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)

The DNA-dependent protein kinase (DNA-PK) is involved in several fundamental nuclear processes, including DNA double-strand break repair, V(D)J recombination, and transcription by RNA polymerases I and II. In this study, we show that infection of mammalian cells with herpes simplex virus type 1 attenuates DNA-PK activity by specifically depleting the p350/DNA-PKcs catalytic subunit. The half-life of the p350/DNA-PKcs protein decreases from greater than 24 h to less than 4 h following infection. The depletion of DNA-PK activity and p350/DNA-PKcs abundance is dependent on expression of the viral immediate-early protein ICP0. As ICP0 acts as a promoter-independent transactivator of gene expression, these data suggest that ICP0 may function by directly or indirectly targeting the p350/DNA-PKcs subunit of DNA-PK, thereby altering the inhibitory effects of DNA-PK on RNA polymerase II transcription.
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PMID:Attenuation of DNA-dependent protein kinase activity and its catalytic subunit by the herpes simplex virus type 1 transactivator ICP0. 889 65

The ICP4 homolog of Marek's disease virus (MDV ICP4) is a possible candidate for the transactivator of the early genes. We transfected MDCC-MSB-1 (MSB-1) tumor cells with plasmid including a coding region of MDV ICP4 using cationic liposome. As carriers for intranuclear transport, high mobility group -1 and -2 proteins were bound to the plasmid DNA before forming liposomes. We detected transcripts from the plasmid 2 hr after transfection by quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) analysis. We also detected abundant transcripts of endogenous ICP4 2-96 hr after transfection. These data suggested that expression of introduced MDV ICP4 gene enhanced the expression of endogenous MDV ICP4. On the other hand, quantitative PCR analysis for virus genome DNA indicated no significant alteration of copy number of virus genome in transfected MSB-1 cells, suggesting that reactivation of virus requires more than turning on MDV ICP4 gene.
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PMID:Expression of the endogenous Marek's disease virus ICP4 homolog (MDV ICP4) gene is enhanced in latently infected cells by transient transfection with the recombinant MDV ICP4 gene. 890 Oct 28

The Myb family of transcription factors is defined by homology within the DNA binding domain and includes c-Myb, A-Myb, and B-Myb. The protein products of the myb genes all bind the Myb-binding site (MBS) [YG(A/G)C(A/C/G)GTT(G/A)]. A-myb has been found to display a limited pattern of expression. Here we report that bovine aortic smooth muscle cells (SMCs) express A-myb. Sequence analysis of isolated bovine A-myb cDNA clones spanning the entire coding region indicated extensive homology with the human gene, including the putative transactivation domain. Expression of A-myb was cell cycle dependent; levels of A-myb RNA increased in the late G1-to-S phase transition following serum stimulation of serum-deprived quiescent SMC cultures and peaked in S phase. Nuclear run-on analysis revealed that an increased rate of transcription can account for most of the increase in A-myb RNA levels. Treatment of SMC cultures with 5,6-dichlorobenzimidazole riboside, a selective inhibitor of RNA polymerase II, indicated an approximate 4-h half-life for A-myb mRNA during the S phase of the cell cycle. Expression of A-myb by SMCs was stimulated by basic fibroblast growth factor, in a cell density-dependent fashion. Cotransfection of a human A-myb expression vector activated a multimerized MBS element-driven reporter construct approximately 30-fold in SMCs. The activity of c-myb and c-myc promoters, which both contain multiple MBS elements, were similarly transactivated, approximately 30- and 50-fold, respectively, upon cotransfection with human A-myb. Lastly, A-myb RNA levels could be increased by a combination of phorbol ester plus insulin-like growth factor 1. To test the role of myb family members in progression through the cell cycle, we comicroinjected c-myc and myb expression vectors into serum-deprived quiescent SMCs. The combination of c-myc and either A-myb or c-myb but not B-myb synergistically led to entry into S phase, whereas microinjection of any vector alone had little effect on S phase entry. Thus, these results suggest that A-myb is a potent transactivator in bovine SMCs and that its expression induces progression into S phase of the cell cycle.
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PMID:A-myb is expressed in bovine vascular smooth muscle cells during the late G1-to-S phase transition and cooperates with c-myc to mediate progression to S phase. 911 13

The human immunodeficiency virus (HIV) encodes a transcriptional transactivator (Tat), which binds to an RNA hairpin called the transactivation response element (TAR) that is located downstream of the site of initiation of viral transcription. Tat stimulates the production of full-length viral transcripts by RNA polymerase II (pol II). In this study, we demonstrate that Tat coimmunoprecipitates with the pol II holoenzyme in cells and that it binds to the purified holoenzyme in vitro. Furthermore, Tat affinity chromatography purifies a holoenzyme from HeLa nuclear extracts which, upon addition of TBP and TFIIB, supports Tat transactivation in vitro, indicating that it contains all the cellular proteins required for the function of Tat. By demonstrating that Tat interacts with the holoenzyme in the absence of TAR, our data suggest a single-step assembly of Tat and the transcription complex on the long terminal repeat of HIV.
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PMID:The human immunodeficiency virus transactivator Tat interacts with the RNA polymerase II holoenzyme. 912 29

