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)

Nucleic acid biosynthesis was studied in rat embryo cell (REC) cultures 48 hours after infection with X14 or H-1 parvovirus. The incorporation of 14C-formate and [6-(14C]-orotic acid into purines and pyrimidines of various was lowered after infection with these parvoviruses. 14C-Formate incorporation into acid-soluble thymine was greatly inhibited in H-1 virus-infected cells whereas it was slightly inhibited in X14 virus-infected cells. These results suggest that X14 virus-infected cells can carry out the biosynthesis of thymidylic acid utilizing some endogenous pyrimidine nucleotide (e.g. deoxycytidylic acid, via deoxyuridylic acid). In the infected cells, the nucleoplasmic RNA polymerase activity was strongly inhibited. This results suggests an interference by the two viruses with hosts RNA synthesis.
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PMID:Nucleic acid biosynthesis in rat embryo cells infected with X14 or H-1 parvovirus. 1 18

Transcription of the genome of the nondefective parvovirus BPV was examined in nuclei isolated from synchronized bovine fetal spleen cells. The relative levels of total RNA polymerase and RNA polymerase I, II, and III activities in nuclei isolated from BPV-infected and mock-infected cells were found to be similar throughout the course of infection. Hybridization of RNA synthesized in isolated nuceli indicated that BPV-specific RNA synthesis began during the period of 8 to 12 h postinfection and proceeded linearly until at least 20 h postinfection. By 20 h postinfection, 5% of the total RNA synthesized in nuclei from infected cells was virus specific. BPV-specific RNA synthesis was inhibited by 95% in the presence of 0.1 microgram of alpha-amanitin per ml, suggesting that the viral genome is transcribed by cellular RNA polymerase II.
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PMID:Transcription of the bovine parvovirus genome in isolated nuclei. 48 Apr 72

Adeno-associated virus (AAV) is a nonpathogenic parvovirus which normally requires helper adenovirus or herpes-virus for replication. We examined the growth of AAV type 2 in human lymphocytes and its possible interaction with HIV-1. Three B cell lines (CK-B, HS-2, and UC729) and four T cell lines (Molt-4, Jurkat, HUT78, and HUT78+HIV, which is persistently infected with HIV-1) were infected with AAV either in the presence or in the absence of adenovirus. AAV DNA was found in cells of all the lines following incubation with the virus, indicating absorption. AAV DNA replication occurred in most cell lines without particular preference for B or T cells, but only in the presence of helper virus, either adenovirus or Epstein-Barr virus. Expression of AAV proteins was examined by immunoblotting and ELISA, using sera specific for AAV Rep or capsid proteins. The level of AAV protein synthesis correlated with the efficiency of AAV DNA replication, and both varied between cell lines. The yield of infectious AAV was low in most cases, except in one T4 line (Jurkat), where AAV replication and protein synthesis in the presence of adenovirus were very extensive. In HUT78+HIV cells both adenovirus and AAV (in the presence of Ad2) replicated efficiently. The effects of adenovirus plus AAV coinfections on HIV-1 replication, measured by reverse-transcriptase (RT) activity, were mild. Infection with adenovirus or AAV alone resulted in a 60-70% increase in RT activity, while infection with AAV plus adenovirus resulted in a 20% decrease in RT activity. The yield of infectious AAV in this cell line was very low.
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PMID:Replication of adeno-associated virus type 2 in human lymphocytic cells and interaction with HIV-1. 137 38

The 5.2-kilobase (kb) genome of the autonomous parvovirus H-1 was transcribed in the rightward direction, yielding steady-state polyadenylated transcripts of 4.8, 3.2, and 2.9 kb. Detailed mapping of these transcripts demonstrated that the H-1 genome contained two overlapping transcription units: the larger unit extended from 4 map units (5' end) to 96 map units (3' end), and the smaller unit extended from 40 map units (5' end) to 96 map units (3' end). The 4.8- and 3.2-kb transcripts were derived from the larger transcription unit and differed by a 1,500-nucleotide segment (10 to 40 map units) which was present in the 4.8-kb transcript but was spliced from the 3.2-kb transcript. The 2.9-kb transcript, the most abundant of the three known H-1 transcripts, was derived from the smaller transcription unit. The sequence at each initiation site was consistent with the presence of a class II (RNA polymerase II) promoter, and cell-free transcription of parvovirus H-1 restriction fragments containing either promoter resulted in transcription of the correct DNA strand and produced 5' ends identical to those seen in vivo. All three transcripts contained a small but heterogeneous splice at 45 to 47 map units. Minor differences in splicing at this site may result in the synthesis of different viral proteins.
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PMID:Parvovirus H-1 expression: mapping of the abundant cytoplasmic transcripts and identification of promoter sites and overlapping transcription units. 300 44

