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)

Epstein-Barr virus (EBV) is a ubiquitous human gammaherpesvirus associated with a wide spectrum of malignant neoplasms. Expression of latent (growth transformation-associated) EBV genes is host cell specific. Transcripts for EBV-encoded nuclear antigens (EBNAs) are initiated at one of the alternative promoters: Wp, Cp (for EBNA1-6), or Qp (for EBNA1 only). Wp is active shortly after EBV infection of human B cells in vitro but is progressively methylated and silenced in established lymphoblastoid cell lines (LCLs). In parallel Cp, an unmethylated, lymphoid-specific promoter is switched on. In contrast, Cp is methylated and silent in Burkitt's lymphoma (BL) cell lines, which keep the phenotype of BL biopsy cells (group I BL lines). These cells use Qp for the initiation of EBNA1 messages. Qp is unmethylated both in group I BLs (Qp on) and in LCLs (Qp off). Thus, DNA methylation does not play a role in silencing Qp. In LCLs and nasopharyngeal carcinoma (NPC) cells, transcripts for latent membrane protein 1 (LMP1) are initiated from LMP1p, a promoter regulated by CpG methylation. LMPlp is silent in group I BL lines but can be activated by demethylating agents. Promoter silencing by CpG methylation involves both direct interference with transcription factor binding (Wp, Cp) and indirect mechanisms involving the recruitment of histone deacetylases (LMPlp). A dyad symmetry sequence(DS) within oriP (the latent origin of EBV replication) and intragenic RNA polymerase III control regions of EBER 1 and 2 transcription units are invariably unmethylated in EBV-carrying cells.
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PMID:Host cell-dependent expression of latent Epstein-Barr virus genomes: regulation by DNA methylation. 1458 72

There have been few studies regarding cancer progression from differentiated thyroid carcinoma to the undifferentiated one. To examine the possible involvement of Epstein-Barr virus (EBV) in this progression, 10 papillary carcinomas and 11 undifferentiated carcinomas were subjected to mRNA in situ hybridization, indirect immunofluorescence staining, polymerase chain reaction (PCR), and reverse-transcriptase PCR. mRNA in situ hybridization using a BamHIW probe revealed signals in all of the examined samples, although the signal strength was weaker in the papillary carcinomas than in the undifferentiated carcinomas. EBV nuclear antigen-2 (EBNA2) in situ hybridization produced almost the same results; however, the signals were detected less frequently in the papillary carcinomas. Indirect immunofluorescence using anti-EBNA2, anti-latent membrane protein-1 (LMP1), and anti-BZLF1 antibodies also showed positive results with high frequency and with more prominent fluorescence in undifferentiated carcinomas than in papillary carcinomas. An examination of thyroid carcinoma cell lines also confirmed these findings. EBV infected all of the thyroid carcinomas irrespective of the degree of pathological differentiation. The expression of EBV, especially of EBNA2 and LMP1 (both of which are oncogene products of EBV), was stronger in the undifferentiated carcinomas than in the papillary carcinomas. These results suggest that increased expression of EBV may be involved in the progression of thyroid papillary carcinoma to undifferentiated carcinoma.
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PMID:Expression of Epstein-Barr virus in thyroid carcinoma correlates with tumor progression. 1465 19

The quest for an infectious agent that may account for cases of Hodgkin's disease (HD) especially in young adults has proven vain until lately. We have recently reported findings that suggested the presence of measles virus (MV) antigens and MV RNA in the tissues of patients with HD. Support for an association between MV and HD has been provided by recent epidemiological findings relating the occurrence of HD to exposure to measles in pregnancy and the perinatal period. We now present further evidence of this putative association based on immunohistochemical, reverse transcriptase-polymerase chain reaction (RT-PCR) and in situ hybridisation studies (ISH) on HD tissues. Biopsies from 82 (54.3%) of our cohort of 154 patients showed a positive immunostain with at least two of the anti-measles antibodies used. Latent membrane protein-1 immunostaining for Epstein-Barr virus was positive in 46 (31.1%) of the patients examined. Reverse transcriptase-PCR and ISH for measles RNA were positive in seven and 10 of 28 patients, respectively. Preliminary clinicopathological associations between MV and HD are noted in this study, but no causal relationship can be claimed at this stage.
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PMID:Measles virus: evidence of an association with Hodgkin's disease. 1522 78

