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:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The polymerase chain reaction was used to amplify genomic DNA and reverse-transcribed RNA from human lymphocytes, using primers derived from conserved regions within the retroviral reverse transcriptase. Sequencing of 33 cloned amplification products revealed that a variety of sequences with similarity to mouse mammary tumor virus, mouse intracisternal A particle, and human endogenous retrovirus K10 were detected with this primer pair. The sequences were divided into six subgroups, with a nucleotide sequence dissimilarity of about 25% between the subgroups. Members within five of the subgroups were most closely related to human endogenous retrovirus K10 and mouse mammary tumor virus, whereas sequences of the sixth subgroup also showed similarity to mouse intracisternal A particle. Ten of the sequences had open reading frames with preference for silent mutations at conserved sites. Southern blot analysis showed that some HML (human endogenous MMTV-like) subgroups (HML-4 and HML-5) were present in a few copies (about 5), whereas others (HML-1 to HML-3 and HML-6) were present in at least 10 to 20 copies per genome. Northern (RNA) blot analysis revealed that several of the subgroups are differentially expressed in human normal tissues. A complex pattern of transcripts from about 12 to 1.4 kb was found in several of the tissues tested. However, the most abundant expression was detected in lung (all subgroups), skeletal muscle (HML-4 and HML-5), placenta (HML-2 and HML-5), and kidney (HML-2, HML-3 and HML-5). Expression of reverse transcriptase sequences in human tissues may have biological consequences. The described sequences are similar to elements which cause carcinoma and are immunoregulatory in mice. It remains to be seen whether human sequences also have such functions.
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PMID:Characterization of novel reverse transcriptase encoding human endogenous retroviral sequences similar to type A and type B retroviruses: differential transcription in normal human tissues. 769 84

Wild-type as well as variant oestrogen receptor (ER) mRNAs with exon 5 and 7 deleted were identified in a panel of human breast tumour cell lines by reverse transcriptase-polymerase chain reaction followed by dideoxynucleotide sequence analysis, and then quantitated by ribonuclease protection analysis. All cell lines categorised as ER+ by ligand-binding analysis expressed both wild-type and variant ER transcripts. Most cell lines classified as ER- did not express any ER transcript. However, three ER- cell lines (BT-20, MDA-MB-330 and T47Dco) expressed both wild-type and variant transcripts. A differential pattern of expression of wild type to variant was seen in both ER+ and ER- cell lines, however this pattern was not paralleled by differences in ligand-binding activity. Breast tumour cell lines previously classified as ER- expressed significantly lower levels of ER transcripts than did their ER+ counterparts. In view of these findings, as well as earlier reports that the exon 5 deletion ER variant encodes a dominant-positive receptor, it seems clear that some cell lines are misclassified as ER-, and express both wild-type and variant ER mRNAs, and that the overexpression of this variant may account, in part, for their oestrogen-independent phenotype.
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PMID:Coexpression of wild-type and variant oestrogen receptor mRNAs in a panel of human breast cancer cell lines. 773 23

Human (U251, U87, U343) and rat glioma cell lines (C6, 9L) were examined by the reverse transcriptase-polymerase chain reaction and subsequent nucleotide sequencing analysis to see whether they express wild type (wt)-p53 or mutated form (mut)-p53 messages. Results showed that U87, U343, and C6 cells expressed wt-p53 messages whereas U251 and 9L cells expressed mut-p53 messages. All these cell lines were transfected with wt-p53 cDNA or the s-myc gene linked to the mouse mammary tumor virus (MMTV) promoter. Of several G418-resistant clones obtained from each transfection, a few expressed the s-Myc or wt-p53 proteins. Independent of mutations in the intrinsic p53 gene, the cellular growth in vitro and tumorigenicity in nude mice of these clones were drastically suppressed, the extent of suppression being correlated with the expression level of the transfected gene. Flow-cytometric analysis demonstrated that both p53 and s-Myc arrested the cell cycle at the G1/S boundary. These data suggest that these genes having negative effects on tumor cell proliferation could be used in gene therapy of gliomas, which are caused by alteration of the p53 gene or by some other genetic change.
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PMID:Negative effects of wild-type p53 and s-Myc on cellular growth and tumorigenicity of glioma cells. Implication of the tumor suppressor genes for gene therapy. 780 77

