Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Alveolar rhabdomyosarcoma (ARMS) is characterized cytogenetically by a t(2;13)(q35;q14) chromosomal translocation involving two transcription factor genes: PAX3 and FKHR. ARMS cells express a PAX3-FKHR fusion protein containing the complete N-terminal, DNA-binding domain of PAX3 and the C-terminus of FKHR. Recently we demonstrated that PAX3-FKHR is a more potent transcriptional activator than PAX3 despite impaired binding to canonical PAX3 binding sites. Therefore, we propose that the gene fusion results in switching of PAX3 and FKHR transactivation domains with distinct structure, potency or function. To compare the PAX3 and putative PAX3-FKHR transactivation domains, we fused C-terminal test fragments to the heterologous GAL4 DNA-binding domain and tested activation of a reporter gene co-transfected into four cell types. GAL4-PAX3 and GAL4-PAX3-FKHR were found to be potent activators exhibiting different concentration-dependent transactivation profiles and distinct structural motifs. Deletion mapping demonstrated essential acidic and/or serine/threonine-rich domains in the extreme 3' ends of their respective coding regions and positive modifying elements in adjacent 5' sequences. These data demonstrate that PAX3 and PAX3-FKHR contain structurally distinct transcriptional activation domains and suggest that a consequent difference in function is important for oncogenesis.
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PMID:Wild type PAX3 protein and the PAX3-FKHR fusion protein of alveolar rhabdomyosarcoma contain potent, structurally distinct transcriptional activation domains. 762 19

Alveolar rhabdomyosarcomas are pediatric solid tumors with a hallmark cytogenetic abnormality: translocation of chromosomes 2 and 13 [t(2;13) (q35;q14)]. The genes on each chromosome involved in this translocation have been identified as the transcription factor-encoding genes PAX3 and FKHR. The NH2-terminal paired box and homeodomain DNA-binding domains of PAX3 are fused in frame to COOH-terminal regions of the chromosome 13-derived FKHR gene, a novel member of the forkhead DNA-binding domain family. To determine the role of the fusion protein in transcriptional regulation and oncogenesis, we identified the PAX3-FKHR fusion protein and characterized its function(s) as a transcription factor relative to wild-type PAX3. Antisera specific to PAX3 and FKHR were developed and used to examine PAX3 and PAX3-FKHR expression in tumor cell lines. Sequential immunoprecipitations with anti-PAX3 and anti-FKHR sera demonstrated expression of a 97-kDa PAX3-FKHR fusion protein in the t(2;13)-positive rhabdomyosarcoma Rh30 cell line and verified that a single polypeptide contains epitopes derived from each protein. The PAX3-FKHR protein was localized to the nucleus in Rh30 cells, as was wild-type PAX3, in t(2;13)-negative A673 cells. In gel shift assays using a canonical PAX binding site (e5 sequence), we found that DNA binding of PAX3-FKHR was significantly impaired relative to that of PAX3 despite the two proteins having identical PAX DNA-binding domains. However, the PAX3-FKHR fusion protein was a much more potent transcriptional activator than PAX3 as determined by transient cotransfection assays using e5-CAT reporter plasmids. The PAX3-FKHR protein may function as an oncogenic transcription factor by enhanced activation of normal PAX3 target genes.
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PMID:The PAX3-FKHR fusion protein created by the t(2;13) translocation in alveolar rhabdomyosarcomas is a more potent transcriptional activator than PAX3. 786 45

Rhabdomyosarcoma cells express the myogenic helix-loop-helix proteins of the MyoD family but do not differentiate into skeletal muscle cells. Gel shift and transient transfection assays revealed that MyoD in the rhabdomyosarcoma cells was capable of binding DNA but was relatively nonfunctional as a transcriptional activator. Heterokaryon formation with fibroblasts resulted in the restoration of transcriptional activation by MyoD and the differentiation of the rhabdomyosarcoma cells into skeletal muscle cells. These results suggest that rhabdomyosarcomas are deficient in a factor required for MyoD activity.
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PMID:Deficiency in rhabdomyosarcomas of a factor required for MyoD activity and myogenesis. 838 79