The B19 parvovirus produces two capsid proteins in strikingly different quantities (VP1 less than 4%, VP2 greater than 96%) from overlapping RNAs that are derived from the same transcription unit. Immediately upstream from the VP1 translation initiation site is an unusual sequence containing multiple ATG triplets. During RNA processing this sequence is spliced out of VP2 RNA. To test the regulatory role on translation of this sequence containing upstream AUGs, synthetic RNAs were produced in vitro by T7 RNA polymerase from various plasmid constructions. Translation of VP1 RNA was very inefficient compared to VP2 RNA in a cell-free system, indicating that capsid protein production was regulated at the level of translation. Removal of upstream AUG sequences from VP1 RNA greatly increased the efficiency of translation. Conversely, the addition of the same AUG-rich sequence upstream of the initiation site of VP2 decreased its translation. These data indicate that an upstream AUG-rich region acts as a negative regulatory element in the translational control of B19 capsid protein production.
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PMID:Translational regulation of B19 parvovirus capsid protein production by multiple upstream AUG triplets. 339 47

Premature termination of transcription has been demonstrated by eukaryotic RNA polymerase II at specific sites in the major late transcriptional unit of SV40 and in one of the transcriptional units of the parvovirus, minute virus of mice (MVM) (Y. Aloni and N. Hay, CRC Critical Reviews of Biochem., 18:327-383, 1985). In both cases the prematurely terminated (attenuated) RNA can be folded into a hairpin structure followed by U-residues that resemble a termination signal in prokaryotes. The experiments presented herein demonstrate premature termination of transcription 185 nucleotides (nt) downstream from the major late promoter of adenovirus type 2 (Ad2) in vivo, and in vitro in isolated nuclei and in HeLa whole cell extract. As in SV40 and MVM the attenuated RNA of Ad2 can be folded into a hairpin structure followed by U-residues. Transcription-termination was significantly reduced when ITP replaced GTP and when Br-UTP replaced UTP in the transcription reaction mixture, indicating that RNA secondary structure and the rU-dA interactions, respectively, are parts of the termination signal. Moreover, in isolated nuclei transcription-termination at the attenuation site occurred when the reaction mixture contained between 50-150 mM NaCl but not when it contained 300 mM NaCl. These results indicate that, at least in isolated nuclei, attenuation can be regulated. The possible involvement of termination factor(s) in the regulation of attenuation is discussed.
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PMID:Human RNA polymerase II can prematurely terminate transcription of the adenovirus type 2 late transcription unit at a precise site that resembles a prokaryotic termination signal. 350 41

A 660 nucleotide adenovirus-associated virus type 2 (AAV2) DNA fragment which encodes the 5' terminal leader and the entire intervening sequence of the major viral mRNA has been cloned into pBR322, and its primary sequence has been determined. The 5' terminal viral mRNA sequence was deduced by sequencing the reverse-transcriptase cDNA extension product of a 5' end-labeled DNA primer complementary to the RNA 5' terminal region. From combined DNA and RNA sequence analyses (which confirm our previous mapping data) we conclude that the major AAV2 transcript contains a 5' terminal leader sequence about 55 nucleotides in length encoded from a continuous region of DNA (near position 39 on the viral genome) 320 bases from the RNA body. The DNA sequences of the splice junctions are similar to those found for other class II genes. No other nucleotide sequence, indicative of promotion at another (upstream) site, is present at the 5' terminus. The DNA region encoding and flanking the leader sequence displays structural features expected for a class II gene promoter, including the canonical ATATAA sequence 23-25 bases upstream from the presumed initiation site. When the cloned viral DNA fragment is transcribed in vitro by RNA polymerase II in a cell-free system, a transcript is produced with a 5' end that is similar or identical to that found on the in vivo mRNA. Taken together these data strongly suggest that the major polysomal RNA may be generated from a transcription unit with a promoter at position 39, even though this transcription unit is part of a larger transcription unit with an upstream promoter near position 6. This indication of overlapping transcription units with independent promoters provides a major new insight into parvovirus gene expression.
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PMID:Definition of a novel promoter for the major adenovirus-associated virus mRNA. 625 77

