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)

Alternative pre-mRNA splicing is a major mechanism utilized by eukaryotic organisms to expand their protein-coding capacity. To examine the role of cell signaling in regulating alternative splicing, we analyzed the splicing of the Drosophila melanogaster TAF1 pre-mRNA. TAF1 encodes a subunit of TFIID, which is broadly required for RNA polymerase II transcription. We demonstrate that TAF1 alternative splicing generates four mRNAs, TAF1-1, TAF1-2, TAF1-3, and TAF1-4, of which TAF1-2 and TAF1-4 encode proteins that directly bind DNA through AT hooks. TAF1 alternative splicing was regulated in a tissue-specific manner and in response to DNA damage induced by ionizing radiation or camptothecin. Pharmacological inhibitors and RNA interference were used to demonstrate that ionizing-radiation-induced upregulation of TAF1-3 and TAF1-4 splicing in S2 cells was mediated by the ATM (ataxia-telangiectasia mutated) DNA damage response kinase and checkpoint kinase 2 (CHK2), a known ATM substrate. Similarly, camptothecin-induced upregulation of TAF1-3 and TAF1-4 splicing was mediated by ATR (ATM-RAD3 related) and CHK1. These findings suggest that inducible TAF1 alternative splicing is a mechanism to regulate transcription in response to developmental or DNA damage signals and provide the first evidence that the ATM/CHK2 and ATR/CHK1 signaling pathways control gene expression by regulating alternative splicing.
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PMID:ATM and ATR pathways signal alternative splicing of Drosophila TAF1 pre-mRNA in response to DNA damage. 1703 Jun 24

Che-1 is a RNA polymerase II-binding protein involved in the transcription of E2F target genes and induction of cell proliferation. Here we show that Che-1 contributes to DNA damage response and that its depletion sensitizes cells to anticancer agents. The checkpoint kinases ATM/ATR and Chk2 interact with Che-1 and promote its phosphorylation and accumulation in response to DNA damage. These Che-1 modifications induce a specific recruitment of Che-1 on the TP53 and p21 promoters. Interestingly, it has a profound effect on the basal expression of p53, which is preserved following DNA damage. Notably, Che-1 contributes to the maintenance of the G2/M checkpoint induced by DNA damage. These findings identify a mechanism by which checkpoint kinases regulate responses to DNA damage.
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PMID:Che-1 phosphorylation by ATM/ATR and Chk2 kinases activates p53 transcription and the G2/M checkpoint. 1715 88

Che-1 is a RNA polymerase II binding protein involved in the transcriptional regulation of E2F target-genes and in cell proliferation. Recently, it has been shown that Che-1 accumulates in cells responding to genotoxic agents, such as Doxorubicin and ionizing radiations. The DNA damage-activated checkpoint kinases ATM and Chk2 interact with and phosphorylate Che-1, enhancing its accumulation and stability, and promoting Che-1-mediated transcription of p53-responsive genes and of p53 itself, as evidenced by microarray analysis. This transcriptional response is suppressed by expression of a Che-1 mutant lacking ATM and Chk2 phosphorylation amino acid residues, or by depletion of Che-1 by RNA silencing. In addition, chromatin immunoprecipitation analysis has shown that Che-1 is released from the E2F-target genes and recruited to the p21 and p53 promoters after DNA damage. Lastly, Che-1 contributes to the maintenance of the G2/M checkpoint in response to genotoxic stresses. These findings identify a new mechanism by which the checkpoint kinases regulate, via the novel effector Che-1, the p53 pathway.
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PMID:Che-1: a new effector of checkpoints signaling. 1737 93

DNA lesions interfere with DNA and RNA polymerase activity. Cyclobutane pyrimidine dimers and photoproducts generated by ultraviolet irradiation cause stalling of RNA polymerase II, activation of transcription-coupled repair enzymes, and inhibition of RNA synthesis. During the S phase of the cell cycle, collision of replication forks with damaged DNA blocks ongoing DNA replication while also triggering a biochemical signal that suppresses the firing of distant origins of replication. Whether the transcription machinery is affected by the presence of DNA double-strand breaks remains a long-standing question. Here we monitor RNA polymerase I (Pol I) activity in mouse cells exposed to genotoxic stress and show that induction of DNA breaks leads to a transient repression in Pol I transcription. Surprisingly, we find Pol I inhibition is not itself the direct result of DNA damage but is mediated by ATM kinase activity and the repair factor proteins NBS1 (also known as NLRP2) and MDC1. Using live-cell imaging, laser micro-irradiation, and photobleaching technology we demonstrate that DNA lesions interfere with Pol I initiation complex assembly and lead to a premature displacement of elongating holoenzymes from ribosomal DNA. Our data reveal a novel ATM/NBS1/MDC1-dependent pathway that shuts down ribosomal gene transcription in response to chromosome breaks.
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PMID:The ATM repair pathway inhibits RNA polymerase I transcription in response to chromosome breaks. 1755 10