Nonsegmented negative strand RNA viruses package an RNA-dependent RNA polymerase composed of two subunits, a large protein L and a phosphoprotein P, for transcription and replication of their genome RNAs. The RNA polymerase activity resides within the L protein, while the P protein acts as a transcription factor or transactivator of the polymerase. Since P protein is heavily phosphorylated and phosphorylation is known to regulate function of many viral as well as cellular proteins, the role of phosphorylation of P protein in the gene expression of this group of RNA viruses has recently been investigated. Through expression in bacteria the P protein was produced in large quantity in the nonphosphorylated form and involvement of cellular kinase(s) in its phosphorylation was studied. Casein kinase II and/or protein kinase C have been shown to play a critical role in the activation of P protein in transcription. These findings have opened up a new avenue for studying an important regulatory step in virus gene expression that may lead to the development of an effective antiviral agent.
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PMID:Role of cellular kinases in the gene expression of nonsegmented negative strand RNA viruses. 922 28

HIV-1 infection causes B cell hyperactivation. Tat protein, a potent virus-encoded transactivator, has the potential to activate B cells based on its pleiotropic biological properties: (1) Tat regulates cellular gene expression; (2) Tat modulates growth of various cell types; and (3) Tat is released from infected T cells and acts on bystander uninfected cells in a paracrine fashion. To test a possible activating effect of Tat on B cells, we examined the effect of purified Tat on the expression of Fas, an activation marker, in B cells in primary culture. Flow cytometric analysis demonstrated that treatment of peripheral blood mononuclear cells with Tat, at concentrations in the range of extracellular Tat as determined in vivo, up-regulated Fas expression in B cells. Reverse transcriptase-PCR further demonstrated that Tat induced Fas expression in B cells at the mRNA level. These results indicate that exogenous Tat alone can activate B cells, suggesting that Tat may contribute to B cell hyperactivation during the early stage of HIV-1 infection and activation-induced B cell death mediated by Fas during the late stage of HIV-1 infection.
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PMID:Human immunodeficiency virus type 1 TAT protein activates B lymphocytes. 926 34

The human immunodeficiency virus encodes the transcriptional transactivator Tat, which binds to the transactivation response (TAR) RNA stem-loop in the viral long terminal repeat (LTR) and increases rates of elongation rather than initiation of transcription by RNA polymerase II (Pol II). In this study, we demonstrate that Tat binds directly to the cyclin-dependent kinase 7 (CDK7), which leads to productive interactions between Tat and the CDK-activating kinase (CAK) complex and between Tat and TFIIH. Tat activates the phosphorylation of the carboxy-terminal domain (CTD) of Pol II by CAK in vitro. The ability of CAK to phosphorylate the CTD can be inhibited specifically by a CDK7 pseudosubstrate peptide that also inhibits transcriptional activation by Tat in vitro and in vivo. We conclude that the phosphorylation of the CTD by CAK is essential for Tat transactivation. Our data identify a cellular protein that interacts with the activation domain of Tat, demonstrate that this interaction is critical for the function of Tat, and provide a mechanism by which Tat increases the processivity of Pol II.
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PMID:The HIV transactivator TAT binds to the CDK-activating kinase and activates the phosphorylation of the carboxy-terminal domain of RNA polymerase II. 933 27

Chilo iridescent virus (CIV), the type species of the genus Iridovirus within the family Iridoviridae, is highly pathogenic for larvae of important pest insects. The virions contain a single linear double-stranded DNA molecule (209 kbp) that is circularly permuted and terminally redundant. The nucleotide sequence of the viral genome between the genome coordinates 0.101 and 0.391 (60,170 bp) was determined by automated cycle sequencing. This particular region of the CIV genome contains 112 open reading frames (ORFs) with coding capacities for 50 to 1186 amino acids. The alignment of the deduced amino acid sequences with well-characterized proteins stored in protein databases led to the identification of several genes with significant homologies, such as the largest subunit of the DNA-dependent RNA polymerase, large subunit of the ribonucleoside-diphosphate reductase, endonuclease, protein-tyrosine phosphatase, helicase, global transactivator, two apoptosis inhibitor homologs, antibiotic peptide homolog, and others. The highest homologies were detected between putative viral gene products of CIV and the corresponding viral proteins of lymphocystis disease virus of fish (LCDV), which belongs to the genus Lymphocystivirus within the iridovirus family.
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PMID:The DNA sequence of Chilo iridescent virus between the genome coordinates 0.101 and 0.391; similarities in coding strategy between insect and vertebrate iridoviruses. 948 89

The HIV-1 Tat protein is an RNA-binding transcriptional transactivator. Recent findings suggest that Tat associates with a cellular kinase that phosphorylates the carboxyl-terminal domain of the largest subunit of RNA polymerase II. Here we review, in brief, the role of Tat-associated kinase in Tat-activated transcription. We discuss evidence that suggests involvement of TFIIH and/or P-TEFb.
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PMID:Tat, Tat-associated kinase, and transcription. 957 May 10

DRB is a classic inhibitor of transcription by RNA polymerase II (pol II). Although it has been demonstrated that DRB inhibits the elongation step of transcription, its mode of action has been elusive. DRB also markedly inhibits human immunodeficiency virus (HIV) transcription, by targeting the elongation which is enhanced by the HIV-encoded transactivator Tat. Two factors essential for DRB action have recently been identified. These factors, positive transcription elongation factor b (P-TEFb) and DRB sensitivity-inducing factor (DSIF), positively and negatively regulate pol II elongation, and are likely to be relevant to the function of Tat. In this review, we summarize the recent findings on these factors, and discuss a possible model for the molecular mechanism of DRB action.
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PMID:Interplay between positive and negative elongation factors: drawing a new view of DRB. 958 78


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