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PubMed2001

Transcriptional activation of the thyroglobulin promoter directing suicide gene expression by thyroid transcription factor-1 in thyroid cancer cells.

Gene therapy with thyroglobulin (TG) promoter and a prodrug/suicide gene combination may prove useful as a treatment for thyroid carcinoma. However, most poorly differentiated and anaplastic thyroid carcinomas have lost the ability to express the TG gene expression accompanied by loss of transcription factors [thyroid transcription factor-1 (TTF-1), TTF-2, or Pax-8] interacting with the TG promoter. In anticipation of developing transcriptionally targeted gene therapy of TG-nonproducing thyroid carcinomas, we investigated the effect of TTF-1 gene transfer on TG promoter activity and the cytotoxic effect obtained by the TG promoter-driven HSV-TK gene along with ganciclovir in thyroid carcinoma and nonthyroidal cells. Using a chimeric construct containing the 5'-flanking region of the rat TG gene between -826 and +39 bp and the luciferase gene, TG promoter activity was detected in a normal rat thyroid cell line (FRTL-5), but not in a dedifferentiated line of thyroid cells (FRT) expressing Pax-8 but not TTF-1, TTF-2, or TG [TTF-1(-)/TTF-2(-)/Pax-8(+)/TG(-)], or in a human papillary thyroid carcinoma cell line [BHP15-3; TTF-1(-)/TTF-2(-)/Pax-8(-)/TG(-)], a human pulmonary cell line [H441; TTF-1(+)/TTF-2(-)/Pax-8(-)/TG(-)], or a dog kidney epithelial cell line [MDCK; TTF-1(-)/TTF-2(-)/Pax-8(+)/TG(-)]. Cotransfection of the TTF-1 expression vector stimulated TG promoter activity in FRT and BHP15-3 dedifferentiated thyroid cells, but not in H441 pulmonary cells. Only weak activation was observed in MDCK kidney cells. We then constructed recombinant adenovirus vectors, AdTTF-1 and ADTGTK: AdTTF-1 contained cytomegalovirus promoter and rat TTF-1 cDNA; AdTGTK carried the TG promoter-driven HSV-TK gene. Infection with AdTGTK and combined with GCV treatment induced a cytotoxic effect in FRTL-5 cells but not in dedifferentiated thyroid or nonthyroid cells. Cotransduction of AdTTF-1 and AdTGTK permitted 90% cytotoxicity for BHP15-3 and >95% cytotoxicity for FRT, as well as for BHP7-13 and BHP18-21v thyroid cancer cell lines [both/TTF1(-)/TTF-2(-)/Pax-8(+)/TG(-)]. In contrast, little cytotoxicity was seen for H441 and MDCK cell lines even with 300 microg/ml of ganciclovir. These results suggest that cotransduction of a TG promoter-controlled suicide gene and the TTF-1 gene by adenoviral vectors confers transcriptionally targeted gene-mediated cytotoxicity in poorly differentiated thyroid carcinoma cells unable to express the TG gene.

Adenoviridae↗
PubMed1992

Fatty acid regulation of gene expression. Transcriptional and post-transcriptional mechanisms.

Fatty acids are important metabolic substrates and may also be involved in pathological syndromes such as the insulin resistance of diabetes and obesity. We demonstrate here that fatty acids can regulate specific gene expression; mRNAs encoding the fatty acid binding protein adipocyte P2 (aP2) and the Fos-related transcription factor Fra1 are specifically induced at least 20-fold upon treatment of preadipocytes with oleate. For aP2, the effect requires long chain fatty acids and occurs without a generalized activation of the genes linked to adipocyte differentiation. Other fibroblastic cells without preadipocyte characteristics do not induce aP2 mRNA in response to fatty acids. Unlike aP2, Fra1 induction by fatty acids also can be detected in NIH 3T3 and 3T3-C2 fibroblasts. Nuclear transcription assays in 3T3-F442A preadipocytes demonstrate that fatty acids elicit no transcriptional increase in the aP2 gene. Fra1, on the other hand, shows a 3-4-fold increase in transcription. These results demonstrate at least two distinct mechanisms by which fatty acids may influence gene expression.

