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)

We have investigated the regulation of p27kip1, a cyclin-dependent kinase inhibitor, in BALB/c 3T3 cells during growth factor-stimulated transition from quiescence (G0) to a proliferative (G1) state. The level of p27kip1 protein falls dramatically after mitogenic stimulation and is accompanied by a decrease in cyclin E associated p27kip1, as well as a transient increase in cyclin D1-associated p27kip1 that later declines concomitantly with the loss of total p27kip1. Analysis of metabolically labelled cells revealed that cyclin D2, cyclin D3, and cdk4 were also partnered with p27kip1 in quiescent BALB/c 3T3 cells and that this association decreased after platelet-derived growth factor (PDGF) treatment. Furthermore, the decline in p27kip1 and reduced association with cyclin D3, initiated by the addition of PDGF but not plasma-derived factors, suggested that these changes are involved in competence, the first step in the exit from G0. Synthesis of p27kip1 as determined by incorporation of [35S]methionine was repressed upon mitogenic stimulation, and PDGF was sufficient to elicit this repression within 2 to 3 h. Pulse-chase experiments demonstrated the reduced rate of synthesis was not the result of an increased rate of degradation. Full repression of p27kip1 synthesis required the continued presence of PDGF and failed to occur in the presence of the RNA polymerase inhibitor 5,6-dichlorobenzimidazole riboside. These characteristics demonstrate that repression was a late effect of PDGF and was consistent with our finding that conditional expression of activated H-ras did not affect synthesis of p27kip1. Northern (RNA) analysis of p27kip1 mRNA revealed that the repression was not accompanied by a corresponding decrease in p27kip1 mRNA, suggesting that the PDGF-regulated decrease in p27kip1 expression occurred through a translational mechanism.
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PMID:Repression of p27kip1 synthesis by platelet-derived growth factor in BALB/c 3T3 cells. 875 33

Nuclear transcription is repressed when eukaryotic cells enter mitosis. Mitotic repression of transcription of various cellular and viral gene promoters by RNA polymerase II can be reproduced in vitro either with extracts prepared from cells arrested at mitosis with the microtubule polymerization inhibitor nocodazole or with nuclear extracts prepared from asynchronous cells and the mitotic protein kinase cdc2/cyclin B. Purified cdc2/cyclin B kinase is also sufficient to inhibit transcription in reconstituted transcription reactions with biochemically purified and recombinant basal transcription factors and RNA polymerase II. The cyclin-dependent kinase inhibitor p21Waf1/Cip1/Sdi1 can reverse the effect of cdc2/cyclin B kinase, indicating that repression of transcription is due to protein phosphorylation. Transcription rescue and inhibition experiments with each of the basal factors and the polymerase suggest that multiple components of the transcription machinery are inactivated by cdc2/cyclin B kinase. For an activated promoter, targets of repression are TFIID and TFIIH, while for a basal promoter, TFIIH is the major target for mitotic inactivation of transcription. Protein labeling experiments indicate that the p62 and p36 subunits of TFIIH are in vitro substrates for mitotic phosphorylation. Using the carboxy-terminal domain of the large subunit of RNA polymerase II as a test substrate for phosphorylation, the TFIIH-associated kinase, cdk7/cyclin H, is inhibited concomitant with inhibition of transcription activity. Our results suggest that there exist multiple phosphorylation targets for the global shutdown of transcription at mitosis.
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PMID:Repression of TFIIH transcriptional activity and TFIIH-associated cdk7 kinase activity at mitosis. 948 63

Cells expressing the R273H mutant of p53, which lacks sequence specific DNA binding capacity, do not undergo cell cycle arrest in G1 following exposure to ionizing or UV radiation because of their inability to induce p21Waf1/Cip1, a cyclin-dependent kinase inhibitor and downstream mediator of p53-dependent DNA damage-induced growth arrest. Following UV-irradiation or treatment with an inhibitor of RNA pol II, we observed a rapid induction of the apoptotic process, as evidenced by DNA fragmentation and the proteolytic cleavage of poly(ADP-ribose) polymerase. Using mimosine, a p21Waf1/Cip1 inducer that bypasses the requirement for transcriptional transactivation by p53, we demonstrated that a G1 cell cycle arrest can prevent apoptosis following UV-irradiation or treatment with an RNA polymerase 11 inhibitor. Serum starvation, which also synchronized cells in G1 but did not induce p21Waf1/Cip1, did not protect cells from apoptosis. These results demonstrate that restoring a late G1 checkpoint by inducing p21Waf1/Cip1 expression can protect cells from DNA damage induced apoptosis. Our results suggest that p21Waf1/Cip1 can interrupt the apoptotic process at a point downstream from p53 accumulation but upstream from caspase-3 activation.
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PMID:p21-induced cycle arrest in G1 protects cells from apoptosis induced by UV-irradiation or RNA polymerase II blockage. 969 54

