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

---

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

Phosphonoacetate is a highly specific inhibitor of herpes simplex virus-induced DNA polymerase. Sensitivity of herpesvirus type 1 or type 2 induced DNA polymerase to the drug was similar. However, DNA polymerases from other sources such as the host cells (Wi-38), Micrococcus luteus, and hepatitis B virus were highly resistant. In addition, Escherichia coli RNA polymerase and reverse transcriptase of Rous sarcoma virus were also insensitive to the drug. Enzyme kinetic studies showed that inhibition was noncompetitive with respect to deoxyribonucleotide triphosphates. The Ki value was about 0.45 muM. The apparent Km values for dTTP, dATP, dCTP, and dGTP were 0.71, 0.75, 0.42, and 0.39 muM, respectively. The base composition of template has no profound effect on the extent of inhibition. The drug caused uncompetititve inhibition with respect to template which indicated that phosphonoacetate did not bind directly to template DNA. Results are presented which suggest that phosphonoacetate did not affect the formation of the enzyme-DNA complex but probably inhibited the elongation step of DNA polymerase reaction.
...
PMID:Mode of inhibition of herpes simplex virus DNA polymerase by phosphonoacetate. 5 71

Reverse transcriptase (RT) was first discovered as an essential catalyst in the biological cycle of retroviruses. However, in the past years evidence has accumulated showing that RTs are involved in a surprisingly large number of RNA-mediated transpositional events that include both viral and nonviral genetic entities. Although it is probable that some RT-bearing genetic elements like the different types of AIDS viruses and the mammalian LINE family have arisen in recent geological times, the possibility that reverse transcription first took place in the early Archean is supported by (1) the hypothesis that RNA preceded DNA as cellular genetic material; (2) the existence of homologous regions of the subunit tau of the E. coli DNA polymerase III with the simian immunodeficiency virus RT, the hepatitis B virus RT, and the beta' subunit of the E. coli RNA polymerase (McHenry et al. 1988); (3) the presence of several conserved motifs, including a 14-amino-acid segment that consists of an Asp-Asp pair flanked by hydrophobic amino acids, which are found in all RTs and in most cellular and viral RNA polymerases. However, whether extant RTs descend from the primitive polymerase involved in the RNA-to-DNA transition remains unproven. Substrate specificity of the AMV and HIV-1 RTs can be modified in the presence of Mn2+, a cation which allows them to add ribonucleotides to an oligo (dG) primer in a template-dependent reaction. This change in specificity is comparable to that observed under similar conditions in other nucleic acid polymerases. This experimentally induced change in RT substrate specificity may explain previous observations on the misincorporation of ribonucleotides by the Maloney murine sarcoma virus RT in the minus and plus DNA of this retrovirus (Chen and Temin 1980). Our results also suggest that HIV-infected macrophages and T-cell cells may contain mixed polynucleotides containing both ribo- and deoxyribonucleotides. The evolutionary significance of these changes in substrate specificities of nucleic acid polymerases is also discussed.
...
PMID:On the early emergence of reverse transcription: theoretical basis and experimental evidence. 128 61

The hepatitis B virus X gene encodes a transcription activator which stimulates the synthesis of RNAs from a variety of class II and III promoter elements. In this report, we present a mutational analysis which genetically demonstrates that the X gene actually encodes two, and possibly three, related polypeptides from a single mRNA using alternate translation initiation from any of three in-frame AUG codons. Genetic analysis shows that translation initiates at the 5' proximal AUG of X mRNA and produces a full-length 17-kDa X protein but in addition also likely initiates at either of two conserved, in-frame AUG codons, producing two amino-terminally truncated X proteins presumably of 8 and 6.6 kDa. Expression of mRNAs capable of encoding only one of each X protein all individually transactivate class III (RNA polymerase III)-transcribed promoters. However, class II (RNA polymerase II)-transcribed promoters displayed various requirements for the different X proteins. Expression of two X proteins, the 17- and 6.6-kDa species, was required to activate transcription of the simian virus 40 enhancer/early promoter. In contrast, activation of an NF-kappa B-dependent promoter was carried out only by mRNAs encoding the full-length 17-kDa X protein. These results indicate that the X gene encodes several related proteins that possess different transcriptional regulatory activities.
...
PMID:Alternate translation initiation on hepatitis B virus X mRNA produces multiple polypeptides that differentially transactivate class II and III promoters. 131 8