The mechanisms by which DNA-damaging agents trigger the induction of the stress response protein p53 are poorly understood but may involve alterations of chromatin structure or blockage of either transcription or replication. Here we show that transcription-blocking agents can induce phosphorylation of the Ser-15 site of p53 in a replication-independent manner. Furthermore, microinjection of anti-RNA polymerase II antibodies into the nuclei of cells showed that blockage of transcription is sufficient for p53 accumulation even in the absence of DNA damage. This induction of p53 occurs by two independent mechanisms. First, accumulation of p53 is linked to diminished nuclear export of mRNA; and second, inhibition specifically of elongating RNA polymerase II complexes results in the phosphorylation of the Ser-15 site of p53 in a replication protein A (RPA)- and ATM and Rad3-related (ATR)-dependent manner. We propose that this transcription-based stress response involving RPA, ATR, and p53 has evolved as a DNA damage-sensing mechanism to safeguard cells against DNA damage-induced mutagenesis.
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PMID:RPA and ATR link transcriptional stress to p53. 1768 92

Che-1 is a RNA polymerase II binding protein involved in the transcriptional regulation of E2F target genes and in cell proliferation. Recently, it has been shown that Che-1 accumulates in cells responding to genotoxic agents such as Doxorubicin and ionizing radiation. The DNA damage-activated checkpoint kinases ATM and Chk2 interact with and phosphorylate Che-1, enhancing its accumulation and stability, and promoting Che-1-mediated transcription of p53-responsive genes and of p53 itself, as evidenced by microarray analysis. This transcriptional response is suppressed by expression of a Che-1 mutant lacking ATM and Chk2 phosphorylation amino acid residues, or by depletion of Che-1 by RNA silencing. In addition, chromatin immunoprecipitation analysis has shown that Che-1 is released from E2F target genes and recruited to the p21 and p53 promoters after DNA damage. Che-1 contributes to the maintenance of the G2/M checkpoint in response to genotoxic stress. These findings identify a new mechanism by which the checkpoint kinases regulate, via the novel effector Che-1, the p53 pathway. Lastly, increasing evidence suggests that Che-1 may be involved in apoptotic signaling in neural tissues. In cortical neurons, Che-1 exhibits anti-apoptotic activity, protecting cells from neuronal damage induced by amyloid beta-peptide. In cerebellar granule neurons, Che-1 interacts with Tau in the cytoplasmic compartment and this interaction is modulated during neuronal apoptosis. Finally, Che-1 directly interacts with the neuronal cell-death inducer "NRAGE" which downregulates endogenous Che-1 by targeting it for proteasome-dependent degradation. These findings identify Che-1 as a novel cytoprotective factor against apoptotic insults and suggest that Che-1 may represent a potential target for therapeutic application.
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PMID:The anti-apoptotic factor Che-1/AATF links transcriptional regulation, cell cycle control, and DNA damage response. 1763 35

The DNA topoisomerase I (topo1) inhibitor topotecan (TPT) and topo2 inhibitors doxorubicin, etoposide and mitoxantrone (MXT) are widely used antitumor drugs. They stabilize otherwise transient ("cleavable") complexes of topo1 or topo2 with DNA, respectively. Collisions of DNA replication forks (during replication) or progressing RNA polymerase molecules (during transcription) with these complexes convert them into double-strand DNA breaks (DSBs). Formation of DSBs triggers activation of ATM and phosphorylation of histone H2AX, the markers that have been used to correlate DNA damage with cell cycle phase or induction of apoptosis. In the present study we explored a relationship between H2AX phosphorylation and activation of checkpoint kinase 2 (Chk2) in human lung carcinoma A549 cells treated with TPT or with MXT. Activation of Chk2 was detected immunocytochemically using a phospho-specific (Thr68) Ab and measuring Chk2-Thr68(P)immunofluorescence (IF), concurrently with DNA content, by laser scanning cytometry. In the untreated cells, activated Chk2 was present predominantly in centrosomes. Upon treatment with TPT or MTX, the activated Chk2 presented itself in form of either minute or large IF foci in the cell's nucleoplasm. H2AX phosphorylation whether induced by TPT or MXT was rapid, with the maximal rate occurring during the initial 2 h and peaking at 2 h of treatment. TPT or MXT induced Chk2 activation occurred at a distinctly slower pace, peaking at 4 h. While TPT-induced H2AX phosphorylation and Chk2 activation were maximal in S-phase cells, Chk2 activation was also much pronounced in G(2)M cells; the least affected by TPT were G(1) cells. MTX-induced H2AX phosphorylation was maximal in G(1) cells while Chk2 activation was maximal in G(2)M and minimal in G(1) cells. The pattern of cell-cycle phase specific response to TPT or MXT by H2AX phosphorylation and Chk2 activation was different when measured either as integrated or maximal pixel of gammaH2AX or Chk2-Thr68(P) IF, the former reflecting total IF per nucleus the latter stressing the punctate (foci) character of expression of these phospho-modified proteins.
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PMID:Kinetics of histone H2AX phosphorylation and Chk2 activation in A549 cells treated with topotecan and mitoxantrone in relation to the cell cycle phase. 1845 60