Pediatric alveolar rhabdomyosarcoma is characterized by a chromosomal translocation that fuses parts of the PAX3 and FKHR genes. PAX3 codes for a transcriptional regulator that controls developmental programs, and FKHR codes for a forkhead-winged helix protein, also a likely transcription factor. The PAX3-FKHR fusion product retains the DNA binding domains of the PAX3 protein and the putative activator domain of the FKHR protein. The PAX3-FKHR protein has been shown to function as a transcriptional activator. Using the RCAS retroviral vector, we have introduced the PAX3-FKHR gene into chicken embryo fibroblasts. Expression of the PAX3-FKHR protein in these cells leads to transformation: the cells become enlarged, grow tightly packed and in multiple layers, and acquire the ability for anchorage-independent growth. This cellular transformation in vitro will facilitate studies on the mechanism of PAX3-FKHR-induced oncogenesis.
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PMID:The hybrid PAX3-FKHR fusion protein of alveolar rhabdomyosarcoma transforms fibroblasts in culture. 879 Apr 12

The t(2;13) chromosomal translocation occurs at a high frequency in alveolar rhabdomyosarcoma, a common pediatric tumor of muscle. This translocation results in the production of a chimeric fusion protein derived from two developmentally regulated transcription factors, PAX3 and FKHR. The two DNA binding modules, the paired domain and the homeodomain, of PAX3 are fused in frame to the transactivation domain of FKHR. Previously, tumor-specific PAX3-FKHR has been shown to bind to DNA sequences normally recognized by wild-type PAX3 and to exhibit relatively enhanced transcriptional activity. The DNA binding sites used to demonstrate that PAX3-FKHR is a more potent transcriptional activator than PAX3 have included recognition sequences for the paired domain of PAX3. In this report, we demonstrate the ability of PAX3-FKHR to activate the product of a growth control gene, platelet-derived growth factor alpha receptor (PDGFalphaR), by recognizing a paired-type homeodomain binding site located in the PDGFalphaR promoter. PAX3 alone cannot mediate transcriptional activation of this promoter under the conditions tested. This provides the first evidence that chromosomal translocation results in altered target gene specificity of PAX3-FKHR and suggests a transcriptional target that may play a significant role in oncogenic activity and rhabdomyosarcoma development.
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PMID:Tumor-specific PAX3-FKHR transcription factor, but not PAX3, activates the platelet-derived growth factor alpha receptor. 963 96

The 2;13 chromosomal translocation in alveolar rhabdomyosarcoma generates the chimeric protein PAX3-FKHR, which is a powerful transcriptional activator. We hypothesize that PAX3-FKHR regulates downstream effector genes involved in rhabdomyosarcoma tumorigenesis. We evaluated alterations in expression of MET and neural cell adhesion molecule that were proposed previously as downstream targets of wild-type PAX3. We used a myogenic tumor cell culture system and rhabdomyosarcoma tumor specimens to assess candidate gene expression in relationship to various PAX3-FKHR expression levels. We demonstrate that the expression of MET, but not neural cell adhesion molecule, correlates significantly with PAX3-FKHR expression. These findings indicate that MET, which encodes a receptor involved in growth and motility signaling, is a downstream target of PAX3-FKHR in alveolar rhabdomyosarcoma.
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PMID:Up-regulation of MET but not neural cell adhesion molecule expression by the PAX3-FKHR fusion protein in alveolar rhabdomyosarcoma. 972 57

Alveolar rhabdomyosarcoma (ARMS) is an aggressive pediatric soft tissue tumor with striated muscle differentiation. Chromosomal studies of these tumors identified 2;13 and 1;13 translocations. Using physical mapping and cloning strategies, we determined that t(2;13) and t(1;13) rearrange PAX3 and PAX7, which encode members of the paired box transcription factor family, and juxtapose these genes with FKHR, which encodes a novel member of the fork head transcription factor family. These translocations result in chimeric transcripts consisting of 5' PAX3 or PAX7 exons fused to 3' FKHR exons, which encode fusion proteins containing the PAX3 or PAX7 DNA-binding domain and the COOH-terminal FKHR transcriptional activation domain. In transfection studies, the PAX3-FKHR fusion activates transcription of reporter genes containing PAX DNA-binding sites, and is 10-100-fold more potent as a transcriptional activator than is wild-type PAX3. This increased function results from the insensitivity of the COOH-terminal FKHR activation domain to the inhibitory effects of NH2-terminal PAX3 domains. In addition to functional alterations, our studies demonstrated PAX3-FKHR and PAX7-FKHR overexpression resulting from two distinct mechanisms, increased transcription of PAX3-FKHR by a copy number-independent mechanism, and gene amplification of PAX7-FKHR. These findings indicate that the genetic changes in these tumors result in high levels of chimeric transcription factors that are hypothesized to inappropriately activate transcription of genes with PAX DNA-binding sites and thereby induce tumorigenic behavior. The differences in overexpression strategies suggest important differences between the mechanisms for regulating PAX3 and PAX7 expression. These differences extend to the phenotypic level, at which clinical differences have been found between the two ARMS subtypes: PAX7-FKHR tumors more often occur as localized lesions in the extremities of younger patients and are associated with longer event-free survival as compared to PAX3-FKHR tumors. Therefore, the clinical heterogeneity within the ARMS category is associated with genetic heterogeneity. Further analysis of the transcriptional function, regulation of expression, and phenotypic effects will help to elucidate the action of these fusion products and the biological basis of the clinical heterogeneity.
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PMID:The role of chimeric paired box transcription factors in the pathogenesis of pediatric rhabdomysarcoma. 1019 85

