Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The whole length of exon 11 of BRCA1 was sequenced (total 3427 bp) in 59 patients and 10 healthy female blood donors. To allow a rapid determination of the different BRCA1 alleles, a sequence-specific primer PCR method (PCR-SSP) was established and was applied to 57 additional female donors. Finally, the full-length coding region of BRCA1 was analyzed through reversed-transcriptase PCR (RT-PCR) and cDNA sequencing (total 5554 bp) in one donor with wild-type allele and 2 patients with one or two mutated alleles. By genomic DNA sequencing, 5 homozygous polymorphisms were observed in 18 patients: 2201C>T, 2430T>C, 2731C>T, 3232A>G and 3667A>G All of them were previously observed in Caucasians, Malay and Chinese, but for the first time the mutations were found in one allele (GenBank AY304547). Twenty-six patients and 4 donors were heterozygous at these 5 nucleotide positions. The remaining 15 patients and 6 donors showed a sequence identical with the standard BRCA1 gene. Combined the PCR-SSP results and in a summary, 6 of 67 (9.0 %) healthy individuals were homozygous for the mutated allele, whereas 18 of 59 (30.5 %) breast cancer patients were homozygous. A Chi-square test showed a significant correlation between homozygous mutated BRCA1 allele and breast cancer. The cDNA sequencing showed that 2 additional mutations, 4427T>C in exon 13 and 4956A>G in exon 16, were found. A new BRCA1 allele, which is BRCAI-2201T/2430C/2731T/3232G/3667G/4427C/4956G (GenBank AY751490), was found in Chinese. And the homozygote of this mutated allele may implicate a disease-association in Chinese.
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PMID:A novel frequent BRCA1 allele in Chinese patients with breast cancer. 1721 73

Estrogen receptors activate transcription in part through direct interactions with specific DNA motifs, called estrogen response elements (EREs). Here we show that the strong and sustained induction of the gene regulated in breast cancer 1 (GREB1), a gene of unknown function that has been previously suggested to play a role in the effects of estradiol on breast cancer cell proliferation (Rae, J. M., Johnson, M. D., Scheys, J. O., Cordero, K. E., Larios, J. M., and Lippman, M. E. (2005) Breast Cancer Res. Treat 92, 141-149), is mediated by binding of estrogen receptor alpha (ERalpha) to three consensus EREs spread over approximately 20 kb of upstream flanking sequences. In addition to ERalpha, coactivator SRC-3, acetylated histones and phosphorylated RNA polymerase II (P-polII) were detected on all three EREs in the presence of estrogen, while basal recruitment of ERalpha and P-polII was observed only on the proximal element. Chromatin loops were formed between each ERE and the GREB1 transcriptional start site in the presence of estrogen but not of a total antiestrogen. Furthermore, estradiol induced physical association between EREs, suggesting that these elements function as a potent multipartite enhancer to regulate GREB1 transcription.
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PMID:Regulation of GREB1 transcription by estrogen receptor alpha through a multipartite enhancer spread over 20 kb of upstream flanking sequences. 1746

Estrogen receptor-alpha (ERalpha) and its ligand estradiol play critical roles in breast cancer growth and are important therapeutic targets for this disease. Using chromatin immunoprecipitation (ChIP)-on-chip, ligand-bound ERalpha was recently found to function as a master transcriptional regulator via binding to many cis-acting sites genome-wide. Here, we used an alternative technology (ChIP cloning) and identified 94 ERalpha target loci in breast cancer cells. The ERalpha-binding sites contained both classic estrogen response elements and nonclassic binding sequences, showed specific transcriptional activity in reporter gene assay, and interacted with the key transcriptional regulators, including RNA polymerase II and nuclear receptor coactivator-3. The great majority of the binding sites were located in either introns or far distant to coding regions of genes. Forty-three percent of the genes that lie within 50 kb to an ERalpha-binding site were regulated by estradiol. Most of these genes are novel estradiol targets encoding receptors, signaling messengers, and ion binders/transporters. mRNA profiling in estradiol-treated breast cancer cell lines and tissues revealed that these genes are highly ERalpha responsive both in vitro and in vivo. Among estradiol-induced genes, Wnt11 was found to increase cell survival by significantly reducing apoptosis in breast cancer cells. Taken together, we showed novel genomic binding sites of ERalpha that regulate a novel set of genes in response to estradiol in breast cancer. Our findings suggest that at least a subset of these genes, including Wnt11, may play important in vivo and in vitro biological roles in breast cancer.
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PMID:Novel estrogen receptor-alpha binding sites and estradiol target genes identified by chromatin immunoprecipitation cloning in breast cancer. 1751 Apr 34

