PubMed Health⌕ Search

Biomedical subjects

D Civitareale

Publications and source records attributed to D Civitareale.

11 recordsLinked to original sources
PubMed1995

Synergistic transcriptional activation of the thyrotropin receptor promoter by cyclic AMP-responsive-element-binding protein and thyroid transcription factor 1.

In this study we have investigated the molecular mechanisms involved in hormonal induction of thyroid-specific transcription of the thyrotropin receptor (TSHr). A cyclic AMP-responsive element (CRE) has been characterized in the minimal TSHr promoter, and promoter activity shown to be also induced by thyroid transcription factor 1 (TTF-1). We here describe a cooperative effect between TTF-1 and CRE-binding protein on the TSHr promoter. Moreover we have identified a second TTF-1-binding site in the minimal promoter, which does not activate TSHr promoter activity but is required for the co-operative activation of the promoter. This report describes a new aspect of thyroid-specific gene expression, namely, how a generic extracellular signal can be interpreted in a thyroid-specific way.

Animals↗
PubMed1995

Cloning and sequence analysis of human thyroid transcription factor 1.

The thyroid transcription factor 1 (TTF-1) is a homeodomain-containing transcription factor that activates the transcriptional activity of thyroid-specific gene promoters by binding to them. Hence, TTF-1 is crucial in the maintenance of the thyroid differentiation phenotype. The authors isolated and analysed the human TTF-1 gene, which shows a striking homology with the rat TTF-1 gene.

Base Sequence↗
PubMed1994

Purification and characterization of thyroid transcription factor 2.

Thyroid transcription factor 2 binds to the promoters of both thyroglobulin and thyroperoxidase genes, two markers of thyroid tissue differentiation, and its binding modulates the activity of both promoters. In this paper we describe the purification of thyroid transcription factor 2 essentially to homogeneity and demonstrate that it is a thyroid-specific DNA-binding protein. Furthermore, we provide a biochemical characterization suggesting that thyroid transcription factor 2 binds to DNA as a dimer and that it is a zinc-finger DNA-binding protein regulated in vitro by the redox state.

Animals↗
PubMed1994

The thyroid hormone inhibits the thyrotropin receptor promoter activity: evidence for a short loop regulation.

Thyrotropin, by binding its specific receptor on the plasma membrane of the thyrocyte, regulates thyroid function and differentiation. In FRTL5 cells, thyrotropin down-regulates the thyrotropin receptor (TSHr) promoter activity and induces the transcription of the alpha form of thyroid hormone receptor (TR-alpha 1). In this study we show that the thyrotropin receptor down-regulation, induced by thyrotropin, is mediated by TR-alpha 1. The thyroid hormone receptor binds, in vitro, the thyrotropin receptor minimal promoter and inhibits promoter activity in cotransfections experiments in CV 1 cells. The inhibition is achieved only in the presence of the thyroid hormone. The TSHr promoter mutated in the thyroid hormone receptor binding site does not bind TR, in vitro, and its activity is not inhibited, in cotransfection experiments, in CV 1 cells. The same mutation abolishes the TSH mediated down-regulation of the TSHr promoter activity in FRTL5 thyroid cells. These results support the hypothesis of a regulatory short loop of thyroid hormone in thyroid cells.

Base Sequence↗
PubMed1994

Sequence-specific DNA recognition by the thyroid transcription factor-1 homeodomain.

The molecular basis for the DNA binding specificity of the thyroid transcription factor 1 homeodomain (TTF-1HD) has been investigated. Methylation and ethylation interference experiments show that the TTF-1HD alone recapitulates the DNA binding properties of the entire protein. Studies carried out with mutant derivatives of TTF-1HD indicate a precise correspondence of some of its amino acid residues with specific bases in its binding site, allowing a crude orientation of the TTF-1HD within the protein-DNA complex. TTF-1HD shows an overall geometry of interaction with DNA similar to that previously observed for Antennapedia class HDs, even though the binding specificities of these two types of HDs are distinct. We demonstrate that the crucial difference between the binding sites of Antennapedia class and TTF-1 HDs is in the motifs 5'-TAAT-3', recognized by Antennapedia, and 5'-CAAG-3', preferentially bound by TTF-1. Furthermore, the binding of wild type and mutants TTF-1 HD to oligonucleotides containing either 5'-TAAT-3' or 5'-CAAG-3' indicate that only in the presence of the latter motif the Gln50 in TTF-1 HD is utilized for DNA recognition. Since the Gln at position 50 is an essential determinant for DNA binding specificity for several other HDs that bind to 5'-TAAT-3' containing sequences, we suggest that utilization by different HDs of key residues may depend on the sequence context and probably follows a precise hierarchy of contacts.

