The DNA glycosylase T:G mismatch-specific thymine DNA glycosylase represses thyroid transcription factor-1-activated transcription.
The transcription factor thyroid transcription factor-1 (TTF-1) is a homeodomain-containing protein that belongs to the NK2 family of genes involved in organogenesis. TTF-1 is required for normal development of the forebrain, lung, and thyroid. In a search for factors that regulate TTF-1 transcriptional activity, we isolated three genes (T:G mismatch-specific thymine DNA glycosylase (TDG), homeodomain-interacting protein kinase 2 (HIPK2), and Ajuba), whose products can interact with TTF-1 in yeast and in mammalian cells. TDG is an enzyme involved in base excision repair. In the present paper, we show that TDG acts as a strong repressor of TTF-1 transcriptional activity in a dose-dependent manner, while HIPK2 and Ajuba display no effect on TTF-1 activity, at least under the tested conditions. TDG-mediated inhibition occurs specifically on TTF-1-responsive promoters in thyroid and non thyroid cells. TDG associates with TTF-1 in mammalian cells through the TTF-1 carboxyl-terminal activation domain and is independent of the homeodomain. These findings reveal a previously unsuspected role for the repair enzyme TDG as a transcriptional repressor and open new routes toward the understanding of the regulation of TTF-1 transcriptional activity.
Missero
C
C
Stazione Zoologica A. Dohrn, Villa Comunale, 80121 Napoli, Italy. missero@tigem.it
Pirro
M T
MT
Simeone
S
S
Pischetola
M
M
Di Lauro
R
R
D000818:Animals; D019556:COS Cells; D002460:Cell Line; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005656:Fungal Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009699:N-Glycosyl Hydrolases / Q000737:chemistry*; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D051381:Rats; D044502:Thymine DNA Glycosylase; D013961:Thyroid Gland / Q000378:metabolism; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D020798:Two-Hybrid System Techniques
D018076:DNA, Complementary; D005656:Fungal Proteins; C000614412:NKX2-1 protein, human; C000614416:Nkx2-1 protein, rat; D009687:Nuclear Proteins; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors; C581922:HIPK2 protein, rat; D017346:Protein Serine-Threonine Kinases; D009699:N-Glycosyl Hydrolases; D044502:Thymine DNA Glycosylase; C113921:mismatch-specific thymine uracil-DNA glycosylase