3T3 Cells↗
PubMed1992

2,3,7,8-Tetrachlorodibenzo-p-dioxin-dependent regulation of transforming growth factors-alpha and -beta 2 expression in a human keratinocyte cell line involves both transcriptional and post-transcriptional control.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a potent modulator of epithelial cell growth and differentiation, has been shown to induce transforming growth factor (TGF)-alpha in cultures of human keratinocytes and in the human keratinocyte cell line, SCC-12F. In this report, we investigated the mechanisms by which TCDD alters TGF-alpha expression. In addition, we studied the actions of TCDD on TGF-beta 1 and TGF-beta 2 expression. Treatment of SCC-12F cells with TCDD resulted in an increase in TGF-alpha and a reduction in TGF-beta 2 mRNA levels while mRNA levels for TGF-beta 1 were unchanged. Changes in TGF-alpha and TGF-beta 2 expression were maximal by 24 h. No change in the rate of transcription of TGF-alpha was detected following treatment with TCDD as determined by nuclear run-off analysis. TCDD treatment resulted in a stabilization of TGF-alpha mRNA as judged by an approximately 2-fold higher level of TGF-alpha mRNA in treated versus control cells in the presence of actinomycin D. In contrast to TGF-alpha, the rate of transcription of TGF-beta 2 was significantly reduced following TCDD treatment. These findings demonstrate that the induction of TGF-alpha expression in SCC-12F cells by TCDD occurs post-transcriptionally, primarily by mRNA stabilization, while TGF-beta 2 expression is reduced due to a decrease in the rate of TGF-beta 2 gene transcription.

Blotting, Northern↗
PubMed1991

Transcriptional and post-transcriptional mechanisms involved in the differential expression of LPS-induced IL-1 and TNF mRNA.

The amplification of cytokine mRNA following incubation of macrophages with inflammatory stimuli and protein synthesis inhibitors has been related to stabilization of labile mRNA species containing the 3'AUUUA consensus sequence. In the present study, cycloheximide-treated lipopolysaccharide (LPS)-stimulated murine peritoneal macrophages had a five- to six-fold increase in tumour necrosis factor (TNF) mRNA when compared to parallel LPS-stimulated controls. Interleukin-1 beta (IL-1 beta) mRNA levels in these cells, however, were significantly lower than the LPS controls. The down-regulation of IL-1 beta by cycloheximide was not apparent for IL-1 alpha mRNA, which had a two- to three-fold increase in the LPS-stimulated cycloheximide-treated macrophages. A similar profile was observed in vivo in which up-regulation of TNF, but not IL-1 beta mRNA, was apparent in mice administered cycloheximide plus LPS relative to LPS alone. Cycloheximide-treated LPS-stimulated macrophages demonstrated a significant increase in transcriptional activity for TNF, but not IL-1 beta, by nuclear run-on transcription assays and an increase in the amount of the nuclear binding factor NFKB when compared to LPS controls. The cycloheximide-mediated increase in TNF mRNA was also related to an increased stability of the TNF message, while no significant increase in stability was apparent in IL-1 beta mRNA. Therefore, the differential expression of TNF and IL-1 beta mRNA in cycloheximide-treated macrophages involves both transcriptional and post-transcriptional regulatory mechanisms.

Animals↗
PubMed1991

Inhibition of DNA binding and transcriptional activity of a nuclear receptor transcription factor by aurothiomalate and other metal ions.

The antirheumatic gold salt aurothiomalate (AuTM) has cellular actions that are consistent with modulation of gene expression. We have tested the hypothesis that an important mode of action of AuTM is inhibition of binding of certain transcription factors to regulatory elements in DNA. The chemistry of transcription factors containing the zinc finger motif makes them candidates for such an interaction with AuTM. In this regard, the interaction of a steroid hormone receptor, the progesterone receptor (PR), with its DNA response element (PRE) was chosen as a suitable model. Nuclear extracts of T-47D human breast cancer cells rich in PR were incubated with radiolabeled PRE, and binding was determined by gel retardation assay. Preincubation of nuclear extract with AuTM caused a concentration-dependent inhibition of binding of PR to PRE (IC50, approximately 3 microM). Other metal ions inhibited binding at higher concentrations, in a rank order correlating with their binding affinity for thiols. Thiomalic acid had no effect in the absence of gold in this system. To test the effect of AuTM on PR-mediated transcription, we transfected the progestin-inducible expression vector pMSG-CAT into T-47D cells. Transfected cells were incubated in the absence or presence of AuTM and treated with the synthetic progestin ORG2058, to induce chloramphenicol acetyl transferase (CAT) activity. With 10 and 100 microM AuTM, there was inhibition to 67 +/- 3% (p = 0.012) and 42 +/- 8% (p = 0.008) of CAT specific activity, respectively, compared with controls. These results demonstrate that AuTM can regulate gene expression and that inhibition of binding of a transcription factor to its response element is a likely mechanism. This provides a molecular model for further study of the antirheumatic action of gold salts.