Antennapedia Homeodomain Protein↗
PubMed1993

Thyroid transcription factor 1 activates the promoter of the thyrotropin receptor gene.

The TSH receptor (TSHr) is one of the most important thyroid differentiation markers. The binding of the TSH hormone to its receptor is an essential step in the modulation of thyroid function and differentiation. Here we report that the thyroid transcription factor 1 (TTF1), a transcription factor essential for thyroid-specific gene expression, binds to the TSHr minimal promoter. The promoter, when mutated at this binding site, shows a decreased activity in thyroid cells. In cotransfection experiments in nonthyroid cells, TTF1 is able to trans-activate the TSHr minimal promoter. This finding strengthens the importance of TTF1 in the maintenance of thyroid differentiation. The promoters of the main thyroid differentiation markers thyroglobulin, thyroperoxidase, and now TSHr, are regulated by TTF1.

Animals↗
PubMed1990

The tissue-specific expression of the thyroglobulin gene requires interaction between thyroid-specific and ubiquitous factors.

Thyroid-specific expression of the rat thyroglobulin gene is mediated by transcriptional control. Sufficient DNA sequence information to confer thyroid-specific expression to a heterologous gene is contained between positions -168 and +39. DNA-binding studies have demonstrated that this region interacts with two thyroid-specific factors (TTF-1 and TTF-2), and a ubiquitous factor (UFA). Here we have characterized three elements within the promoter, A, K, and C, which are important for promoter activity in thyroid cells. We have shown by mutational analysis that the interaction of TTF-1 with the A and C regions. UFA with the A region, and TTF-2 with the K region are required for full promoter activity. The complex interactions in the A region can be replaced by the substitution of the UFA/TTF-1-binding site with a high-affinity TTF-1 binding site. There is a correlation between the presence of TTF-1 and TTF-2 DNA-binding activities and the expression of thyroglobulin, which implies that the mechanism restricting thyroglobulin expression to thyroid cells is mediated through the control of the expression, or the activity, of TTF-1 and TTF-2.

Animals↗
PubMed1989

A thyroid-specific nuclear protein essential for tissue-specific expression of the thyroglobulin promoter.

A rat thyroglobulin promoter fragment, capable of directing thyroid-specific transcription, binds at least three different factors, TTF-1, TTF-2 and UFA, which are all present in nuclear extracts of the differentiated rat thyroid cell line FRTL-5. TTF-1 and TTF-2 are FRTL-5 specific, as demonstrated by their absence in nuclear extracts prepared from cell lines that do not express any thyroid-differentiated function, while UFA is present in all cell lines tested. TTF-1 has been extensively purified. It binds to the rat thyroglobulin promoter at three different sites which share sequence homology. Mutations in two of the three sites decrease both binding of TTF-1 in vitro and promoter function in vivo. This suggests that the tissue-specific expression of the thyroglobulin genes is mediated, at least in part, by the presence of a transcription factor exclusively in thyroid cells.

Animals↗
PubMed1987

Partial purification of a thyroid specific nuclear protein recognizing the thyroglobulin promoter.

We have used a gel retardation assay to follow the purification of a calf thyroid nuclear protein that binds to the -70 region of the rat thyroglobulin promoter. The activity producing the observed band shift is thyroid specific. The same shift is in fact observed with extracts prepared from a differentiated rat thyroid cell line which synthesizes and secretes thyroglobulin, while no similar shift is detected when cell unable to express their endogenous thyroglobulin gene or tissues different from thyroid are used as a source of nuclear extract. Competition experiments suggest that the same protein may bind at two different sites within the promoter. The two sites display considerable sequence homology. Sequence comparisons between the rat, calf and human promoter suggest that more than the sequence is the geometry of the promoter which is conserved.

Animals↗