The nonsteroidal antiestrogen tamoxifen (TAM) is used to treat receptor-positive breast cancer and is now being evaluated for prophylaxis of "high-risk" population. The present study seeks to examine mechanisms that may be critical for prophylactic effects of TAM on transformation-sensitive mammary tissue. The experimental systems utilized included: in vivo rodent models for mammary tumorigenesis and in vitro cell culture models for preneoplastic transformation. In the in vivo models TAM suppressed constitutive, as well as carcinogen-induced proliferation, expression of mammary tumor virus-associated reverse transcriptase activity and decreased the incidence and frequency of mammary hyperplastic alveolar nodules. In the in vitro models TAM suppressed carcinogen-induced DNA damage, altered cellular metabolism of estradiol favoring the formation of less estrogenic catechols, and down-regulated anchorage-independent growth that is induced by ras oncogene and chemical carcinogen. Effective down-regulation of specific proliferative and metabolic biomarkers that are perturbed in mammary cell prior to tumorigenesis provides evidence that altered cellular metabolism of E2 may, in part, be responsible for antiproliferative and prophylactic properties of TAM against mammary tumorigenesis.
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PMID:Effect of tamoxifen on mammary preneoplasia: relevance to chemopreventive intervention. 798 41

The complete nucleotide sequence of the dwarf hamster endogenous retrovirus (MRS-Ps) related to the mouse mammary tumor virus is presented. MRS-Ps has a typical retroviral structure, it is 6980 bp long with LTRs of ca. 880 base pairs at both ends. LTRs carry the usual signals for transcription control. MRS-Ps genes had formerly coded for viral proteins (protease, revertase, and envelope proteins) but have been spoiled by numerous point mutations. Evolutionary relationships with other retroviruses are discussed on the basis of computer analysis of the MRS-Ps sequence.
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PMID:[Analysis of the sequence of the endogenous Djungarian hamster provirus (MRS-Ps) related to the murine mammary cancer virus]. 799 Aug 18

Transgenic female mice bearing human transforming growth factor-alpha (TGF alpha) cDNA under the control of the mouse mammary tumor virus enhancer/promoter became pregnant but failed lactation. TGF alpha mRNA was detected in the mammary glands of these mice by the reverse transcriptase-polymerase chain reaction. By the use of collagenase-dissociated mammary epithelial cells, the binding of prolactin to its receptor was determined before and after parturition. At the end of pregnancy, the binding in TGF alpha transgenic (TGF alpha [+]) mice was small and its amount was comparable to that in the TGF alpha negative (TGF alpha [-]) mice. On the day of parturition, prolactin binding in TGF alpha (+) mice increased approximately 1.9-fold (insignificant), while that in TGF alpha (-) mice elevated over 5.3-fold (P < 0.01). The binding sites per cell were also higher in TGF alpha (-)mice. Radioimmunoassay of prolactin suggested that in TGF alpha (+) mice the low level of prolactin binding after parturition was not due to masking effect of serum prolactin. Among six TGF alpha (+) mice assayed, one mother with the highest prolactin binding activity (3.7-fold increase) initiated lactation, but the others did not. As there was little difference between groups in the growth and synthesis in the mammary glands, it was concluded that the failure of lactation in TGF alpha (+) mice is principally due to the lack of elevation of mammary prolactin receptor after parturition. At present, the role of TGF alpha in this process is obscure; however, TGF alpha was revealed not to interfere with the binding of prolactin to the receptor.
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PMID:Cause of failure of lactation in mouse mammary tumor virus/human transforming growth factor alpha transgenic mice. 817 Oct 44