The phage shock protein operon (pspABCDE) of Escherichia coli is strongly up-regulated in response to overexpression of the filamentous phage secretin protein IV (pIV) and by many other stress conditions including defects in protein export. PspA has an established role in maintenance of the proton-motive force of the cell under stress conditions. Here we present evidence for a new member of the phage shock response in E. coli. Using transcriptional profiling, we show that the synthesis of pIV in E. coli leads to a highly restricted response limited to the up-regulation of the psp operon genes and yjbO. The psp operon and yjbO are also up-regulated in response to pIV in Salmonella enterica serovar Typhimurium. yjbO is a highly conserved gene found exclusively in bacteria that contain a psp operon but is physically unlinked to the psp operon. yjbO encodes a putative inner membrane protein that is co-controlled with the psp operon genes and is predicted to be an effector of the psp response in E. coli. We present evidence that yjbO expression is driven by sigma(54)-RNA polymerase, activated by PspF and integration host factor, and negatively regulated by PspA. PspF specifically regulates only members of the PspF regulon: pspABCDE and yjbO. We found that increased expression of YjbO results in decreased motility of bacteria. Because yjbO is co-conserved and co-regulated with the psp operon and is a member of the phage shock protein F regulon, we propose that yjbO be renamed pspG.
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PMID:Identification of a new member of the phage shock protein response in Escherichia coli, the phage shock protein G (PspG). 1548 10

We used gene sequencing to determine whether clinical (sporadic, epidemic, and endemic) and environmental isolates of Legionella pneumophila serogroup (sg) 1 belong to specific lineages. A total of 178 clinical and environmental L. pneumophila sg 1 isolates, defined by pulsed-field gel electrophoresis and epidemiological data as sporadic, epidemic, or endemic, were analyzed for polymorphisms in five gene fragments. The fragments belonged to three housekeeping genes (coding for aconitase [acn], aspartate-beta-semialdehyde dehydrogenase [asd], and RNA polymerase beta subunit [rpoB]) and two surface protein genes (coding for the macrophage infectivity potentiator [mip] and the major outer membrane protein [mompS]). The phylogenetic tree inferred from sequence polymorphisms of the five genes identified two large clusters, one consisting of 133 poorly differentiated strains and containing two smaller clusters (10 and 2 strains) unrelated to each other and the other consisting of 42 strains. Clinical and environmental isolates could not be distinguished on this basis, and no link between genetic background and epidemiological type was found, suggesting that other factors are responsible for differences in pathogenicity.
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PMID:Clinical and environmental isolates of Legionella pneumophila serogroup 1 cannot be distinguished by sequence analysis of two surface protein genes and three housekeeping genes. 1564 Jan 99

Escherichia coli has two osmo-responsive two-component regulatory systems, the EnvZ-OmpR and KdpD-KdpE systems, each of which consists of a sensor histidine protein kinase and a response regulator. The OmpR and KdpE response regulators belong to the same family of DNA-binding proteins, and act as positive transcriptional factors in response to the medium osmolarity. However, OmpR specifically activates the ompC gene encoding the OmpC outer membrane protein, whereas KdpE exclusively activates the kdpABC operon encoding the high-affinity Kdp potassium-transporter. To gain insight into the molecular basis for such strict promoter selectivity, we isolated OmpR mutants that can activate the non-cognate kdpABC promoter in vivo. For these OmpR mutants, it was found that a few common and crucial amino acids are responsible for the altered property of OmpR (e.g., Gly-164, Glu-193). In vitro properties of these OmpR mutants were further examined by means of DNA-binding assays and DNA-footprinting analyses with reference to the kdpABC promoter. These results were interpreted on the basis of the three-dimensional structure of the C-terminal half of OmpR, which consists of a DNA-binding helix-turn-helix motif and a RNA polymerase-interacting surface. The results of this study were best explained by assuming that the isolated OmpR mutants have an altered property with regard to the interaction with RNA polymerase on the kdpABC promoter. We propose that the promoter selectivity of OmpR is determined not only by its DNA-binding specificity, but also by the spatial configuration of the promoter on which OmpR must properly associate with RNA polymerase.
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PMID:Molecular basis for promoter selectivity of the transcriptional activator OmpR of Escherichia coli: isolation of mutants that can activate the non-cognate kdpABC promoter. 1571 83

The Large(myd) mouse has a loss-of-function mutation in the putative glycosyltransferase gene Large. Mutations in the human homolog (LARGE) have been described in a form of congenital muscular dystrophy (MDC1D). Other genes (POMT1, POMGnT1, fukutin, and FKRP) that encode known or putative glycosylation enzymes are also causally associated with human congenital muscular dystrophies. All these diseases are associated with hypoglycosylation of the membrane protein alpha-dystroglycan (alpha-DG) and consequent loss of extracellular ligand binding. Hence, they are termed dystroglycanopathies. A paralogous gene for LARGE (LARGE2 or GYLTL1B) may also have a role in DG glycosylation. Using database interrogation and reverse-transcriptase polymerase chain reaction (RT-PCR), we identified vertebrate orthologs of each of these LARGE genes in many vertebrates, including human, mouse, dog, chicken, zebrafish, and pufferfish. However, within invertebrate genomes, we were able to identify only single homologs. We suggest that vertebrate LARGE orthologs be referred to as LARGE1. RT-PCR, dot-blot, and northern analysis indicated that LARGE2 has a more restricted tissue-expression profile than LARGE1. Using epitope-tagged proteins, we show that both LARGE1 and LARGE2 localize to the Golgi apparatus. The high similarity between the LARGE paralogs suggests that LARGE2 may also act on DG. Overexpression of LARGE2 in mouse C2C12 myoblasts results in increased glycosylation of alpha-DG accompanied by an increase in laminin binding. Thus, there may be functional redundancy between LARGE1 and LARGE2. Consistent with this idea, we show that alpha-DG is still fully glycosylated in kidney (a tissue that expresses a high level of LARGE2 mRNA) of Large(myd) mutant mice.
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PMID:Characterization of the LARGE family of putative glycosyltransferases associated with dystroglycanopathies. 1595 17

