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:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Epigenetic alterations in the genome of tumor cells have attracted considerable attention since the discovery of widespread alterations in DNA methylation of colorectal cancers over 10 years ago. However, the mechanism of these changes has remained obscure. el-Deiry and coworkers [el-Deiry, W. S., Nelkin, B. D., Celano, P., Yen, R. C., Falco, J. P., Hamilton, S. R. & Baylin, S. B. (1991) Proc. Natl. Acad. Sci. USA 88, 3470-3474], using a quantitative reverse transcription-PCR assay, reported 15-fold increased expression of DNA methyltransferase (MTase) in colon cancer, compared with matched normal colon mucosa, and a 200-fold increase in MTase mRNA levels compared with mucosa of unaffected patients. These authors suggested that increases in MTase mRNA levels play a direct pathogenetic role in colon carcinogenesis. To test this hypothesis, we developed a sensitive quantitative RNase protection assay of MTase, linear over three orders of magnitude. Using this assay on 12 colorectal carcinomas and matched normal mucosal specimens, we observed a 1.8- to 2.5-fold increase in MTase mRNA levels in colon carcinoma compared with levels in normal mucosa from the same patients. There was no significant difference between the normal mucosa of affected and unaffected patients. Furthermore, when the assay was normalized to histone H4 expression, a measure of S-phase-specific expression, the moderate increase in tumor MTase mRNA levels was no longer observed. These data are in contrast to the previously reported results, and they indicate that changes in MTase mRNA levels in colon cancer are nonspecific and compatible with other markers of cell proliferation.
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PMID:Limited up-regulation of DNA methyltransferase in human colon cancer reflecting increased cell proliferation. 881 6

The efficacy of chemoprevention trials can be improved by the use of biomarkers of carcinogenesis that serve as surrogate end points. The aim of this study was to assess the perspectives of using mRNA isolated from oral exfoliated cells for biomarker research in chemoprevention of upper aerodigestive tract cancer. When using reverse transcription-PCR in combination with Southern blotting and hybridization, it was possible to detect transcripts from only five cells. With the quantitative RNase protection assay, we could only detect highly abundant transcripts. The integrity of the RNA was verified by Northern blotting, which showed a variable degree of degradation, depending on the gene studied. Interestingly, although specific transcripts were found to be intact to a certain extent, the rRNA appeared to be completely degraded, suggesting that a specific protein synthesis shut-off mechanism exists in terminally differentiated oral epithelial cells. Altogether, this differential RNA degradation makes accurate measurement of transcript levels of most genes, as determined in exfoliated oral cells, unreliable. Because this RNA degradation process is likely to start before the cells are shed from the tissue, the results of measurements of transcript levels in biopsies of oral tissue should be interpreted with caution.
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PMID:Exfoliated oral cell messenger RNA: suitability for biomarker studies. 964 89

Telomerase, a ribonucleoprotein complex that includes the telomerase RNA component (hTR) and the telomerase catalytic subunit gene (hTERT) product, has been shown to be activated in the majority of cancer tissues and immortalized cells. To study telomerase activation during the progression of cervical cancer, the expression of hTR and hTERT RNAs in tissues of various stages of cervical cancer was analyzed using the in situ hybridization method and compared with proliferative activity as estimated by Ki-67 immunostaining. To test whether expression of these components is reflected in enzyme activity, we determined the levels of the RNAs in cervical cancer and normal tissues and in primary and immortal keratinocytes by reverse transcription-polymerase chain reaction and RNase protection assays and compared the results to telomerase activities as detected by telomeric repeat amplification protocol assay. In situ hybridization signals of hTR and hTERT were present not only in carcinoma tissues but also in normal epidermal layers. In many adenocarcinoma and fewer squamous cell carcinoma tissues, both signals were focally increased where high proliferative activity was present at the stages of dysplasia/metaplasia, in situ carcinoma, and invasive carcinoma. The level of bTERT, as quantitated by RNase protection assay, was not different between cancer and control tissues or immortal and a subset of primary keratinocytes and did not correlate with telomerase activity. These results indicate that expression of hTR and bTERT is up-regulated in at least a subset of neoplastic cells at an early stage of carcinogenesis and that unidentified factors, such as the modulation or coordination of its protein level with other products, may contribute to the activation of telomerase in cervical cancer.
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PMID:Telomerase activity and expression of telomerase RNA component and telomerase catalytic subunit gene in cervical cancer. 973 34