It has previously been reported that the region between nucleotides 259 and 383 immediately downstream from the P4 early promoter of parvovirus minute virus of mice, prototype strain (MVMp) is responsible for transcriptional attenuation. Attenuation results from the premature pausing of RNA polymerase II within this sequence (designated to as att) and seems to depend on potential RNA secondary structure. To assess the attenuation capacity of att under near physiological conditions, the early transcription unit of MVMp was replaced by the chloramphenicol acetyltransferase reporter gene under control of the early P4 promoter, in the presence or absence of att. The resulting recombinant vectors were encapsidated in parvovirus particles and replicated in cells after co-infection with the wild-type virus. The att fragment reduced the rate of expression of the reporter gene by approximately threefold, confirming previously reported data from transfection experiments performed in the same cellular system. This attenuation factor is unexpectedly high, considering that the 'readthrough' fold of the nascent viral transcript is thermodynamically more stable than the 'attenuation' configuration. In an attempt to elucidate this point, we sought for the presence of secondary structures in the template DNA molecule. In vitro nuclease probing of viral dsDNA revealed that the att fragment had a cruciform configuration with both complementary strands folding into the computer-predicted stem-loop 'attenuation' structure. These observations lead us to propose that the secondary structure of the DNA template may prompt the formation of the 'attenuation' stem-loop in nascent mRNAs by bringing corresponding self-complementary sequences into close proximity.
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PMID:Cruciform structure of a DNA motif of parvovirus minute virus of mice (prototype strain) involved in the attenuation of gene expression. 793 Nov 50

The adeno-associated virus type 2 (AAV) large Rep proteins can act to increase the ratio of spliced to unspliced AAV RNA when they are targeted to the transcription template via a Rep binding element. The required Rep binding site is both location and orientation independent; however, Rep enhancement decreases as the distance between the promoter and the intron of the affected transcription unit increases. Only the AAV intron and an extended polyadenylation site must remain for the AAV transcription unit to manifest responsiveness to Rep. A number of promoters, when driving the AAV capsid gene transcription unit, were responsive to targeted Rep, though to various degrees. Transactivation of transcription initiation is not sufficient for the enhancement of RNA processing, because activation of the P40 transcription unit by other activators targeted to this transcription template did not result in enhancement of the ratio of spliced to unspliced AAV RNA. These results suggest that Rep may act as a trans regulator of RNA processing by modulating such functions coupled to RNA polymerase II (RNA pol II) transcription, perhaps by affecting the composition of the transcription complex either prior to or during elongation. These results reveal another way in which gene expression can be regulated by trans-acting proteins and help explain an important feature of the parvovirus life cycle.
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PMID:The adeno-associated virus type 2 Rep protein regulates RNA processing via interaction with the transcription template. 1199 1

Parvovirus B19 has been proposed as the etiological agent of fulminant hepatitis (FH) or hepatitis-associated aplastic anemia (HAA). We studied the prevalence of parvovirus B19 in liver-tissue samples from patients with FH and HAA and from control subjects. In the first study, parvovirus B19 DNA was detected by nested polymerase chain reaction (PCR) in 4 of 15 livers from patients with FH and in 3 of 22 livers from patients with nonviral hepatic disease. In a second confirmatory study, livers were tested for parvovirus B19 and its variant erythroviruses, V9 and A6. Tissues were also tested by reverse-transcriptase PCR for the presence of parvovirus B19 transcripts as a marker of viral replication. There was no significant difference in the prevalence of parvovirus B19 DNA in livers from patients with FH or HAA, compared with liver-tissue samples from patients with hepatitis B virus (HBV) or hepatitis C virus (HCV) infection; parvovirus B19 transcripts were not detected. There was a significant increase (P<.1) in the prevalence of variant erythrovirus sequences in livers of patients with HBV or HCV hepatitis, the reason for which is currently unknown.
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PMID:Prevalence of parvovirus B19 in liver tissue: no association with fulminant hepatitis or hepatitis-associated aplastic anemia. 1272 38


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