We have examined the human mammary tumor cell line T47D and have found that these cells produce virus-like particles which band at the typical density for retroviral particles on a sucrose gradient, possess reverse transcriptase activity, and package HERV-K10-like sequences. Using this information and a bacterial expression system to identify long open reading frames, we have identified individual clones which have full-length open reading frames for reverse transcriptase and RNase H and which could encode the reverse transcriptase activity detected in these cells.
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PMID:Human endogenous retrovirus expression and reverse transcriptase activity in the T47D mammary carcinoma cell line. 864 2

Tolerance against superantigens (SAgs) encoded by endogenous mouse mammary tumor virus (Mtv) loci involves the intrathymic deletion of SAg-reactive T cells expressing a particular TCR V beta-chain, presumably upon presentation of the SAg by specialized APC. However, although the role of dendritic cells (DC) in the induction of tolerance against conventional Ags has been demonstrated, little is known about the role played by DC in tolerance induction against Mtv SAgs. Moreover, there is conflicting evidence concerning the capacity of DC to express and present Mtv SAgs. In this report we have analyzed the expression of Mtv SAgs in highly purified thymic and splenic DC and B cells by reverse transcriptase-PCR, using primers amplifying Mtv SAg-specific spliced mRNAs. DC express Mtv SAgs at levels comparable to B cells, but display a differential expression pattern of the various Mtv loci compared with B cells. Furthermore, our results show that DC are able to induce the deletion of SAg-reactive thymocytes in an in vitro assay, indicating that Mtv SAgs are functionally expressed on the DC surface. Collectively, our data are consistent with the hypothesis that DC play a role in the induction of intrathymic tolerance to Mtv SAgs.
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PMID:Expression and presentation of endogenous mouse mammary tumor virus superantigens by thymic and splenic dendritic cells and B cells. 881 81

We have developed a reverse transcriptase-polymerase chain reaction (RT-PCR) assay to identify breast carcinoma cells in bone marrow aspirates with high sensitivity and specificity. This assay relies on the detection of cytokeratin 19 (K19) RNA by nested primer PCR followed by annealing to a (32P)-labeled internal sequence probe and autoradiography. In reconstitution experiments, this assay is capable of detecting 10 fg of admixed mammary tumor RNA in 1 microgram of normal marrow RNA (a dilution of 1:10(7)). Thirty of 30 primary breast tumor specimens, 19 of 19 cytologically positive bone marrow aspirate specimens, and three of 11 aspirate negative/biopsy positive specimens showed detectable K19 transcript. This assay shows high specificity, with 50 of 52 negative control aspirates showing no detectable amplification product. False-positive amplification was noted in two of 18 aspirates obtained from patients with active chronic myelogenous leukemia. Of stage II and III postsurgical breast carcinoma patients with histologically negative bone marrows and no radiographic bone disease, 14 of 30 were K19 positive by PCR. RT-PCR analysis of K19 transcript is a highly sensitive and specific method of detecting and monitoring low-level metastatic disease in patients with primary carcinoma of the breast. The presence of K19 RNA in histologically negative bone marrows suggests that this assay may prove a powerful monitor for patients undergoing curative therapy as well as a novel prognostic indicator.
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PMID:High-sensitivity detection of minimal residual breast carcinoma using the polymerase chain reaction and primers for cytokeratin 19. 886 30

In the experiment of mouse transforming growth factor alpha (TGF alpha) gene expression in mammary tumors, various sizes of amplified products by reverse transcriptase-polymerase chain reaction (RT-PCR) using mouse TGF alpha primers were detected in addition to a predicted size in four strains of mice. During the further analysis of these RT-PCR products in mouse mammary tumors, the transcript of neurocan gene was detected in the mammary tumor from SHN mice by the cloning and nucleotide sequence analysis after RT-PCR reaction using mouse TGF alpha primers. The 5'-nucleotide sequence of sequential 246bp in the amplified cDNA of 527bp was completely identical to a middle part of mouse neurocan cDNA sequence, one of the chondroitin-sulfate proteoglycan expressed in the nervous tissue.
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PMID:The mRNA expression of neurocan, a brain-specific chondroitin sulfate proteoglycan, in neoplastic mammary glands in mice. 900 55


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