In vitro transcription of hepatitis B virus DNA (HBV DNA) was studied using nuclear extracts of human hepatoma cell lines. RNA polymerase II-dependent run-off transcription of pre-S mRNA under the control of pre-S1 promoter was observed in nuclear extracts obtained from HepG2 and PLC/PRF/5 cells, and the efficiencies in these extracts were significantly higher than those in nuclear extracts of non-liver cells such as HeLa, Molt-4, and Ehrlich. Analysis of run-off transcripts by the pre-S1 promoter, using deletion mutants of HBV DNA as templates and synthetic oligonucleotides as competitors, showed that hepatocyte nuclear factor 1 was necessary for initiation of in vitro transcription of pre-S mRNA. The run-off transcript of pregenome RNA was also detected and its initiation site was determined. Nuclear extracts of not only hepatoma cells but non-liver cells were active in transcription of pregenome RNA in vitro. However, run-off transcripts of S mRNA and X mRNA were not observed in this system. These results suggest that there were some differences between the mechanisms of HBV DNA transcription in vitro and in vivo. This in vitro transcription system will be useful for clarifying the mechanism regulating transcription of HBV DNA since the biochemical and functional characteristics of the nuclear factors can readily be analyzed.
...
PMID:In vitro transcription of the hepatitis B virus gene by nuclear extracts of human hepatoma cells. 185 Sep 18

In the hepatitis B virus (HBV) genome four long open reading frames (ORFs) have been found that encode the virus core, surface and polymerase proteins as well as a protein that appears to be involved in virus gene expression (X). However, all HBV genomes examined contain two addition ORFs designated ORF5 and ORF6. ORF5 is located on the same strand as the four known viral genes and is 70-100 codons in size. ORF6 is located on the DNA strand complementary to the one that encodes the other virus genes, and is approximately 210 codons in length. Both ORFs are located in the X gene region which corresponds to the 3' terminus of the linear RNA genome. Northern blot analysis identified an X region specific transcript of approximately 0.7 kb. Although this transcript may be the template for the translation of the X gene protein it may also be involved in the expression of the protein encoded by ORF5. The promoter for this transcript may consist, in part, of the 15 residue sequence GCYTGYYTTGCYCGC because this sequence is near the 5' end of the transcript, it is highly conserved among hepadnaviruses, and it contains sequences involved in RNA polymerase binding. Also, the nucleotides within this region of the hepadnavirus genome are capable of forming a stable (G = -18 kcal/mole) hairpin structure. Understanding the organization and gene expression of the X region may be crucial in expanding our knowledge on the biology of HBV.
...
PMID:Organization of the X gene region of the hepatitis B virus genome. 222 61

The transcriptional regulatory activity of the human hepatitis B virus (HBV) X-gene product was investigated. We demonstrate a new property for the HBV X-gene, the strong transcriptional trans-activation of promoters for class III genes. The stimulation of RNA polymerase III (pol III) as well as pol II promoters is shown in cells transiently transfected with the X-gene, and after its stable integration into hepatocytes. We demonstrate that X-gene containing cells stimulate the frequency of pol III transcription initiation by 20- to 40-fold, and accelerate the rate of formation of stable pol III initiation complexes in a manner indistinguishable from that of adenovirus E1a protein. Since the transcription factor TFIIIC has been shown to be limiting in the formation of stable pol III initiation complexes, template commitment experiments were performed which titrate the level of this factor in extracts. We show that X-protein containing extracts are far more efficient in forming stable pol III preinitiation complexes that cannot be competed away upon addition of a second template, indicating that TFIIIC is very probably a target of the X-protein. Thus, the HBV X-protein is apparently a member of a family of trans-activators capable of stimulating both pol II and III promoters, which includes the adenovirus E1a-protein and SV40 t antigen.
...
PMID:The hepatitis B virus X-gene product trans-activates both RNA polymerase II and III promoters. 230 39