Differential display PCR [DD-PCR] was applied to identify mRNAs differentially expressed between two consecutive stages of an in vivo model of mouse mammary carcinogenesis. The extended life 12 [EL12] and transformed mammary 12 [TM12] outgrowths differ in morphology, ovarian hormone dependence, and tumorigenicity, yet the TM12 outgrowth arose spontaneously from the EL12 outgrowth. A fragment of the mouse p96 gene was identified using DD-PCR. The differential expression of p96 was confirmed using RNase protection assays. Examination of the RNA expression patterns of the p96 isoforms during normal mammary gland development showed high levels in the involuting mammary gland and in preneoplastic hyperplasias. In contrast, p96 isoform mRNA levels were consistently decreased in mammary tumors derived from the in vivo hyperplasias. Examination of p96 protein levels revealed a decrease in p96 protein in a number of mammary tumors as compared to their hyperplastic precursors further supporting the observations that p96 gene expression is consistently downregulated in mammary tumors. The functional activity of p96 protein has not been resolved, however the observation that p96 gene expression is downregulated in two different tumor systems (human ovarian tumors and mouse mammary tumors) warrants more extensive investigation on its role in normal and neoplastic cell growth.
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PMID:p96, a MAPK-related protein, is consistently downregulated during mouse mammary carcinogenesis. 976 28

Human dihydrodiol dehydrogenase (DD) isoforms are aldo-keto reductases (AKRs) that activate polycyclic aromatic hydrocarbons (PAHs) by oxidizing trans-dihydrodiol proximate carcinogens to reactive and redox-active ortho-quinones. Of these, human AKR1C1 (DD1) and AKR1C2 (DD2) oxidize trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene to the cytotoxic and genotoxic metabolite benzo[a]pyrene-7,8-dione (BPQ) with the highest catalytic efficiency. Exposure of HepG2 cells to a panel of inducers revealed that mRNA encoding one or more human AKR1C member(s) was induced (3- to 10-fold) by benzo[a]pyrene and other polycyclic aromatic compounds (bi-functional inducers), electrophilic Michael acceptors and phenolic antioxidants (monofunctional inducers), and reactive oxygen species (ROS). The induction of AKR1C mRNA by bifunctional inducers was delayed with respect to the induction of CYP1A1 mRNA, and AKR1C mRNA was not induced by the nonmetabolizable aryl hydrocarbon receptor ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). These data suggest that, in contrast to the CYPs, induction of AKR1C member(s) by PAHs and other bifunctional inducers is mediated indirectly via an antioxidant response element rather than a xenobiotic response element. Immunoblot and enzymatic assays confirmed that the increases in AKR1C mRNA were faithfully translated into functional AKR1C protein(s). The increased DD activity in HepG2 lysates was inhibited only by high concentrations of ursodeoxycholate, which suggested that AKR1C2 (DD2, bile-acid-binding protein) was not the isoform induced. RNase protection assays identified AKR1C1 (DD1) mRNA as the transcript which was up-regulated by mono- and bi-functional inducers and ROS in both human hepatoma (HepG2) and colon carcinoma (HT29) cells. BPQ, the electrophilic and redox-cycling product of the AKR1C1 reaction, also induced AKR1C1 expression. Thus, BPQ formation by AKR1C1 results in both a chemical (redox-cycling) and a genetic (AKR1C1 induction) amplification of ROS in PAH-exposed cells. Because ROS have been implicated in both tumor initiation and tumor promotion, the amplification of ROS by this pathway may play a significant role in PAH carcinogenesis.
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PMID:Isoform-specific induction of a human aldo-keto reductase by polycyclic aromatic hydrocarbons (PAHs), electrophiles, and oxidative stress: implications for the alternative pathway of PAH activation catalyzed by human dihydrodiol dehydrogenase. 997 8