Cell Nucleus↗
PubMed1990

Hormonal regulation of transcription of rDNA. Purification and characterization of the hormone-regulated transcription factor IC.

Glucocorticoids reversibly inhibit transcription of ribosomal RNA genes in murine lymphosarcoma P1798 cells in culture. Inhibition of rDNA transcription is due to reduction in the amount or activity of an RNA polymerase I transcription factor called transcription factor IC (TFIC). TFIC has been purified over 100,000-fold. The highly purified preparation contains neither RNA polymerase I activity nor any of the conventional RNA polymerase I subunits. TFIC activity co-purifies with three polypeptides of approximately 55, 50, and 42 kDa molecular mass. These polypeptides are present in a stoichiometric ration of 1:1:1.

Animals↗
PubMed1988

Regulation of HLA-DR gene by IFN-gamma. Transcriptional and post-transcriptional control.

IFN-gamma increases the synthesis and level of mRNA of the HLA class I and II genes, in human cells such as melanomas which normally express both classes of molecules. It also induces the surface expression and mRNA synthesis of HLA-DR genes on cells which normally do not express HLA class II genes such as skin fibroblasts. We have investigated the mechanism by which IFN-gamma increases mRNA levels for class II MHC antigens in human cells. For this purpose, we have studied the effect of IFN-gamma on HLA-DR-alpha transcription rate in two different human cell types: VAL melanoma and JDA2 skin fibroblasts. HLA-DR-alpha mRNA is spontaneously produced in VAL cells and its level is enhanced upon IFN-gamma treatment. We demonstrate here that IFN-gamma increases the transcription of HLA-DR-alpha gene in this cell line. However, the discrepancy observed between HLA-DR-alpha mRNA and transcriptional rates led us to postulate that IFN-gamma also regulates the HLA-DR-alpha gene post-transcriptionally. In the course of these experiments, we found also that human skin fibroblasts, which do not contain detectable amounts of HLA-DR-alpha mRNA, spontaneously transcribe the HLA-DR-alpha gene.

Cell Line↗
PubMed1984

Correlations between transcription of a yeast tRNA gene and transcription factor-DNA interactions.

A partly purified fraction from Saccharomyces cerevisiae has a RNA polymerase III transcription factor activity and contains protein which binds specifically to two internal promoter regions of RNA polymerase III-transcribed genes. The influence of ionic strength and of dimethyl sulfoxide on specific binding to a S. cerevisiae tRNAleu3 gene has been analyzed by DNase I protection (footprinting) and by nitrocellulose filter binding. The effects of these agents on binding correlate with their effects on transcription and on the stability of transcription complexes. Dimethyl sulfoxide stabilizes binding and transcription complexes against dissociation by NaCl, with 10% dimethyl sulfoxide compensating for the addition of 50-60 mM NaCl. Binding of protein in the 5' proximal part of the S. cerevisiae tRNAleu3 gene is more NaCl-sensitive than binding in the 3' proximal part.

DNA↗
PubMed1995

v-Raf activates transcription of growth-responsive promoters via GC-rich sequences that bind the transcription factor Sp1.

The serine/threonine kinase, Raf-1, is a component of intracellular signaling pathways that control responses to extracellular stimuli. Previously, we have shown that serum-induced transcription from the murine rep-3b and human mdr1 promoters is Raf-dependent and that the activated Raf kinase, v-Raf, induces transcription of mdr1 via a GC-rich element. We now demonstrate that GC-rich sequences in the rep-3b promoter are both necessary and sufficient for induction by v-Raf. The GC-rich, v-Raf-responsive elements of rep-3b and mdr1 bind the general transcription factor Sp1 in electromobility shift assays. Mutation of a minimal GC-rich element abolished inducibility by v-Raf and eliminated binding by the transcription factor Sp1. However, Sp1 binding activity following serum stimulation of quiescent NIH 3T3 cells was unchanged, suggesting that mitogenic signals may stimulate the transactivation potential of prebound Sp1.

3T3 Cells↗
PubMed1994

The ETO portion of acute myeloid leukemia t(8;21) fusion transcript encodes a highly evolutionarily conserved, putative transcription factor.