The t(2;13) chromosomal translocation in alveolar rhabdomyosarcoma tumors (ARMS) creates an oncogenic transcriptional activator by fusion of PAX3 DNA binding motifs to a COOH-terminal activation domain derived from the FKHR gene. The dominant oncogenic potential of the PAX3-FKHR fusion protein is dependent on the FKHR activation domain. We have fused the KRAB repression module to the PAX3 DNA binding domain as a strategy to suppress the activity of the PAX3-FKHR oncogene. The PAX3-KRAB protein bound PAX3 target DNA sequences and repressed PAX3-dependent reporter plasmids. Stable expression of the PAX3-KRAB protein in ARMS cell lines resulted in loss of the ability of the cells to grow in low-serum or soft agar and to form tumors in SCID mice. Stable expression of a PAX3-KRAB mutant, which lacks repression function, or a KRAB protein alone, lacking a PAX3 DNA binding domain, failed to suppress the ARMS malignant phenotype. These data suggest that the PAX3-KRAB repressor functions as a DNA-binding-dependent suppressor of the transformed phenotype of ARMS cells, probably via competition with the endogenous PAX3-FKHR oncogene and repression of target genes required for ARMS tumorigenesis. The engineered repressor approach that directs a transcriptional repression domain to target genes deregulated by the PAX3-FKHR oncogene may be a useful strategy to identify the target genes critical for ARMS tumorigenesis.
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PMID:An engineered PAX3-KRAB transcriptional repressor inhibits the malignant phenotype of alveolar rhabdomyosarcoma cells harboring the endogenous PAX3-FKHR oncogene. 1086 59

We have applied engineered transcriptional repressors to specifically inhibit disease gene-activated pathways in oncogenesis. We have demonstrated that synthetic repressors combining PAX3 DNA binding domains with different repression domains, KRAB or SNAG, are able to specifically inhibit malignant growth and suppress tumorigenesis in alveolar rhabdomyosarcoma tumor cells transformed by the translocation-derived chimeric transcriptional activator, PAX3-FKHR. We discuss the potential applications of the engineered repressor strategy that relate to target gene analysis, mechanisms of repression, cell regulation, and possible anti-viral and cancer therapy.
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PMID:Regulating the neoplastic phenotype using engineered transcriptional repressors. 1116 87

Glucose-6-phosphatase catalyzes the terminal step in the gluconeogenic and glycogenolytic pathways. In HepG2 cells, the maximum repression of basal glucose-6-phosphatase catalytic subunit (G6Pase) gene transcription by insulin requires two distinct promoter regions, designated A (located between -231 and -199) and B (located between -198 and -159), that together form an insulin response unit. Region A binds hepatocyte nuclear factor-1, which acts as an accessory factor to enhance the effect of insulin, mediated through region B, on G6Pase gene transcription. We have previously shown that region B binds the transcriptional activator FKHR (FOXO1a) in vitro. Chromatin immunoprecipitation assays demonstrate that FKHR also binds the G6Pase promoter in situ and that insulin inhibits this binding. Region B contains three insulin response sequences (IRSs), designated IRS 1, 2, and 3, that share the core sequence T(G/A)TTTT. However, detailed analyses reveal that these three G6Pase IRSs are functionally distinct. Thus, FKHR binds IRS 1 with high affinity and IRS 2 with low affinity but it does not bind IRS 3. Moreover, in the context of the G6Pase promoter, IRS 1 and 2, but not IRS 3, are required for the insulin response. Surprisingly, IRS 3, as well as IRS 1 and IRS 2, can each confer an inhibitory effect of insulin on the expression of a heterologous fusion gene, indicating that, in this context, a transcription factor other than FKHR, or its orthologs, can also mediate an insulin response through the T(G/A)TTTT motif.
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PMID:The three insulin response sequences in the glucose-6-phosphatase catalytic subunit gene promoter are functionally distinct. 1255 24


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