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

The Wilms' tumor suppressor gene WT1 encodes a zinc finger transcription factor, whose expression inhibits the growth of the RM1 Wilms' tumor cell line. Transient transfection of WT1 constructs into 3T3 or 293 cells results in transcriptional repression of a number of cotransfected promoters containing the early growth response gene 1 consensus sequence. We now show that WT1 has properties of a transcriptional activator in RM1 cells, an effect that may be associated with the presence of a mutated p53 gene in these cells. Stable transfection of wild-type WT1 into RM1 cells results in induction of endogenous insulin-like growth factor 2 (IGF2) but not of other previously postulated WT1-target genes. The induction of IGF2 is dramatically enhanced by WT1 mutants encoding an altered transactivation domain. We conclude that IGF2 is a potentially physiological target gene for WT1 and that its induction may contribute to the growth-stimulating effects of WT1 variants.
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PMID:WT1 induces expression of insulin-like growth factor 2 in Wilms' tumor cells. 755 24

The Wilms' tumor suppressor gene, WT1, encodes a transcription factor in the zinc finger family, which binds to GC-rich sequences and functions as a transcriptional activator or repressor. The WT1 protein plays a crucial role in urogenital development in mammals and its function is thought to be conserved during vertebrate evolution. Although accumulating evidence suggests that WT1 regulates a subset of genes including growth factor and growth factor receptor genes, little is known about regulators or signal cascades that could modulate the function of WT1. In this study, we show that the WT1 protein expressed exogenously in fibroblasts was phosphorylated in vivo, and that treatment with forskolin, which activates the cAMP-dependent protein kinase (PKA) in vivo, induced phosphorylation of additional sites in WT1. We identified the forskolin-induced phosphorylation sites as Ser-365 and Ser-393, which lie in the zinc finger domain in zinc fingers 2 and 3, respectively. PKA phosphorylated WT1 at Ser-365 and Ser-393 in vitro, as well as at additional sites, and this phosphorylation abolished the DNA-binding activity of WT1 in vitro. Using WT1 mutants in which Ser-365 and Ser-393 were mutated to Ala individually and in combination, we showed that phosphorylation of these sites was critical for inhibition of DNA binding in vivo. Thus, coexpression of the PKA catalytic subunit with wild type WT1 reduced the level of WT1 DNA-binding activity detected in nuclear extracts, and decreased transcriptional repression activity in vivo. In contrast to wild type WT1, all of the phosphorylation site mutants retained significant DNA-binding activity and repression activity in the presence of PKA. Analysis of the mutants showed that phosphorylation of Ser-365 and Ser-395 had additive inhibitory effects on WT1 DNA-binding in vivo and that phosphorylation at both sites was required for neutralization of repression activity. Therefore, we conclude that PKA modulates the activity of WT1 in vivo through phosphorylation of Ser-365 and Ser-393, which inhibits DNA binding. This in turn results in a decrease in WT1 transcriptional repression. Our findings provide the first evidence that the function of WT1 can be modulated by its phosphorylation in vivo.
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PMID:Inhibition of the DNA-binding and transcriptional repression activity of the Wilms' tumor gene product, WT1, by cAMP-dependent protein kinase-mediated phosphorylation of Ser-365 and Ser-393 in the zinc finger domain. 936 17

To gain better understanding of the molecular alterations responsible for the aggressive growth potential of epidermal growth factor receptor (EGFR)-positive breast cancers, we utilized an expression cloning strategy to seek gene products that mediate the EGF-independent growth of human breast cancer cells. A retroviral cDNA expression library was constructed from the EGFR-positive SUM-149PT cell line, and transduced into growth factor-dependent human mammary epithelial (HME) cells. Recipient cells were functionally selected for their ability to proliferate in serum-free, EGF-free medium. Library cDNAs were recovered from EGF-independent colonies by PCR amplification or by biological rescue. Clone H55a#1 contained a library insert encoding amphiregulin. This EGFR ligand was able to confer EGF independence when transduced into HME cells. SUM-149PT and H55a#1 cells overexpressed amphiregulin transcripts, and secreted moderate EGF-like activity in conditioned media, indicating a possible autocrine loop. EGFR membrane levels and constitutive phosphorylation were consistent with this hypothesis, as well as the sensitivity of the cells to an ErbB-specific kinase inhibitor. Expression of the WT1 Wilms' tumor suppressor gene, a transcriptional activator of amphiregulin, did not parallel amphiregulin transcript levels, suggesting that another factor regulates amphiregulin in SUM-149PT. Our data confirm the importance of amphiregulin in the etiology of breast cancer.
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PMID:A functional screen for genes inducing epidermal growth factor autonomy of human mammary epithelial cells confirms the role of amphiregulin. 1149 30