Eight eukaryotic promoters have been tested for their activity in vivo in Escherichia coli. The rat beta-actin, rat amylase, rat chymotrypsin B, mouse metallothionein I, rat insulin I, human insulin, Rous sarcoma virus long terminal repeat (RSV LTR) and hepatitis B viral precore promoter activities were measured by using the bacterial chloramphenicol acetyltransferase coding sequences as the reporter function and by primer extension RNA analysis. All eight promoter-chloramphenicol acetyltransferase constructs produce chloramphenicol acetyltransferase activity with the following relative strengths: RSV LTR greater than rat beta-actin greater than rat insulin I greater than rat amylase greater than hepatitis B virus precore greater than human insulin greater than rat chymotrypsin B greater than mouse metallothionein I. A primer extension analysis indicates that transcription from the RSV LTR, rat insulin I, and rat beta-actin promoters initiates at the sites expected for eukaryotic rather than prokaryotic promoters. Thus the site of initiation is determined by the DNA sequence rather than by the RNA polymerase.
...
PMID:Eukaryotic promoters drive gene expression in Escherichia coli. 268 Nov 82

A novel expression system based on coinfection of cells with two recombinant vaccinia viruses has been developed. One recombinant vaccinia virus contained the bacteriophage T7 RNA polymerase gene under control of a vaccinia virus promoter. The second recombinant vaccinia virus contained a target gene of choice flanked by bacteriophage T7 promoter and termination sequences. Maximum expression of the target gene occurred when cells were infected with 10 PFU of each recombinant virus. Although T7 RNA polymerase synthesis began shortly after infection, the target gene was not expressed until late times and was largely inhibited when DNA replication was blocked. Target gene transcripts were analyzed by agarose gel electrophoresis and had the predicted size. With this system, Escherichia coli beta-galactosidase, hepatitis B virus surface antigen, and human immunodeficiency virus envelope proteins were made. In each case, the level of synthesis was greater than had previously been obtained with the more conventional recombinant vaccinia virus expression system.
...
PMID:Use of a hybrid vaccinia virus-T7 RNA polymerase system for expression of target genes. 311 59

DNA fragments preceding open reading frames in a conserved segment of the vaccinia virus genome (Plucienniczak A., et al. (1985) Nucleic Acids Res. 13, 985-998) were cloned into plasmids upstream of the S gene of the hepatitis B virus encoding the surface antigen (HBsAg). Recombinant vaccinia virus obtained after insertion of these constructs into the thymidine kinase gene were used to infect mouse 1D cells. HBsAg was assayed in cellular supernatants. A strong promoter was thus identified in a 295 bp fragment preceding the coding region of the 147 kDa subunit of the vaccinia RNA polymerase.
...
PMID:Identification of vaccinia promoters by heterologous expression of hepatitis B surface antigen in mouse cells infected by recombinant vaccinia viruses. 367 23

We employed an in vitro cell-free transcription system to locate RNA polymerase II promoters on the hepatitis B virus genome. The strongest promoter precedes the surface antigen (HBsAg) gene, which is comprised of a long (500 base pairs) presurface region as well as the mature HBsAg coding sequence. The origin of this transcript was localized by using truncated templates and S1 endonuclease mapping. The activity of the promoter was confirmed in transfection experiments in which the complete HBsAg gene was introduced into monkey kidney cells via a simian virus 40 expression vector. A second RNA polymerase II promoter preceding the HBcAg gene was also active in the cell-free system. The presence of multiple promoters in the hepatitis B virus genome suggests that the relative levels of viral-specific proteins detected in liver and serum may reflect differential or regulated promoter efficiency.
...
PMID:Transcription of hepatitis B virus by RNA polymerase II. 664 22


1 2 3 4 5 6 7 8 9 10 Next >>

---