The 8;21 translocation, t(8;21)(q22;q22.3), is seen only in acute myelogenous leukemia and is characteristically associated with the M2 subtype. Subsequent to our identification of the t(8;21) breakpoint region on chromosome 21, we reported that the translocation results in the fusion of the AML1 gene on chromosome 21 with a novel gene on chromosome 8 which we called ETO (for eight twenty-one). Recently, the AML1 portion of the fusion protein has been shown to correspond to the DNA-binding and dimerization domains of the mouse gene, polyoma enhancer binding protein 2 alpha B (pebp 2 alpha B). We report here the complete sequence of the ETO portion of the fusion transcript as compiled from complementary DNAs from a t(8;21) AML patient and compare this with the ETO sequence from a mouse brain transcript. The deduced amino acid sequences are 99% identical. ETO has several features consistent with it being a transcription factor. The ETO sequence is different from the portion of PEBP 2 alpha B it replaces in the AML1/ETO fusion protein, except for their common high content of proline, serine, and threonine residues. Because neither the putative zinc fingers nor the TAF110 homology domain of ETO is present in PEBP2 alpha B, one might expect functional differences in the ability of AML1/ETO protein to affect the levels of transcription of genes normally regulated to some degree by AML1 (PEBP2 alpha B) during myeloid differentiation. The relatively high levels of ETO in developing brain suggest that it could be involved in the regulation of some aspect of neural proliferation or differentiation.

Amino Acid Sequence↗
PubMed1994

Repression of mouse mammary tumor virus transcription by a transcription factor complex. Binding of individual components to separated DNA strands.

Expression of mouse mammary tumor virus in T lymphocytes appears to be required for accession of horizontally transmitted virus to the mammary gland. Further, deletions in the long terminal repeat which relax constraints on viral transcription promote T cell lymphoma. We have identified a polypurine transcriptional repressor element (NRE1) that is deleted from viruses that induce T cell lymphoma. NRE1 binding activity in nuclear extracts proved to be related to a growth inhibitory activity that represses c-myc expression in mature B cells. Mobility shift, DNA footprinting, and UV cross-linking identified three factors that interacted preferentially with double-stranded NRE1 or the separated single strands. NRE1 binding factor (NBF) (80 kDa) bound double and upper strand NRE1, apparently in concert with NRE1 associated factor (NAF) (95 kDa), which interacted directly with DNA only on the upper strand. NRE1 lower strand binding factor (NLF) (50 kDa) cross-linked specifically to lower strand NRE1. On sucrose gradients NBF, NAF, and NLF binding activities cosedimented at 8 S, implying an in vitro association of the 50-, 80-, and 95-kDa factors which precedes DNA binding. Therefore, NRE1 appears to be the site of action of a complex transcriptional repressor comprised of at least three factors that interact differentially with each DNA strand to repress steroid hormone-induced transcription of mouse mammary tumor virus in T cells.

Animals↗
PubMed1993

Immunopurification of yeast TATA-binding protein and associated factors. Presence of transcription factor IIIB transcriptional activity.

The TATA-binding proteins (TBP) from both human and Drosophila have been shown to exist in various distinct multiprotein complexes that are required, respectively, for transcription by all three RNA polymerases. In contrast, in vitro biochemical analyses have suggested that yeast TBP exists as a monomeric 27-kDa protein free in solution. We have examined the oligomerization state of yeast TBP and report here that yeast TBP, like human and Drosophila TBPs, is also stably associated with other proteins in vitro. Using anti-TBP antibodies we have immunopurified yeast TBP and associated factors (TBP-associated factors or TAFs). When this fraction was analyzed by SDS-polyacrylamide gel electrophoresis, polypeptides of approximate relative molecular size ranging from 170 to 60 kDa are prominently represented. Immunoblot analysis revealed that one of these TAFs, TAF70, corresponds to BRF1/TDS4/PCF4, a subunit of transcription factor (TF) IIIB. Furthermore, this highly purified TAF fraction can reconstitute polymerase III transcription when supplemented with purified RNA polymerase III and TFIIIC. Our data indicate that our TAF fraction contains TFIIIB transcription factor activity and that all the subunits of yeast TFIIIB are stably complexed with TBP.

Base Sequence↗
PubMed1993

Interleukin-2-dependent transcriptional and post-transcriptional regulation of transferrin receptor mRNA.

