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)

While growing in the tsetse fly, Trypanosoma brucei expresses a major surface glycoprotein, the procyclic acidic repetitive protein (PARP). The parp genes are transcribed by an alpha-amanitin-resistant RNA polymerase. We have determined the sequence requirements for parp promoter activity. Studies of RNA produced from input DNA in transiently transfected trypanosomes indicate that the RNA is correctly processed by trans-splicing and polyadenylation. Deletion analyses show that 330 bp are sufficient for full promoter and splicing activity and that the promoter structure is complex, involving at least three elements whose mutual spacing is important. Mutagenesis pin-pointed two sequences vital for promoter activity; neither bears any resemblance to known prokaryotic or eukaryotic promoter elements.
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PMID:Anatomy of the parp gene promoter of Trypanosoma brucei. 184 May 21

An alternative approach to structure-function analysis of vesicular stomatitis virus (VSV) gene products and their interactions with one another during each phase of the viral life cycle is described. We showed previously by using the vaccinia virus-T7 RNA polymerase expression system that when cells expressing the nucleocapsid protein (N), the phosphoprotein (NS), and the large polymerase protein (L) of VSV were superinfected with defective interfering (DI) particles, rapid and efficient replication and amplification of (DI) particle RNA occurred. Here, we demonstrate that all five VSV proteins can be expressed simultaneously when cells are contransfected with plasmids containing the matrix protein (M) gene and the glycoprotein (G) gene of VSV in addition to plasmids containing the genes for the N, NS, and L proteins. When cells coexpressing all five VSV proteins were superinfected with DI particles, which because of their defectiveness are unable to express any viral proteins or to replicate, DI particle replication, assembly, and budding were observed and infectious DI particles were released into the culture fluids. Omission of either the M or G protein expression resulted in no DI particle budding. The vector-supported DI particles were similar in size and morphology to the authentic DI particles generated from cells coinfected with DI particles and helper VSV and their infectivity could be blocked by anti-VSV or anti-G antiserum. The successful replication, assembly, and budding of DI particles from cells expressing all five VSV proteins from cloned cDNAs provide a powerful approach for detailed structure-function analysis of the VSV gene products in each step of the replicative cycle of the virus.
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PMID:Cells that express all five proteins of vesicular stomatitis virus from cloned cDNAs support replication, assembly, and budding of defective interfering particles. 184 19

Patients undergoing penetrating keratoplasty for prior herpes simplex keratitis (group A) and corneal disease unrelated to herpes simplex (group B) were investigated to assess whether the cornea is a site for herpes simplex viral latency. All patients were seropositive for herpes simplex viral antibody. Virus was isolated from the tear film postoperatively in one patient and on cocultivation from the cornea of another patient. Herpes simplex viral DNA, however, was detected in the corneas of all patients from group A and half of those from group B by means of the polymerase chain reaction and primers to three well separated regions of the viral genome. Three donor corneas had no evidence of herpes simplex viral DNA. Using RNA polymerase chain reaction, we found evidence of a latency associated transcript and also that of a glycoprotein C coding transcript in two corneas, indicating viral replication. Nine corneas had evidence of a latency associated transcript but no glycoprotein C transcript, which suggests that herpes simplex virus may be maintained in a latent state in the corneas of patients with prior herpes simplex keratitis and in some patients with corneal disease unrelated to the herpes simplex virus.
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PMID:Evidence for herpes simplex viral latency in the human cornea. 185 Jun 15

The major surface antigens of Trypanosoma brucei are the VSG (variant surface glycoprotein) at the bloodstream stage, and procyclin at the procyclic stage. Variation in the VSG allows the parasite to escape the antibody response of its mammalian host. This occurs through either DNA rearrangement in the telomeric VSG gene expression site, or alternate activation, without DNA rearrangement, of different telomeric expression sites. The VSG and procyclin genes each belong to large, polycistronic transcription units. Although the promoters of these units are both active at the two main stages of the parasite life cycle, stage-specific controls operating at the level of RNA elongation and processing lead to strictly differential expression of the end products of the two units. Despite their mutually exclusive control of expression, the VSG and procyclin transcription units share common characteristics. Both contain a similar gene, and both are transcribed by the same type of RNA polymerase, unusually resistant to alpha-amanitin. Among the eight genes present in the VSG transcription unit, two may be involved in the synthesis of cyclic AMP. The function of the other genes is unknown.
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PMID:Genetics of antigenic variation in African trypanosomes. 196 83

The expression site for the variant surface glycoprotein (VSG) gene of Trypanosoma brucei contains several genes of unknown function (ESAGs, for expression site-associated genes). Among these, ESAG 4 shows homology to eukaryotic adenylate/guanylate cyclase genes, in the region encoding the presumptive enzyme catalytic domain. This gene belongs to a family of related sequences, and hybridizes to the genomic DNA of other trypanosomatids, such as Trypanosoma congolense, Trypanosoma vivax and Trypanosoma mega. While ESAG 4 is transcribed only in bloodstream forms by a RNA polymerase resistant to alpha-amanitin, at least three other members of this family are transcribed in both bloodstream and procyclic forms, by a RNA polymerase sensitive to the drug. These genes encode different putative transmembrane proteins showing high sequence conservation in the region corresponding to the adenylate/guanylate cyclase catalytic domain.
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PMID:Differential expression of a family of putative adenylate/guanylate cyclase genes in Trypanosoma brucei. 198 55

