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 soluble fraction of nuclear proteins is a functionally significant fraction, since it has been shown that it contains ribonucleoproteins active in nuclear RNA metabolism. The aim of this work was to detect variations associated with cell proliferation, by comparing two-dimensional proteomes obtained from the soluble fractions of onion nuclei isolated from actively proliferating root meristematic cells versus nonmeristematic root cells. In particular, we have studied the physicochemical features of the major nucleolar protein NopA100, a highly phosphorylated, nucleolin-like protein. A total of 384 spots were quantified in meristematic nuclei, while only 209 were detected in nonmeristematic nuclei. The comparison of both proteomes resulted in the determination of specific spots for each proliferative state and those which were common to both cases. Furthermore, among these latter, we could discriminate quantitative differences. Interestingly, well-known nucleolar proteins, such as RNA polymerase I, B23 and the nucleolin-like protein NopA100, were significantly increased in proliferating cells. Western blots with anti-NopA100 antibody demonstrated 26 spots in the meristematic sample. All the spots detected were clustered at 100 kDa and were distributed through an isoelectric point (pI) range of 4.3-6.6. In contrast, only seven spots were found in the extract from nonmeristematic nuclei, and the pI range was shortened to 4.8-6.1. These results indicate that the state of NopA100 phosphorylation correlates with the degree of nucleolar activity, i.e. the protein is more highly phosphorylated in cycling cells. We have also analyzed the bidimensional silver staining of the nucleolar organizing region (Ag-NOR) pattern of the soluble nuclear fraction in order to identify plant cell phosphoproteins that are considered to be markers of proliferation. These experiments demonstrated that NopA100, the onion, nucleolin-like protein, is an Ag-NOR protein. In addition we found that the plant homologue of the vertebrate nucleolar phosphoprotein B23 migrated as two clusters of acidic spots, 43 and 42 kDa respectively in molecular mass. The differences between these features and those described for mammalian cells is discussed. Our results demonstrate that the use of protein fractionation procedures with functional significance and the location of candidate spots by indirect techniques are advantageous, complementary methods to random selection procedures for proteomic studies involving further mass spectrometry analysis.
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PMID:Identification of specific plant nucleolar phosphoproteins in a functional proteomic analysis. 1476 Jul 10

Tamoxifen is the primary hormonal therapy for breast cancer and is also used as a breast cancer chemopreventative agent. A major problem with tamoxifen therapy is undesirable endometrial proliferation. To identify proteins associated with the growth stimulatory effects of tamoxifen in an ER-positive model, the present study profiled total cellular and secreted proteins regulated by estradiol and selective estrogen receptor modifiers (SERMs) in the Ishikawa endometrial adenocarcinoma cell line using two-dimensional gel electrophoresis. Following 24 h incubation with 10(-8) M estradiol, 10(-7) M 4-hydroxytamoxifen, or 10(-7) M EM-652 (Acolbifene), nine proteins exhibited significant increase in expression. The proteins identified were heat shock protein 90-alpha, and -beta, heterogeneous nuclear ribonucleoprotein F, RNA polymerase II-mediating protein, cytoskeletal keratin 8, cytoskeletal keratin 18, ubiquitin-conjugating enzyme E2-18 kDa and nucleoside diphosphate kinase B. These protein profiles may serve as novel indices of SERM response and may also provide insight into novel mechanisms of SERM-mediated growth.
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PMID:Selective estrogen receptor modulator regulated proteins in endometrial cancer cells. 1514 34

An insulin-responsive element (IRE) in the rat angiotensinogen (ANG) gene promoter that binds to two nuclear proteins with apparent molecular weights of 48 and 70 kD was identified previously from rat immortalized renal proximal tubular cells (IRPTC). The present studies aimed to identify and clone the 48-kD nuclear protein and to define its action on ANG gene expression. Nuclear proteins were isolated from IRPTC and subjected to two-dimensional electrophoresis. The 48-kD nuclear protein was detected by Southwestern blotting and subsequently identified by mass spectrometry, revealing that it was identical to 46-kD heterogeneous nuclear ribonucleoprotein F (hnRNP F), a nuclear protein that binds to TATA-binding protein and associates with RNA polymerase II and also interacts with nuclear cap-binding complex. The hnRNP F cDNA was cloned from IRPTC by reverse transcriptase-PCR. Bacterially expressed recombinant hnRNP F bound to the rat ANG-IRE, as revealed by gel mobility shift assay. The addition of polyclonal antibodies against hnRNP F yielded a supershift in gel mobility. Transient transfer of sense and antisense hnRNP F cDNA in IRPTC inhibited and enhanced ANG gene expression, respectively. High glucose stimulated and insulin inhibited hnRNP F expression in IRPTC. Expression studies indicated that hnRNP F is present in the kidney, testis, liver, lung, and brain but not in the spleen. In conclusion, these studies demonstrate that hnRNP F binds to rANG-IRE and modulates renal ANG gene expression, implicating that dysregulation of hnRNP F might affect renin-angiotensin system activation and, subsequently, kidney injury in diabetes.
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PMID:Heterogenous nuclear ribonucleoprotein F modulates angiotensinogen gene expression in rat kidney proximal tubular cells. 1565 59

To investigate novel NS1-interacting proteins, we conducted a yeast two-hybrid analysis, followed by co-immunoprecipitation assays. We identified heterogeneous nuclear ribonucleoprotein F (hnRNP-F) as a cellular protein interacting with NS1 during influenza A virus infection. Co-precipitation assays suggest that interaction between hnRNP-F and NS1 is a common and direct event among human or avian influenza viruses. NS1 and hnRNP-F co-localize in the nucleus of host cells, and the RNA-binding domain of NS1 directly interacts with the GY-rich region of hnRNP-F determined by GST pull-down assays with truncated proteins. Importantly, hnRNP-F expression levels in host cells indicate regulatory role on virus replication. hnRNP-F depletion by small interfering RNA (siRNA) shows 10- to 100-fold increases in virus titers corresponding to enhanced viral RNA polymerase activity. Our results delineate novel mechanism of action by which NS1 accelerates influenza virus replication by modulating normal cellular mRNA processes through direct interaction with cellular hnRNP-F protein.
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PMID:Direct interaction of cellular hnRNP-F and NS1 of influenza A virus accelerates viral replication by modulation of viral transcriptional activity and host gene expression. 2342 46