The promoter region of the cyclin-dependent kinase inhibitor p15(INK4B) contains a CpG island that is hypermethylated in many hematologic malignancies. To explore the relationship between patterns of methylation and gene transcription, we used bisulfite genomic sequencing to obtain a detailed analysis of methylation in acute leukemia, leukemia cell lines, and normal lymphocytes. The entire CpG island region of p15 was largely devoid of methylation in normal lymphocytes, but methylation of varying density was found in primary acute leukemia. Methylation density was generally conserved between the alleles from each sample, but marked heterogeneity for the specific CpG sites methylated was observed. Patterns of methylation were compared and expression assessed with reverse-transcriptase polymerase chain reaction (RT-PCR). The density of methylation within the CpG island, and not any specific location, correlates best with transcriptional loss. Leukemias with methylation of approximately 40% of the CpG dinucleotides on each allele had complete gene silencing, with variable, but diminished expression with less dense CpG island methylation. Our results suggest that the transcriptional silencing of p15 in conjunction with aberrant hypermethylation is best understood as an evolutionary process that involves progressively increasing methylation of the entire p15 CpG island.
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PMID:p15(INK4B) CpG island methylation in primary acute leukemia is heterogeneous and suggests density as a critical factor for transcriptional silencing. 1049 17

The DNA topoisomerase I (topI) inhibitor camptothecin (CPT), stabilizes so-called cleavable complexes which consist of topI covalently attached to 3' OH ends of DNA nicks. Collisions between the progressing DNA replication forks (occurring in S phase cells) or between the transcription driven RNA polymerase molecules (occurring in G1, S and G2 cells) and these complexes convert the latter into secondary DNA lesions which are unrepairable and lethal to the cell. Changes induced by CPT in the level of the tumor suppressor p53, cyclin-dependent kinase inhibitor p21WAF1 and proapoptotic protein Bax (all detected immunocytochemically), were measured separately in the nucleus and cytoplasm of individual human breast carcinoma MCF-7 cells by laser scanning cytometry (LSC) in relation to cell cycle position and induction of apoptosis. The initial transient cell arrest at the G1 checkpoint seen at 8-16 h of treatment with 0.15 microM CPT was accompanied by the rapid accumulation of p53 (preventable by cycloheximide) in the nucleus; the rise (>20-fold) in p53 was maximal for S phase cells. The magnitude of the nuclear p53 increase induced by CPT, at maximum, was 2-fold higher than that induced by the proteasome inhibitor N-acetyl-Leu-Leu-norleucinal (LLnL). While the accumulation of p53 was seen in all phases of the cycle, only G1 cells responded by induction ( approximately 60-fold increase) of p21WAF1. Inhibition of DNA replication by aphidicolin prevented the accumulation of p53 in S and G2/M but had no effect on its induction in G1 cells. Perturbation of cell progression through S phase was seen between 24-72 h of treatment, and it coincided with induction of Bax and apoptosis (both maximal in S phase cells). Thus, the changes observed in S phase cells (nuclear accumulation of p53 preventable by aphidicolin, induction of Bax, apoptosis), triggered by the collisions of DNA replication forks with the CPT-induced lesions, were distinct from the changes in G1 (nuclear p53 accumulation unaffected by aphidicolin, induction of p21WAF1) presumably triggered by collisions of RNA polymerase with the CPT-lesions. Great heterogeneity in expression of p53 and p21WAF1 of the G1 cell population in response to CPT was observed, which may reflect the intercellular variability in the rate of transcription (i.e., frequencies of collisions of RNA polymerase with the lesions). Thus, differences in the transcriptional activity of G1 cells may play a role in their sensitivity to CPT and similar topI inhibitors.
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PMID:Differences in induction of p53, p21WAF1 and apoptosis in relation to cell cycle phase of MCF-7 cells treated with camptothecin. 1053 67