Peroxisomes and the activities of their enzymes have been reported to be significantly reduced in various types of tumors including the colon carcinoma. Therefore, the present study was designed to investigate the gene expression of several peroxisomal proteins in human colon carcinoma and additionally those of the peroxisome proliferator activated receptor alpha (PPARalpha) and PEX5, a receptor protein involved in the import of most peroxisomal matrix proteins. Samples from adenocarcinomas and adjacent normal colon were analyzed by immunohistochemistry and western blotting. The mRNA content was assessed by a novel sensitive dot blot RNase protection assay and northern blotting. By immunohistochemistry, peroxisomes were distinctly visualized in normal colonocytes but were not detected in colon carcinoma cells. The protein levels of catalase (CAT), acyl-CoA oxidase as well as the 22 and 70 kDa peroxisomal membrane proteins (PMP22 and PMP70) were all significantly decreased in carcinomas. The corresponding mRNAs for CAT and PMP70, however, were unchanged. In contrast, the mRNA of PEX5 was significantly increased. The expression of PPARalpha was not altered in tumors, neither at protein nor mRNA levels. These observations show that the reduction of peroxisomes and their proteins in colon carcinoma is not due to a generalized reduction of transcription of their genes. It seems more likely that this phenomenon is regulated at a post-transcriptional or translational level. Alternatively, and more likely, an impairment of the biogenesis of the organelle could account for the paucity of peroxisomes in colon carcinoma.
Carcinogenesis 1999 Jun
PMID:Impairment of peroxisomal biogenesis in human colon carcinoma. 1035 77

Epidemiology suggests a possible relationship between exposure to power frequency magnetic fields (EMF) and breast cancer. One mechanism through which EMF could stimulate breast cancer induction is via altered expression of oncogenes and/or tumor suppressor genes that regulate normal and neoplastic growth. To evaluate the hypothesis that EMF action in the breast is mediated by alterations in gene expression, transcript levels of c-myc and a battery of other cancer-associated genes were quantitated in human breast epithelial cells exposed to pure, linearly polarized 60 Hz EMF with low harmonic distortion. HBL-100 cells and normal (non-transformed) human mammary epithelial cells were exposed to EMF flux densities of 0.1, 1.0 and 10.0 Gauss (G) for periods ranging from 20 min to 24 h; concurrent sham controls were exposed to ambient fields (<0.001 G) only. Gene expression was quantitated using ribonuclease protection assays. EMF exposure had no statistically significant effect on basal levels of c-myc transcripts in either human breast cell model, and had no effect on alterations in c-myc expression induced by 12-O-tetradecanoylphorbol-13-acetate. Transcript levels of c-erbB-2, p53, p21, GADD45, bax, bcl-x, mcl-1, and c-fos were also unaffected by EMF exposure. These results suggest that EMF is unlikely to influence breast cancer induction through a mechanism involving altered expression of these genes.
Carcinogenesis 1999 Aug
PMID:Gene expression in human breast epithelial cells exposed to 60 Hz magnetic fields. 1042 19

