The transcriptional repressor DREAM is involved in thyroid gene expression.
Downstream regulatory element antagonistic modulator (DREAM) was originally identified in neuroendocrine cells as a calcium-binding protein that specifically binds to downstream regulatory elements (DRE) on DNA, and represses transcription of its target genes. To explore the possibility that DREAM may regulate the endocrine activity of the thyroid gland, we analyzed its mRNA expression in undifferentiated and differentiated thyroid cells. We demonstrated that DREAM is expressed in the normal thyroid tissue as well as in differentiated thyroid cells in culture while it is absent in FRT poorly differentiated cells. In the present work, we also show that DREAM specifically binds to DRE sites identified in the 5' untranslated region (UTR) of the thyroid-specific transcription factors Pax8 and TTF-2/FoxE1 in a calcium-dependent manner. By gel retardation assays we demonstrated that thapsigargin treatment increases the binding of DREAM to the DRE sequences present in Pax8 and TTF-2/Foxe1 5' UTRs, and this correlates with a significant reduction of the expression of these genes. Interestingly, in poorly differentiated thyroid cells overexpression of exogenous DREAM strongly inhibits Pax8 expression. Moreover, we provide evidence that a mutated form of DREAM unable to bind Ca(2+) interferes with thyroid cell proliferation. Therefore, we propose that in thyroid cells DREAM is a mediator of the calcium-signaling pathway and it is involved in the regulation of thyroid cell function.
D'Andrea
Barbara
B
Istituto di Endocrinologia ed Oncologia Sperimentale-CNR and Dpt. di Biologia e Patologia Cellulare e Molecolare, Via Pansini 5, 80131 Napoli, Italy.
Di Palma
Tina
T
Mascia
Anna
A
Motti
Maria Letizia
ML
Viglietto
Giuseppe
G
Nitsch
Lucio
L
Zannini
Mariastella
M
D020121:5' Untranslated Regions / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000502:physiology*; D002454:Cell Differentiation; D002460:Cell Line; D017931:DNA Primers; D004847:Epithelial Cells; D051605:Kv Channel-Interacting Proteins; D016296:Mutagenesis; D051381:Rats; D012016:Reference Values; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016385:TATA Box; D013961:Thyroid Gland / Q000166:cytology / Q000502:physiology*; D014158:Transcription, Genetic
D020121:5' Untranslated Regions; D002135:Calcium-Binding Proteins; D017931:DNA Primers; C496760:Kcnip3 protein, rat; D051605:Kv Channel-Interacting Proteins; D012097:Repressor Proteins; D002118:Calcium