Interleukin-2 (IL-2) controls the proliferation of the murine T cell line B6.1 and induces transferrin receptor (TfR) mRNA steady-state levels 50-fold when added to arrested, IL-2-deprived cells. In addition, TfR mRNA is post-transcriptionally regulated by intracellular iron. Low iron levels activate a cytoplasmic RNA-binding protein, called iron regulatory factor (IRF) or iron-responsive element-binding protein, which coordinately stabilizes TfR mRNA and inhibits ferritin mRNA translation. Since ferritin expression is known to be modulated by cytokines, we decided to investigate the mechanism by which IL-2 activates TfR gene expression in B6.1 cells. Induction by IL-2 of both nuclear and cytoplasmic TfR RNA was compared with run-on transcription rates in isolated nuclei. The results revealed a 3-fold increase in TfR gene transcription and a 6-fold rise in nuclear TfR RNA reaching its steady-state level within 2 h. The main accumulation of mature mRNA in the cytoplasm occurred after 6 h in parallel with the activation of IRF. However, stimulation of IRF binding activity by the iron chelator desferrioxamine, in the absence of IL-2, failed to induce TfR mRNA. Moreover, deprivation of growing B6.1 cells of IL-2 resulted in cell arrest and a rapid decay of TfR mRNA, which was not prevented by the activation of IRF with desferrioxamine. TfR mRNA stabilization appears, therefore, to depend on IL-2. We conclude that TfR mRNA expression is controlled by at least three steps at the onset of cell proliferation: (i) the growth factor-dependent activation of transcription; (ii) mRNA stabilization by IRF in the cytoplasm; and (iii) an additional IL-2-dependent activity which prevents TfR mRNA degradation. Our results indicate that expression of TfR, like ferritin, is controlled by both iron and cytokines.

Animals↗
PubMed1996

Expression of thyroid transcription factor 1 gene can be regulated at the transcriptional and posttranscriptional levels.

The complete structure of the gene for thyroid transcription factor 1 (TTF-1), both in rats and humans, has been determined. The rat TTF-1 gene shows three transcriptional start sites and contains two introns, one of which is alternatively spliced. Nuclear run-on and transient transfection experiments indicate that TTF-1 gene expression can be controlled at different levels. Using thyroid and nonthyroid cell lines, it can be shown that transcriptional mechanisms are involved in controlling thyroid-specific expression of the TTF-1 gene. In contrast, in thyroid cells expressing an activated Ki-ras oncogene, the steady-state level of TTF-1 mRNA is greatly reduced, while transcription of the TTF-1 gene is only moderately affected, suggesting that the accumulation of TTF-1 mRNA can be regulated by a posttranscriptional, Ras-sensitive mechanism.

Animals↗
PubMed1996

Transcriptional and post-transcriptional regulation of interleukin-8.

Steady-state mRNA for interleukin (IL) 8 persists significantly longer than mRNA for tumor necrosis factor (TNF)-alpha in lipopolysaccharide (LPS) stimulated human whole blood. Nuclear run-ons demonstrated consistent levels of transcriptional activity of the IL-8 gene at 2 and 26 hours after LPS stimulation when compared with the rapid induction and arrest of the TNF-alpha gene. Inhibition of cellular transcription with actinomycin D added at 2 hours after LPS resulted in the substantial decrease of both IL-8 and TNF-alpha mRNAs, demonstrating half-lives of 4.6 and 2.3 hours, respectively. In contrast, inhibition of transcription at 23 hours after LPS revealed extremely stable IL-8 mRNA with a half-life of > 10 hours. The half-life of beta-actin in the same actinomycin-D-treated samples did not vary significantly from the half-life calculated at the 2-hour time point (5.5 hours versus 5.6 hours), indicating that the observed IL-8 mRNA stability was not an artifact of the system. Both IL-8 and TNF-alpha protein levels decreased when actinomycin D was added 2 hours after LPS stimulation. However, no effect in IL-8 protein levels was evident when actinomycin D was added at 23 hours after LPS. These results demonstrate that IL-8 mRNA stability is controlled at both the transcriptional and posttranscriptional levels of gene regulation.

Humans↗
PubMed1997

Transcriptional and post-transcriptional regulation of LDL receptor gene expression in PMA-treated THP-1 cells by LDL-containing immune complexes.