The transcription factor GATA-3 is required for normal mammary gland development, and its expression is highly correlated with estrogen receptor alpha (ER alpha) in human breast tumors. However, the functional role of GATA-3 in ER alpha-positive breast cancers is yet to be established. Here, we show that GATA-3 is required for estradiol stimulation of cell cycle progression in breast cancer cells. The role of GATA-3 in estradiol signaling requires the direct positive regulation of the expression of the ER alpha gene itself by GATA-3. GATA-3 binds to two cis-regulatory elements located within the ER alpha gene, and this is required for RNA polymerase II recruitment to ER alpha promoters. Reciprocally, ER alpha directly stimulates the transcription of the GATA-3 gene, indicating that these two factors are involved in a positive cross-regulatory loop. Moreover, GATA-3 and ER alpha regulate their own expression in breast cancer cells. Hence, this transcriptional coregulatory mechanism accounts for the robust coexpression of GATA-3 and ER alpha in human breast cancers. In addition, these results highlight the crucial role of GATA-3 for the response of ER alpha-positive breast cancers to estradiol. Moreover, they identify GATA-3 as a critical component of the master cell-type-specific transcriptional network including ER alpha and FoxA1 that dictates the phenotype of hormone-dependent breast cancer.
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PMID:Positive cross-regulatory loop ties GATA-3 to estrogen receptor alpha expression in breast cancer. 1761 9

Preferentially expressed antigen of melanoma (PRAME) has been described as a potential candidate for immunotherapeutic targeting. However, the prognostic and predictive relevance of PRAME in breast cancer has never been investigated. PRAME gene expression was evaluated in 103 breast tumour biopsies, using quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR). Normal breast tissue was also analysed for comparative purposes. All qRT-PCRs were performed in triplicate. Kaplan-Meier survival curves, Chi-squared and Cox Regression analyses were used to identify associations between PRAME expression and patients' clinicopathological and survival data. PRAME mRNA was detected in approximately 53% of tumour specimens and 37% of normal breast specimens. Kaplan-Meier analysis showed expression of PRAME to correlate significantly with unfavourable disease outcome for patients, in terms of both their disease-free survival (p = 0.0004) and overall survival (OS) (p = 0.0052) times from diagnosis. Multivariate analysis indicated PRAME expression to be an independent prognostic factor for shortened disease-free survival (p = 0.026) and OS (p = 0.02). Furthermore, for patients who received adjuvant chemotherapy, significantly (p = 0.0291) shorter relapse-free survival was achieved for those whose tumour expressed PRAME, compared to those that did not express this transcript. Our results suggest that PRAME mRNA expression may be a useful prognostic and predictive marker for breast cancer.
Breast Cancer Res Treat 2008 May
PMID:Prevalence and prognostic and predictive relevance of PRAME in breast cancer. 1762 86

The estrogen receptor (ER) binds to estrogen-responsive elements (EREs) to activate gene transcription. The best characterized EREs are located in proximal gene promoters, but recent data indicate that only a minority of ER binding sites lie within proximal promoter regions. GREB1 (gene regulated by estrogen in breast cancer 1) is an ER target gene that regulates estrogen-induced proliferation in breast cancer cells. We identified three consensus EREs, located at -21.2, -9.5, and -1.6 kb upstream of the closest GREB1a transcription start site that appear to mediate long-range GREB1 gene activation by ER. All three ERE sites nucleate ER, steroid receptor coactivator-3 (SRC-3), and RNA polymerase II (Pol II) and undergo histone acetylation in response to estradiol. Estrogen-stimulated ER binding at all three EREs was cyclic and synchronous. SRC-3 and Pol II recruitment to all three EREs was activated by estrogen but not tamoxifen. In contrast, estrogen stimulated only Pol II and not ER or SRC-3 recruitment to the GREB1 core promoter regions. Long-range histone acetylation, centered on the three ERE motifs and the GREB1 core promoters, was observed in response to estrogen but not to tamoxifen. These data suggest that estrogen-stimulated GREB1 transcription may involve coordinated ER binding to all three distal consensus ERE motifs. Long-range activation by ER acting at multiple EREs may be more common than previously appreciated.
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PMID:Long-range activation of GREB1 by estrogen receptor via three distal consensus estrogen-responsive elements in breast cancer cells. 1766 87