Erythema multiforme follows administration of several drugs or infection with various agents, including herpes simplex virus, a syndrome designated herpes simplex virus associated erythema multiforme. Lesional skin from 21 of 26 (81%) herpes simplex virus associated erythema multiforme patients was positive for herpes simplex virus gene expression as evidenced by reverse transcriptase-polymerase chain reaction with primers for DNA polymerase and/or immunohistochemistry with DNA polymerase antibody. Reverse transcriptase-polymerase chain reaction and immunohistochemistry studies indicated that herpes simplex virus associated erythema multiforme lesional skin from 16 of 21 (76%) DNA polymerase positive herpes simplex virus associated erythema multiforme patients was also positive for interferon-gamma, a product of T cells involved in delayed-type hypersensitivity (p < 0. 0001 by Pearson correlation coefficient). Interferon-gamma signals were in infiltrating mononuclear cells and in intercellular spaces within inflammatory sites in the epidermis and at the epidermis/dermis junction. Herpes simplex virus lesional skin was also positive for DNA polymerase [five of five (100%)] and interferon-gamma [four of five (80%)], but lesional skin from drug-induced erythema multiforme patients was negative. Lesional herpes simplex virus associated erythema multiforme keratinocytes also stained with antibody to transforming growth factor-beta [14 of 23 (61%)] and cyclin-dependent kinase inhibitor waf [12 of 18 (67%)]. Staining was also seen in keratinocytes from herpes simplex virus lesions [five of five (100%)], but not in normal skin. By contrast, staining with antibody to tumor necrosis factor-alpha, another pro-inflammatory cytokine, was seen in seven of 11 (64%) drug-induced erythema multiforme patients, but not in herpes simplex virus or herpes simplex virus associated erythema multiforme patients, and lesional keratinocytes from drug-induced erythema multiforme patients were negative for transforming growth factor-beta and cyclin-dependent kinase inhibitor waf. We interpret the data to indicate that herpes simplex virus associated erythema multiforme pathology includes a delayed-type hypersensitivity component and is mechanistically distinct from drug-induced erythema multiforme.
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PMID:Herpes simplex virus associated erythema multiforme (HAEM) is mechanistically distinct from drug-induced erythema multiforme: interferon-gamma is expressed in HAEM lesions and tumor necrosis factor-alpha in drug-induced erythema multiforme lesions. 1057 38

Multiple myeloma (MM) is a B-cell malignancy characterized by the accumulation of malignant plasma cells with slow proliferative rate but enhanced survival. MM cells express multiple Bcl-2 family members, including Bcl-2, Bcl-XL, and Mcl-1, which are thought to play a key role in the survival and drug resistance of myeloma. The cyclin-dependent kinase inhibitor flavopiridol has antitumor activity against hematopoietic malignancies, including CLL, in which induction of apoptosis was associated with reduced expression of antiapoptotic proteins. Therefore, we sought to characterize the effect of flavopiridol on the proliferation and survival of myeloma cells and to define its mechanisms of action. Treatment of MM cell lines (8226, ANBL-6, ARP1, and OPM-2) with clinically achievable concentrations of flavopiridol resulted in rapid induction of apoptotic cell death that correlated temporally with the decline in Mcl-1 protein and mRNA levels. Levels of other antiapoptotic proteins did not change. Overexpression of Mcl-1 protected MM cells from flavopiridol-induced apoptosis. Additional analysis demonstrated that flavopiridol treatment resulted in a dose-dependent inhibition of phosphorylation of the RNA polymerase II COOH-terminal domain, thus blocking transcription elongation. These data indicate that Mcl-1 is an important target for flavopiridol-induced apoptosis of MM that occurs through inhibition of Mcl-1 mRNA transcription coupled with rapid protein degradation via the ubiquitin-proteasome pathway.
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PMID:The cyclin-dependent kinase inhibitor flavopiridol induces apoptosis in multiple myeloma cells through transcriptional repression and down-regulation of Mcl-1. 1242 44