One of the major limitations for understanding the biology of human mesenchymal stem cells (hMSCs) is the absence of prospective markers needed for distinguishing them from other cells and for monitoring lineage-specific differentiation. Mass spectrometry (MS)-based proteomics has proven extremely useful for analyzing complex protein expression patterns and, when applied quantitatively, can be used to resolve subtle differences between samples. Thus, we used MS to characterize changes in expression of membrane protein markers before and after short-term induction of osteoblast (OB) differentiation in a cell model of hMSCs established by overexpression of human telomerase reverse-transcriptase gene. We identified 463 unique proteins with extremely high confidence, including all known markers of hMSCs (e.g., SH3 [CD71], SH2 [CD105], CD166, CD44, Thy1, CD29, and HOP26 [CD63]) among 148 integral membrane or membrane-anchored proteins and 159 membrane-associated proteins. Twenty-nine integrins and cell adhesion molecules, 20 receptors, and 18 Ras-related small GTPases were also identified. Upon OB differentiation, the expression levels of 83 proteins increased by at least twofold whereas the levels of another 21 decreased by at least twofold. For example, alkaline phosphatase (ALP), versican core protein, and tenascin increased 27-, 12-, and 4-fold, respectively, and fatty acid synthase decreased sixfold. The observed increases in veriscan and ALP were confirmed using immunocytochemistry and cytochemistry. Quantitative real-time reverse transcription-polymerase chain reaction confirmed the presence of mRNA of these membrane proteins. However, with the exception of ALP, no concordance was detected between the changes in levels of gene and protein expression during OB differentiation. In conclusion, MS-based proteomics can reveal novel markers for MSCs that can be used for their isolation and for monitoring OB differentiation.
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PMID:Differential expression profiling of membrane proteins by quantitative proteomics in a human mesenchymal stem cell line undergoing osteoblast differentiation. 1621 Apr 10

Rickettsia felis is maintained transovarially in Ctenocephalides felis fleas in a widespread geographic distribution and is transmitted to humans and animals, including opossums. This rickettsia is phylogenetically a member of the spotted fever group, most closely related to Rickettsia akari and R. australis. An unusual feature of this rickettsia is that the gene for the outer membrane protein A (OmpA) is interrupted by stop codons. To determine if this putatively dying gene is expressed, mRNA was extracted from laboratory-maintained, R. felis-infected cat fleas. Reverse transcriptase-polymerase chain reaction amplification of three segments of the ompA gene indicated that mRNA of ompA is actively transcribed in fleas. The cDNA sequences expressed represented mRNA of the first 1860-basepair segment of ompA, which includes domains I and II, part of domain III, the region from site 1836 to site 2180, despite the presence of several stop codons, and the open reading frame from site 2788 to site 3837. The detected sequences showed several differences in the amino acid composition when compared with the previously reported sequence.
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PMID:Transcription of the Rickettsia felis ompA gene in naturally infected fleas. 1622 5

Studies of the ferric citrate transport genes in Escherichia coli K-12 have revealed a novel type of transcriptional regulation. The inducer, ferric citrate, binds to an outer membrane protein and must not be transported into the cells to initiate transcription of the ferric citrate transport genes. Rather, a signaling cascade from the cell surface across the outer membrane, the periplasm, and the cytoplasmic membrane into the cytoplasm transmits information on the presence of the inducer in the culture medium into the cytoplasm, where gene transcription occurs. The outer membrane protein FecA serves as a signal receiver and as a signal transmitter across the outer membrane. The FecR protein serves as a signal receiver in the periplasm and as a signal transmitter across the cytoplasmic membrane into the cytoplasm, where the FecI sigma factor is activated to bind RNA polymerase and specifically initiate transcription of the fecABCDE transport genes by binding to the promoter upstream of the fecA gene. Transcription of the fecI fecR regulatory genes is repressed by Fe(2+) bound to the Fur repressor protein. Under iron-limiting conditions, Fur is not loaded with Fe(2+), the fecI and fecR genes are transcribed, and the FecI and FecR proteins are synthesized and respond to the presence of ferric citrate in the medium when ferric citrate binds to the FecA protein. Regulation of the fec genes represents the paradigm of a growing number of gene regulation systems involving transmembrane signaling across three cellular compartments.
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PMID:Gene regulation by transmembrane signaling. 1633 51


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