Abstract
Thyroid transcription factor gene 1 (TTF-1) is a homeobox-containing gene involved in thyroid organogenesis. During early thyroid development, the homeobox gene Nkx-2.5 is expressed in thyroid precursor cells coincident with the appearance of TTF-1. The aim of this study was to investigate the molecular mechanisms underlying thyroid-specific gene expression. We show that the Nkx-2.5 C terminus interacts with the TTF-1 homeodomain and, moreover, that the expression of a dominant-negative Nkx-2.5 isoform (N188K) in thyroid cells reduces TTF-1-driven transcription by titrating TTF-1 away from its target DNA. This process reduced the expression of several thyroid-specific genes, including pendrin and thyroglobulin. Similarly, down-regulation of TTF-1 by RNA interference reduced the expression of both genes, whose promoters are sensitive to and directly associate with TTF-1 in the chromatin context. In conclusion, we demonstrate that pendrin and thyroglobulin are downstream targets in vivo of TTF-1, whose action is a prime factor in controlling thyroid differentiation in vivo.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Base Sequence
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Binding Sites
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Blotting, Northern
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Blotting, Western
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Cell Differentiation
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Chloride-Bicarbonate Antiporters / metabolism
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Chloride-Bicarbonate Antiporters / physiology*
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Chromatin
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Chromatin Immunoprecipitation
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DNA / chemistry
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Down-Regulation
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Gene Expression Regulation*
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Genes, Dominant
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HeLa Cells
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Humans
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Immunoprecipitation
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Introns
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Ions
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Membrane Transport Proteins / metabolism
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Membrane Transport Proteins / physiology*
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Molecular Sequence Data
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Nuclear Proteins / chemistry
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Nuclear Proteins / physiology*
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Oligonucleotides / chemistry
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Plasmids / metabolism
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Protein Binding
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Protein Isoforms
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Protein Structure, Tertiary
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RNA Interference
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RNA, Messenger / metabolism
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Rats
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Reverse Transcriptase Polymerase Chain Reaction
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Sulfate Transporters
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Thyroid Gland / metabolism
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Thyroid Neoplasms / metabolism*
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Thyroid Nuclear Factor 1
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Transcription Factors / chemistry
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Transcription Factors / physiology*
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Transfection
Substances
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Chloride-Bicarbonate Antiporters
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Chromatin
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Ions
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Membrane Transport Proteins
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NKX2-1 protein, human
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Nkx2-1 protein, rat
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Nuclear Proteins
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Oligonucleotides
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Protein Isoforms
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RNA, Messenger
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SLC26A4 protein, human
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Slc26A4 protein, rat
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Sulfate Transporters
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Thyroid Nuclear Factor 1
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Transcription Factors
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DNA