The effects of all trans retinoic acid and hyperthermia were studied in the human colon adenocarcinoma cell line HT29. Cell cytotoxicity after exposure to ATRA or heat-shock, alone or in association, was evaluated by the MTT assay while cell surface and ultrastructure modifications and actin fibre assembly changes were investigated by electron microscopy and by the FITC-phalloidin method. Apoptosis was evaluated by flow cytofluorimetry and electron microscopy. Reverse transcriptase-polymerase chain reaction was employed to study mRNA expression of genes involved in apoptosis, differentiation and growth arrest. Joint treatments were more effective in reducing the vital cell yield, being this effect only partially due to apoptosis. A marked up-regulation of the cyclin-dependent kinase inhibitor p21WAF1/Cip1 expression, not followed by any differentiation process, was responsible for growth arrest. Modulation of Hsp-70 expression, involved in cell response to treatments, was considered. Our results demonstrate that cell treatment with ATRA followed by heat-shock may elicit useful effects to treat tumours, which are responsive to retinoids, as well as those malignant cells which may be constitutively thermotolerant.
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PMID:All trans retinoic acid sensitizes colon cancer cells to hyperthermia cytotoxic effects. 1279 92

Che-1 is a recently identified human RNA polymerase II binding protein involved in the regulation of gene transcription and cell proliferation. We previously demonstrated that Che-1 inhibits the Rb growth-suppressing function by interfering with Rb-mediated HDAC1 recruitment on E2F target gene promoters. By hybridization of cancer profile arrays, we found that Che-1 expression is strongly down-regulated in several tumors, including colon and kidney carcinomas, compared with the relative normal tissues. Consistent with these data, Che-1 overexpression inhibits proliferation of HCT116 and LoVo human colon carcinoma cell lines by activation of the cyclin-dependent kinase inhibitor p21WAF1/Cip1 in a p53-independent manner and by promoting growth arrest at the G1 phase of the cell cycle. Che-1 activates p21WAF1/Cip1 by displacing histone deacetylase (HDAC)1 from the Sp1 binding sites of the p21WAF1/Cip1 gene promoter and accumulating acetylated histone H3 on these sites. Accordingly, Che-1-specific RNA interference negatively affects p21WAF1/Cip1 transactivation and increases cell proliferation in HCT116 cells. Taken together, our results indicate that Che-1 can be considered a general HDAC1 competitor and its down-regulation is involved in colon carcinoma cell proliferation.
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PMID:Che-1 arrests human colon carcinoma cell proliferation by displacing HDAC1 from the p21WAF1/CIP1 promoter. 1284 90

B-cell chronic lymphocytic leukemia (B-CLL) is a clinically variable disease where mutations in DNA damage response genes ATM or TP53 affect the response to standard therapeutic agents. The in vitro cytotoxicity of a novel cyclin-dependent kinase inhibitor, CYC202, was evaluated in 26 B-CLLs, 11 with mutations in either the ATM or TP53 genes, and compared with that induced by ionizing radiation and fludarabine. CYC202 induced apoptosis within 24 hours of treatment in all 26 analyzed tumor samples independently of ATM and TP53 gene status, whereas 6 of 26 B-CLLs, mostly ATM mutant, showed marked in vitro resistance to fludarabine-induced apoptosis. Compared with B-CLLs, normal T and B lymphocytes treated with CYC202 displayed reduced and delayed apoptosis. Using global gene expression profiling, we found that CYC202 caused a significant down-regulation of genes involved in regulation of transcription, translation, survival, and DNA repair. Furthermore, induction of apoptosis by CYC202 was preceded by inhibition of RNA polymerase II phosphorylation, leading to down-regulation of several prosurvival proteins. We conclude that CYC202 is a potent inducer of apoptosis in B-CLL regardless of the functional status of the p53 pathway, and may be considered as a therapeutic agent to improve the outcome of resistant B-CLL tumors.
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PMID:A novel CDK inhibitor, CYC202 (R-roscovitine), overcomes the defect in p53-dependent apoptosis in B-CLL by down-regulation of genes involved in transcription regulation and survival. 1569 65


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