Transcriptional Repressor DREAM Interacts with Thyroid Transcription Factor-1 and Regulates Thyroglobulin Gene Expression

Marcos Rivas,Britt Mellström,José R Naranjo,Pilar Santisteban

doi:10.1074/jbc.m403526200

Marcos Rivas, Britt Mellström + Show 2 more

Open Access

https://doi.org/10.1074/jbc.m403526200

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Abstract

Tissue-specific gene expression depends on the interaction between tissue-specific and general transcription factors. DREAM is a Ca2+-dependent transcriptional repressor widely expressed in the brain where it participates in nociception through its control of prodynorphin gene expression. In the periphery, DREAM is highly expressed in the thyroid gland, the immune system, and the reproductive organs. Here, we show that DREAM interacts with thyroid-specific transcription factor TTF-1 and regulates the expression of the thyroglobulin (Tg) gene. The mechanism also involves binding of DREAM to the thyroglobulin promoter and blockage of TTF-1-mediated transactivation. The TSH/cAMP pathway and Ca2+ signaling regulate DREAM-mediated transcriptional repression of the thyroglobulin gene. Furthermore, chromatin immunoprecipitation experiments in FRTL-5 cells confirmed that Tg is a bona fide target gene for DREAM transrepression in thyroid follicular cells.

Highlights

Tissue-specific gene expression depends on the interaction between tissue-specific and general transcription factors
DREAM Is Expressed in Follicular Thyroid Cells—To investigate the functional role of the high basal levels of DREAM mRNA in the thyroid gland [17] we used rat FRTL-5 thyroid follicular cells, a model that has been extensively used to study thyroid cell differentiation
Our results suggest that in FRTL-5 thyroid follicular cells DREAM regulates Tg gene expression through a mechanism that involves direct binding to the Tg promoter and interaction with the N-terminal region of transcription factor (TTF)-1

Summary

Introduction

Tissue-specific gene expression depends on the interaction between tissue-specific and general transcription factors. We show that DREAM interacts with thyroid-specific transcription factor TTF-1 and regulates the expression of the thyroglobulin (Tg) gene. 1 The abbreviations used are: Tg, thyroglobulin; DRE, downstream regulatory element; CRE, cAMP response element; CREB, CRE-binding protein; EMSA, electrophoretic mobility shift assay; TTF, thyroid transcription factor; PI, phosphatidylinositol; TSH, thyroid-stimulating hormone; wt, wild type; CAT, chloramphenicol acetyltransferase; GST, glutathione S-transferase; RT, reverse transcriptase; ChIP, chromatin immunoprecipitation assay. One possibility is the involvement of additional, yet unknown, factor(s) In this regard, it has remained elusive to understand the late expression of the Tg gene, from E14.5, when TTF-1, TTF-2, and Pax-8 are expressed from the beginning of thyroid development, at embryonic day E8.5 in the mouse [6]. The Ca2ϩ-dependent DREAM/CREB interaction displaces CREB from CRE sites and prevents the recruitment of CBP to phospho-CREB, which results in a reduction of CRE-dependent transcription without DREAM binding to the CRE site [22]

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