The infection and coding strategies of three groups of negative-stranded RNA viruses (arena viruses, phleboviruses, and nairoviruses) that include the etiologic agents of hemorrhagic disease in humans have been studied. Arenaviruses have two viral RNA species. The smaller RNA species (S) codes for the viral nucleoprotein (N protein) and for the viral glycoprotein species (G1 and G2, which are derived from a precursor glycoprotein, GPC). The S RNA has an ambisense arrangement. The proteins are translated from subgenomic mRNA species (viz., N protein from a viral-complementary mRNA and glycoprotein from a viral-sense mRNA). The larger arenavirus RNA species (L) is presumed to code for the viral transcriptase/replicase. Phleboviruses and nairoviruses are members of the Bunyaviridae. They both have three species of viral RNA. Other than the sizes of the viral proteins and the viral RNA species, virtually nothing is known about the coding strategy of nairoviruses. Phleboviruses have an ambisense coding arrangement to their smallest (S) RNA species. This S RNA codes for the viral N protein (translated from a viral-complementary mRNA) and a nonstructural protein (translated from a viral-sense mRNA). The middle-size (M) RNA of phleboviruses codes for a precursor to the viral glycoproteins (translated from a viral-complementary mRNA). The largest viral RNA (L) is presumed to code for the viral transcriptase/replicase.
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PMID:Infection and coding strategies of arenaviruses, phleboviruses, and nairoviruses. 254 46

Polypeptides have been defined by studying structural and nonstructural proteins. The rotavirus outer capsid is made up of three proteins: VP7, VP3 and VP9. VP7 is a glycoprotein involved in cell attachment and viral maturation. VP3 is associated with hemagglutination and trypsin activation of virus infectivity; both contain type-specific neutralization determinants. A biological function has not yet been completely defined for VP9. VP6, the main protein of the inner capsid is necessary for mRNA synthesis by the viral transcriptase and determines the subgroup antigenic specificity. These two capsids surround the core which consists of three proteins VP1, VP2, and the product of segment 3, associated with RNA polymerase. Four non-structural polypeptides have been identified (NCVP5, NCVP4, NCVP2, NCVP3); very little is known about their biological role.
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PMID:[Rotaviruses: structure and function of the principal polypeptides]. 255 46

The simian rotavirus SA11 genome segment 10 codes for a nonstructural glycoprotein, NS28, that has been hypothesized to be involved in budding of viral particles into the endoplasmic reticulum (ER) membrane. Previous studies had suggested that NS28 is an integral membrane protein of the ER, possibly a transmembrane protein. We have examined the topography of NS28 inserted in microsomal membranes following cell-free translation of genome segment 10 transcripts. These transcripts were obtained either by hybrid selection of mRNA synthesized by the endogenous viral RNA polymerase or by in vitro transcription of genome segment 10 cDNA using SP6 polymerase. Full-length and truncated gene 10 transcripts were translated in a cell-free system supplemented with dog pancreatic microsomes. The existence of a cytoplasmic domain of the translation product was demonstrated by protease protection experiments. An 18,000 (18K) mol wt glycosylated polypeptide was protected from digestion with proteinase K and trypsin, whereas chymotrypsin digestion yielded a 23K mol wt glycosylated polypeptide. Correlation of these biochemical data with the known sequence of NS28 suggests that a 10K mol wt hydrophilic, carboxy-terminal fragment (from amino acid number 86 to amino acid number 175) of this glycoprotein is exposed on the cytoplasmic side of the ER membrane. A model of how NS28 folds in the ER membrane is proposed.
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PMID:Topography of the simian rotavirus nonstructural glycoprotein (NS28) in the endoplasmic reticulum membrane. 283 61

The synthesis of viral proteins and S RNAs in cells infected with 12 temperature-sensitive (ts) mutants of Pichinde virus was characterized. The mutants could be divided into five groups on the basis of the patterns of radiolabeled proteins immunoprecipitated from infected-cell lysates. Markedly reduced nucleoprotein levels and undetectable amounts of glycoprotein precursor and L protein were synthesized at the nonpermissive temperature in cells infected with five of the mutants. Reduced but detectable amounts of the viral proteins were synthesized at the nonpermissive temperature in cells infected with a single mutant. Two mutants were associated with the intracellular accumulation of glycoprotein precursor, which was apparently not transported across the cell membrane in cells incubated at the nonpermissive temperature. The synthesis of viral proteins in cells infected with two mutants was indistinguishable from those produced by wild-type virus. Two additional mutants were associated with markedly reduced amounts of immunoprecipitable proteins in infected cells incubated at both the permissive and nonpermissive temperatures. Analysis of viral RNA with radiolabeled single-stranded cDNA probes representing complementary and genomic-sense sequences corresponding to the 3' region of S RNA revealed two basic patterns of viral RNA synthesis. At the nonpermissive temperature, the synthesis of complementary- and genomic-sense sequences and mRNA of the S RNA segment was markedly reduced in cells infected with representative members of these mutant groups, suggesting the presence of mutations altering transcriptase activity. Viral-complementary- and genomic-sense sequence and RNA synthesis, as well as nucleoprotein mRNA in cells, was detected in reduced amounts for mutants associated with reduced levels of proteins at both temperatures. Interestingly, RNA species larger than the S RNA segment were detected in cells infected with some of the mutants, especially those with putative transcriptase lesions. These molecules suggest a possible oligomeric intermediate in the synthesis of S RNA of Pichinde virus.
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PMID:Characterization of temperature-sensitive mutants of Pichinde virus. 317 36

A procedure has been developed for the sequential removal and purification of the glycoprotein and membrane protein of vesicular stomatitis virus (VSV). Neither of these proteins exhibited transcriptase activity. All of the activity was recovered in the ribonucleic acid (RNA)-ribonucleoprotein complex of VSV, which also has four other minor proteins associated with it. During transcription of 41% of the RNA of a virus preparation, no dissociation of the ribonucleoprotein from the viral RNA was observed.
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PMID:Dissociation of vesicular stomatitis virus and relation of the virion proteins to the viral transcriptase. 434 41


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