Cellular stress and DNA damage up-regulate and activate p53, fundamental for cell cycle control, senescence, DNA repair and apoptosis. The specific mechanism(s) that determine whether p53-dependent cell cycle arrest or p53-dependent apoptosis prevails in response to specific DNA damage are poorly understood. In this study, we investigated two types of DNA damage, chromium treatment and gamma irradiation (IR) that induced similar levels of p53, but that mediated two distinct p53-dependent cell fates. Chromium exposure induced a robust DNA-dependent protein kinase (DNA-PK)-mediated apoptotic response that was accompanied by the rapid loss of the cyclin-dependent kinase inhibitor 1A (p21) protein, whereas IR treatment-induced cell cycle arrests that was supported by the rapid induction of p21. Inhibition of DNA-PK effectively blocked chromium-, but not IR-induced p53 stabilization and activation. In contrast, inhibition of ATM and ATR by caffeine had the inverse effect of blocking IR-, but not chromium-induced p53 stabilization and activation. Chromium exposure ablated p21 transcription but PUMA and Bax transcription was significantly enhanced compared to non-damaged cells. In contrast, IR treatment triggered significant p21 mRNA synthesis in addition to PUMA and Bax mRNA production. While chromium treatment enhanced the binding of p53 and RNA polymerase II (RNA Pol II) to both the p21 and PUMA promoters, RNA Pol II elongation was only observed along the PUMA gene and not the p21 gene. In contrast, following IR treatment, RNA Pol II elongation was observed on both p21 and PUMA. Chromium-induced apoptosis therefore involves DNA-PK-mediated p53 activation followed by preferential transcription of pro-apoptotic PUMA over anti-apoptotic p21 genes.
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PMID:Chromium-mediated apoptosis: involvement of DNA-dependent protein kinase (DNA-PK) and differential induction of p53 target genes. 1860 74

This study was aimed at investigating the effects of Angiotensin (Ang) II stimulation on T lymphocytes mRNA expression of angiotensinogen (AGTN), angiotensin-converting enzyme (ACE) and AT1-receptor (R) and on ACE activity and Ang II content. The effects of Ang II stimulus were studied in lipopolysaccharide (LPS)-stimulated or not stimulated lymphocytes. mRNA expression for interferon-gamma (INF-gamma) was also studied to investigate whether a link between lymphocyte RAS and immunological function might occur. mRNAs for AGTN, ACE and AT1-R were obtained from peripheral blood of 18 healthy subjects and were quantified by real time quantitative transcriptase-polymerase chain reaction (PCR). ACE activity was assayed in cell pellets and supernatants by measuring the hippuric acid formation by high performance liquid chromatography (HPLC) and Ang II cell content was measured by radioimmunoassay (RIA) after HPLC separation. All determination were performed under baseline conditions and after the addition of 10(e- 13) M Ang II to LPS-stimulated or unstimulated lymphocytes. Ang II caused a significant upregulation of T subset lymphocytes gene expression of ACE and AT1-R and of INF gamma, and a marked increase in ACE activity and cell Ang II concentration. AGTN gene was never expressed. All these effects were further enhanced in T lymphocytes presitmulated by LPS and completely inhibited by Irbesartan. Our findings strongly support the evidence of a positive Ang II driven autocrine loop that upregulates cell RAS of isolated lymphocytes and activates the immuno response. The immuno-potentiating effect of Ang II, specifically shown in T subset, can be deleterious when local RAS are disregulated as in cardiovascular atherosclerotic disease.
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PMID:Angiotensin II upregulates renin-angiotensin system in human isolated T lymphocytes. 1872 52

Misregulation of the level of RNA polymerase II carboxyl-terminal domain (CTD) phosphatase, Fcp1, in Drosophila results in high level of caspase-mediated apoptosis. Apoptosis induction by Fcp1 misregulation requires the presence of Drosophila melanogaster (Dm)p53, but occurs without the transcriptional activation of Dmp53 proapoptotic targets rpr, ark, and hid. Overproduction of a transcription activation-defective mutant Dmp53 protein increases, while Dmp53 null background decreases significantly the level of apoptosis in Fcp1-misregulated animals. Generating the apoptotic signal does not require the function of the ATM and Rad3-related kinase (ATR), and no significant level of nucleo-cytoplasmic translocation of Dmp53 is detectable in cells expressing Fcp1 at an abnormal level. Immunostaining of larval salivary gland polytene chromosomes with anti-Dmp53 antibodies indicates Dmp53 localization at several transcriptionally active chromosomal regions in wild-type cells, while in Fcp-misregulated cells the association of Dmp53 with specific chromosomal sites is decreased.
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PMID:Misregulated RNA Pol II C-terminal domain phosphorylation results in apoptosis. 1915 63


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