Cyclooxygenase enzymes play an important role in carcinogenesis, and increased expression of cyclooxygenase enzymes has been reported in cancers arising at a number of different sites. Most, if not all of these actions are thought to be mediated by prostaglandin E2 (PGE2). The actions of PGE2 are mediated via four main prostanoid receptors, designated EP1, EP2, EP3 and EP4, based on their different pharmacological properties and secondary messenger pathways. Recently, expression of EP1 has been reported in rat mammary gland and the inhibition of this receptor has been documented to have chemopreventive effect in this animal model. EP1 has also been shown to decrease the incidence of colon cancer in mouse models. In this study, we analysed the expression of EP1 in normal and malignant breast tissues. Expression of EP1 was analysed in breast (benign and cancer) cell lines by reverse-transcriptase polymerase chain reaction and by western blot analyses. Expression was also analysed by immunohistochemistry in normal breast tissues and in 89 cases of breast cancer. Semiquantitative analysis of the staining was performed. The data were compared with and correlated with other prognostic factors like tumour size, tumour grade, lymph node status, oestrogen receptor, progesterone receptor (PR), HER2/neu and cyclooxygenase-2. EP1 expression was demonstrated in human breast cancer by immunohistochemistry. Expression of EP1 was seen both in the cytoplasm and/or in the nuclear membrane in majority of cases. Nuclear EP1 expression correlated with PR (P=0.032) and inversely with node positivity (P=0.025). However, EP1 expression did not correlate with expression of cyclooxygenase-2 (P=0.059). Expression of EP1 is frequently seen in human breast cancers. Nuclear expression of EP1 correlates with good prognosis markers like node negative status and PR expression.
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PMID:Prostanoid receptor EP1 expression in breast cancer. 1790 15

BRCA1 has been implicated in numerous DNA repair pathways that maintain genome integrity, however the function responsible for its tumor suppressor activity in breast cancer remains obscure. To identify the most highly conserved of the many BRCA1 functions, we screened the evolutionarily distant eukaryote Saccharomyces cerevisiae for mutants that suppressed the G1 checkpoint arrest and lethality induced following heterologous BRCA1 expression. A genome-wide screen in the diploid deletion collection combined with a screen of ionizing radiation sensitive gene deletions identified mutants that permit growth in the presence of BRCA1. These genes delineate a metabolic mRNA pathway that temporally links transcription elongation (SPT4, SPT5, CTK1, DEF1) to nucleopore-mediated mRNA export (ASM4, MLP1, MLP2, NUP2, NUP53, NUP120, NUP133, NUP170, NUP188, POM34) and cytoplasmic mRNA decay at P-bodies (CCR4, DHH1). Strikingly, BRCA1 interacted with the phosphorylated RNA polymerase II (RNAPII) carboxy terminal domain (P-CTD), phosphorylated in the pattern specified by the CTDK-I kinase, to induce DEF1-dependent cleavage and accumulation of a RNAPII fragment containing the P-CTD. Significantly, breast cancer associated BRCT domain defects in BRCA1 that suppressed P-CTD cleavage and lethality in yeast also suppressed the physical interaction of BRCA1 with human SPT5 in breast epithelial cells, thus confirming SPT5 as a relevant target of BRCA1 interaction. Furthermore, enhanced P-CTD cleavage was observed in both yeast and human breast cells following UV-irradiation indicating a conserved eukaryotic damage response. Moreover, P-CTD cleavage in breast epithelial cells was BRCA1-dependent since damage-induced P-CTD cleavage was only observed in the mutant BRCA1 cell line HCC1937 following ectopic expression of wild type BRCA1. Finally, BRCA1, SPT5 and hyperphosphorylated RPB1 form a complex that was rapidly degraded following MMS treatment in wild type but not BRCA1 mutant breast cells. These results extend the mechanistic links between BRCA1 and transcriptional consequences in response to DNA damage and suggest an important role for RNAPII P-CTD cleavage in BRCA1-mediated cancer suppression.
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PMID:Yeast screens identify the RNA polymerase II CTD and SPT5 as relevant targets of BRCA1 interaction. 1819 58