Peroxisome proliferator-activated receptor binding protein (PBP), a nuclear receptor coactivator, interacts with estrogen receptor alpha (ERalpha) in the absence of estrogen. This interaction was enhanced in the presence of estrogen but was reduced in the presence of antiestrogen, tamoxifen. Transfection of PBP in CV-1 cells resulted in enhancement of estrogen-dependent transcription, indicating that PBP serves as a coactivator in ER signaling. To examine whether overexpression of PBP plays a role in breast cancer because of its coactivator function in ER signaling, we determined the levels of PBP expression in breast tumors. High levels of PBP expression were detected in approximately 50% of primary breast cancers and breast cancer cell lines by ribonuclease protection analysis, in situ hybridization, and immunoperoxidase staining. Fluorescence in situ hybridization of human chromosomes revealed that the PBP gene is located on chromosome 17q12, a region that is amplified in some breast cancers. We found PBP gene amplification in approximately 24% (6/25) of breast tumors and approximately 30% (2/6) of breast cancer cell lines, implying that PBP gene overexpression can occur independent of gene amplification. This gene comprises 17 exons that, together, span >37 kilobases. The 5'-flanking region of 2.5 kilobase pairs inserted into a luciferase reporter vector revealed that the promoter activity in CV-1 cells increased by deletion of nucleotides from -2,500 to -273. The -273 to +1 region, which exhibited high promoter activity, contains a typical CCAT box and multiple cis-elements such as C/EBPbeta, YY1, c-Ets-1, AP1, AP2, and NFkappaB binding sites. These observations, in particular PBP gene amplification, suggest that PBP, by its ability to function as ERalpha coactivator, might play a role in mammary epithelial differentiation and in breast carcinogenesis.
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PMID:Amplification and overexpression of peroxisome proliferator-activated receptor binding protein (PBP/PPARBP) gene in breast cancer. 1048 14

To understand the expression and role of thyroid hormone nuclear receptors (TRs) in hepatocarcinogenesis, we characterized the TRs in 16 human hepatocellular carcinoma (HCC) specimens. The full-length cDNAs for the two TR subtypes, alpha1 and beta1, were cloned from several tumors by reverse transcription-polymerase chain reaction. Southern blot analysis indicated that, in addition to the full-length cDNA, truncated TRalpha1 and TRbeta1 cDNAs were present in nine tumors (53%). In addition, point mutations detected by the mismatch RNase cleavage assay in TRalpha1 and TRbeta1 were found in 65% and 76% of the tumors, respectively. The mutations were confirmed by DNA sequencing. Interestingly, most of the TRalpha1 mutations were in amino acid codons 209-228 and 245-256, two hot-spots in HCC patients. However, no hot-spot was detected in TRbeta1. The expression of TRalpha1 and TRbeta1 proteins was determined in the tissue extracts by western blotting. TRbeta1 protein was expressed or elevated in 10 tumors but not in normal livers, whereas the expression of TRalpha1 was variable among tumors. The mutant TR proteins were translated in vitro, and their hormone- and DNA-binding activities were evaluated. Abnormal binding to the thyroid hormone response elements was observed. The proteins' DNA binding activity was either partially impaired or completely lost. The high prevalence of TR mutations found in the tumors of patients with hepatocellular carcinoma suggests that mutant TRs could play an important role in liver carcinogenesis.
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PMID:Expression of mutant thyroid hormone nuclear receptors in human hepatocellular carcinoma cells. 1048 22

The oppositely-imprinted genes insulin-like growth factor-II (IGF2) and H19, a putative tumor suppressor, often show coordinate, reciprocal regulation and are believed to play a role in carcinogenesis. To explore the possible interactions between these genes, we stably transfected diHepG2 cells with a plasmid containing either the sense or the antisense H19 cDNA sequences and verified their expression by Northern analysis and by RNase protection analysis. Levels of H19, IGF2 and gamma-actin mRNA were quantified by competitive RT-PCR analysis. Although H19 sense transgene overexpression (n = 24 clones) did not decrease the low, basal levels of IGF2 mRNA compared to control cells, levels of IGF2 mRNA were positively correlated with the levels of H19 antisense mRNA (P < 0.0001, n = 40 clones). Furthermore, the increase in IGF2 mRNA level was accompanied by an elevation of IGF-II peptide in conditioned media. To see if H19 mRNA had a specific effect on transcription, we also performed transient transfections with reporter gene constructs containing IGF2 promoter 3 in the presence of sense or antisense H19 cDNA sequences under control of a cytomegalovirus promoter. We show a lower reporter gene activity from reporter gene constructs in the presence of sense H19 cDNA than from those with antisense or neomycin. Our results suggest that H19 participates in the repression of IGF2, at least in part through effects on IGF2 transcription, an effect which may contribute to its action as a tumor suppressor.
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PMID:H19 sense and antisense transgenes modify insulin-like growth factor-II mRNA levels. 1086 1


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