We have previously shown that uptake of low density lipoprotein-containing immune complexes (LDL-IC) by human monocyte-derived macrophages led to the transformation of these cells into foam cells and induced a paradoxical increase in receptor-mediated binding of 125I-labeled LDL due to an increase in the number of LDL receptors (LDL-R). The same metabolic changes are also observed in PMA-treated THP-1 cells after incubation for 2 h with 150 microg/ml of immune complexes containing either native, oxidized (ox), or malondialdehyde (mda) LDL. After stimulation, PMA-treated THP-1 cells showed not only a 40-fold increase in 125I-labeled LDL binding but also a 40-fold increase in the immunoreactive LDL-R protein, confirming that the increase in LDL binding is due to an increase LDL-R number. In this study we have investigated, in PMA-treated THP-1 cells, the regulatory mechanism(s) responsible for the increased receptor-mediated binding of LDL induced by LDL-IC. By Northern blot and nuclear run-on analysis we have shown transcriptional activation of the LDL-R gene with a 7-fold increase in the LDL-R mRNA level in LDL-IC stimulated cells. Due to the marked difference between the increase in LDL-R mRNA and LDL-R protein, we estimated LDL-R mRNA stability using a inhibitor chase method and have shown that LDL-IC did not alter the LDL-R mRNA stability in THP-1 cells. We have also demonstrated, using cycloheximide as a inhibitor of protein synthesis, that the marked increase in LDL-R protein observed in LDL-IC-stimulated THP-1 cells resulted from de novo synthesis of LDL-R protein. To determine whether the increase in transcriptional activity of the LDL-R gene was secondary to changes in the cholesterol regulatory pool we performed experiments in which the cell cholesterol content was modified by the addition of either 25-hydroxycholesterol and mevalonate or inhibitors of ACAT activity (SA-58035 and progesterone). These experiments showed that the enhanced LDL-R expression was not affected by the addition of any of the above compounds. In conclusion, LDL-IC induced both transcriptional and post-transcriptional activation of the LDL-R gene in PMA-treated THP-1 cells and this induction was independent of the free cholesterol content of these cells.

Antigen-Antibody Complex↗
PubMed2000

Transcription of the catalytic 180-kDa subunit gene of mouse DNA polymerase alpha is controlled by E2F, an Ets-related transcription factor, and Sp1.

We have isolated a genomic DNA fragment spanning the 5'-end of the gene encoding the catalytic subunit of mouse DNA polymerase alpha. The nucleotide sequence of the upstream region was G/C-rich and lacked a TATA box. Transient expression assays in cycling NIH 3T3 cells demonstrated that the GC box of 20 bp (at nucleotides -112/-93 with respect to the transcription initiation site) and the palindromic sequence of 14 bp (at nucleotides -71/-58) were essential for basal promoter activity. Electrophoretic mobility shift assays showed that Sp1 binds to the GC box. We also purified a protein capable of binding to the palindrome and identified it as GA-binding protein (GABP), an Ets- and Notch-related transcription factor. Transient expression assays in synchronized NIH 3T3 cells revealed that three variant E2F sites near the transcription initiation site (at nucleotides -23/-16, -1/+7 and +17/+29) had no basal promoter activity by themselves, but were essential for growth-dependent stimulation of the gene expression. These data indicate that E2F, GABP and Sp1 regulate the gene expression of this principal replication enzyme.

3T3 Cells↗
PubMed2000

Isolation of a novel family of C(2)H(2) zinc finger proteins implicated in transcriptional repression mediated by chicken ovalbumin upstream promoter transcription factor (COUP-TF) orphan nuclear receptors.

Two novel and related C(2)H(2) zinc finger proteins that are highly expressed in the brain, CTIP1 and CTIP2 (COUP TF-interacting proteins 1 and 2, respectively), were isolated and shown to interact with all members of the chicken ovalbumin upstream promoter transcription factor (COUP-TF) subfamily of orphan nuclear receptors. The interaction of CTIP1 with ARP1 was studied in detail, and CTIP1 was found to harbor two independent ARP1 interaction domains, ID1 and ID2, whereas the putative AF-2 of ARP1 was required for interaction with CTIP1. CTIP1, which exhibited a punctate staining pattern within the nucleus of transfected cells, recruited cotransfected ARP1 to these foci and potentiated ARP1-mediated transcriptional repression of a reporter construct. However, transcriptional repression mediated by ARP1 acting through CTIP1 did not appear to involve recruitment of a trichostatin A-sensitive histone deacetylase(s) to the template, suggesting that this repression pathway may be distinct from that utilized by several other nuclear receptors.

Amino Acid Sequence↗