Steroid hormone receptors regulate gene expression, interacting with target DNA sequences but also activating cytoplasmic signaling pathways. Using the human 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) gene as a model, we have investigated the contributions of both effects on a human progesterone-responsive promoter in breast cancer cells. Chromatin immunoprecipitation has identified two different mechanisms of hormone-induced progesterone receptor (PR) recruitment to the 11beta-HSD2 promoter: (i) direct PR binding to DNA at the proximal promoter, abrogated when PR contains a mutated DNA binding domain (DBD), and (ii) STAT5A (signal transducer and activator of transcription 5A)-mediated recruitment of PR to an upstream distal region, impaired by AG490, a JAK/STAT pathway inhibitor. The JAK/STAT inhibitor, as well as expression of dominant-negative STAT5A, impairs hormone induction of 11beta-HSD2. On the other hand, the DBD-mutated PR fully supports 11beta-HSD2 expression. These results, along with data from a deletion analysis, indicate that the distal region is crucial for hormone regulation of 11beta-HSD2. We show active RNA polymerase II tracking from the distal region upon PR and STAT5A binding, concomitant with synthesis of noncoding, hormone-dependent RNAs, suggesting that this region works as a hormone-dependent transcriptional enhancer. In conclusion, coordination of PR transcriptional effects and cytoplasmic signaling activation, in particular the JAK/STAT pathway, are critical in regulating progestin-induced endogenous 11beta-HSD2 gene expression in breast cancer cells. This is not unique to this promoter, as AG490 also alters the expression of other progesterone-regulated genes.
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PMID:Progesterone induction of the 11beta-hydroxysteroid dehydrogenase type 2 promoter in breast cancer cells involves coordinated recruitment of STAT5A and progesterone receptor to a distal enhancer and polymerase tracking. 1837 98

The transcription factor CCAAT/enhancer binding protein-alpha (C/EBP alpha) is involved in the control of cell differentiation and proliferation, and has been suggested to act as a tumor suppressor in several cancers. By using microarray analysis, we have previously shown that hypoxia and estrogen down-regulate C/EBP alpha mRNA in T-47D breast cancer cells. Here, we have examined the mechanism by which the down-regulation by hypoxia takes place. Using the specific RNA polymerase II inhibitor 5,6-dichlorobenzimidazole-1-beta-D-ribofuranoside, the mRNA stability was analyzed under normoxia or hypoxia by quantitative reverse transcription-PCR. Hypoxia reduced the half-life of C/EBP alpha mRNA by approximately 30%. C/EBP alpha gene promoter studies indicated that hypoxia also repressed the transcription of the gene and identified a hypoxia-responsive element (-522; -527 bp), which binds to hypoxia-inducible factor (HIF)-1 alpha, as essential for down-regulation of C/EBP alpha transcription in hypoxia. Immunocytochemical analysis showed that C/EBP alpha was localized in the nucleus at 21% O(2), but was mostly cytoplasmic under 1% O(2). Knockdown of HIF-1 alpha by RNAi restored C/EBP alpha to normal levels under hypoxic conditions. Immunohistochemical studies of 10 tumor samples did not show any colocalization of C/EBP alpha and glucose transporter 1 (used as a marker for hypoxia). Taken together, these results show that hypoxia down-regulates C/EBP alpha expression in breast cancer cells by several mechanisms, including transcriptional and posttranscriptional effects. The down-regulation of C/EBP alpha in hypoxia is mediated by HIF-1.
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PMID:Hypoxia down-regulates CCAAT/enhancer binding protein-alpha expression in breast cancer cells. 1838 21


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