best characterized example is the remodeling of the gastrointestinal tract during amphibian metamorphosis. Thyroid hormones act via nuclear receptors, the TRs, which are T3-dependent transcription factors. We previously showed that intestinal epithelial cell proliferation is controlled by thyroid hormones and the TRalpha gene. To analyze the mechanisms responsible, we studied the expression of genes belonging to and/or activated by the Wnt/beta-catenin pathway, a major actor in the control of physiological and pathological epithelial proliferation in the intestine. We show that T3-TRalpha1 controls the transcription of the beta-catenin gene in an epithelial cell-autonomous way. This is parallel to positive regulation of proliferation-controlling genes such as type D cyclins and c-myc, known targets of the Wnt/beta-catenin. In addition, we show that the regulation of the beta-catenin gene is direct, as TR binds in vitro and in chromatin in vivo to a specific thyroid hormone-responsive element present in intron 1 of this gene. This is the first report concerning in vivo transcriptional control of the beta-catenin gene. As Wnt/beta-catenin plays a crucial role in intestinal tumorigenesis, our observations open a new perspective on the study of TRs as potential tumor inducers.
IFR 128, Laboratoire de Biologie Moléculaire de la Cellule, CNRS UMR 5161, INRA UMR 1237, Ecole Normale Supérieure de Lyon, 46 Allee d'Italie, Lyon 69364, France. Michela.Plateroti@ens-lyon.fr
Michelina
M
Plateroti
Elsa
E
Kress
Jun Ichirou
JI
Mori
Jacques
J
Samarut
D000818:Animals; D000831:Animals, Newborn; D019556:COS Cells; D049109:Cell Proliferation; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D047369:Chromatin Immunoprecipitation; D004247:DNA / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D005786:Gene Expression Regulation; D007421:Intestine, Small / Q000166:cytology*; D007438:Introns; D051379:Mice; D018345:Mice, Knockout; D017422:Sequence Analysis, DNA; D037021:Thyroid Hormone Receptors alpha / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D051176:beta Catenin / Q000235:genetics*
D037021:Thyroid Hormone Receptors alpha; D051176:beta Catenin; D004247:DNA