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:2.7.7.48 (transcriptase)
9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have detected multiple forms of RNA transcript from APC, the gene which is responsible for familial adenomatous polyposis (FAP). Transcriptional initiation occurs at three sites in two distinct non-translating exons at the 5' end of the gene. At least five different forms of 5' non-coding sequences, generated by alternative splicing, exist. The splicing mechanism seems to be regulated in a tissue-specific fashion, and one type of transcript contained an additional exon, which was transcribed specifically in brain. Analyses of mRNAs from two colorectal-tumor cell lines by reverse-transcriptase polymerase chain reaction (RT-PCR) revealed that one or another of the transcriptional forms was absent in both cell lines. This observation suggested the presence of mutations in the control region or the first exon of APC, or that mutation(s) could have affected the splicing efficiency or transcriptional initiation of the gene in these tumors. Furthermore, we found that the alternative splicing involving the 19 kDa protein of signal recognition particle (SRP19) gene, that is known to occur at exon 14 of APC, is also controlled in a tissue-specific manner, and one type of transcript lacked in some organs.
Hum Mol Genet 1993 Mar
PMID:Multiple forms of the APC gene transcripts and their tissue-specific expression. 838 66

The gene encoding the receptor for macrophage colony-stimulating factor 1 (CSF-1), the c-fms protooncogene, is selectively expressed in immature and mature mononuclear phagocytes and trophoblasts. Exon 1 is expressed only in trophoblasts. Isolation and sequencing of genomic DNA flanking exon 2 of the murine c-fms gene revealed a TATA-less promoter with significant homology to human c-fms. Reverse transcriptase primer extension analysis using exon 2 primers identified multiple clustered transcription initiation sites. Their position was confirmed by RNase protection. The same primer extension products were detected in equal abundance from macrophage or nonmacrophage sources of RNA. c-fms mRNA is acutely down-regulated in primary macrophages by CSF-1, bacterial lipopolysaccharide (LPS), and phorbol myristate acetate (PMA). Each of these agents reduced the abundance of c-fms RNA detectable by primer extension using an exon 3 primer without altering the abundance of presumptive short c-fms transcripts detected with exon 2 primers. Primer extension analysis with an intron 2 primer detected products at greater abundance in nonmacrophages. Templates detected with the intronic primer were induced in macrophages by LPS, PMA, and CSF-1, suggesting that each of the agents caused a shift from full-length c-fms mRNA production to production of unspliced, truncated transcripts. The c-fms promoter functioned constitutively in the RAW264 macrophage cell line, the B-cell line MOPC.31C, and several nonhematopoietic cell lines. Macrophage-specific expression and responsiveness to selective repression by LPS and PMA was achieved by the incorporation of intron 2 into the c-fms promoter-reporter construct. The results suggest that expression of the c-fms gene in macrophages is controlled by sequences in intron 2 that act by regulating transcription elongation.
Mol Cell Biol 1993 Jun
PMID:Expression of mRNA encoding the macrophage colony-stimulating factor receptor (c-fms) is controlled by a constitutive promoter and tissue-specific transcription elongation. 849 48

Transcription of a plasmid-located rrnB operon and the corresponding formation of ribosomes in vivo were studied using either T7 RNA polymerase or host RNA polymerase as transcriptase. The 23 S rRNA gene on the plasmid carried an A1067-->T mutation, which confers resistance against the drug thiostrepton. The proportion of particles containing plasmid-borne 23 S rRNA versus chromosome-borne rRNA was quantified with a precision of better than 10% by scanning sequence autoradiograms around nucleotide 1067. The activity of these particles was determined in the presence of thiostrepton which exclusively abolishes the activity of chromosomal wild-type ribosomes. When the plasmid rrnB operon was transcribed with phage T7 RNA polymerase, up to 80% of the rRNA synthesis was plasmid-directed (pulse labelling) in the late induction phase, most of which (about 85%) became degraded. The cells accumulated 50 S particles with plasmid-borne intact rRNA that was hardly found in 70 S ribosomes, i.e. particles harbouring plasmid-borne rRNA did not enter the pool of active ribosomes. The particles with plasmid-derived rRNAs were also practically inactive in protein synthesis in vitro. However, the rRNA was functional as shown by reconstitution analysis. The same patterns were found at various expression levels of the plasmid rrnB operon, indicating that not the overproduction of rRNA but rather the T7 transcriptase was responsible for the observed effects. However, when the plasmid rrnB operon was transcribed with host RNA polymerase, growth was not affected upon induction, the 30 S to 50 S to 70 S ratios in the cell were not altered, both 50 S subunits and 70 S ribosomes contained large amounts of plasmid-borne rRNA, and the particles with plasmid-derived rRNA were active in vitro. When the induction of rRNA transcription by T7 RNA polymerase was performed at 25 degrees C instead of 37 degrees C, an almost normal pattern was observed. Inactive 50 S particles did not accumulate, and large amounts of plasmid-borne rRNA were found in the pool of 70 S ribosomes. Lowering the induction temperature reduces the transcription rate by T7 RNA polymerase, which is five times faster at 37 degrees C than the host polymerase. The results suggest that the formation of active ribosomal subunits in vivo requires a fine adaptation of the transcription rate of rRNAs and the assembly process, underlining the importance of a coupling between rRNA transcription and ribosome assembly in vivo. T7 RNA polymerase cannot replace the host RNA polymerase in this process at 37 degrees C.
J Mol Biol 1993 Jun 05
PMID:Coupling of rRNA transcription and ribosomal assembly in vivo. Formation of active ribosomal subunits in Escherichia coli requires transcription of rRNA genes by host RNA polymerase which cannot be replaced by bacteriophage T7 RNA polymerase. 851 41

A cDNA library prepared from mRNA extracted from immature male gonads of the bivalve mollusc Ensis minor (razor shell) was probed with a 133-bp reverse-transcriptase PCR product corresponding to a segment of the sperm protein EM6 [Giancotti, V., Russo, E., Gasparini, M., Serrano, D., Del Piero, D., Thorne, A. W., Cary, P.D. & Crane-Robinson, C. (1993) Eur. J. Biochem. 136, 509-516]. A single 1.5-kb clone was found to encode both sperm proteins EM1 and EM6. Mass spectrometry was used to define the C-terminus of EM1, and since the N-terminus of EM6 is known from Edman degradation, this showed that the pentapeptide NTNNS must be lost on proteolytic processing. Both EM1 and EM6 contain highly repeated amino acid sequences, suggestive of extended structures. EM1 contains seven tandem repeats of the dipeptide S(K/R), followed by six potential cdc2 phosphorylation sites and seven repeats of the octapeptide KRSASKKR, with occasional K/R substitutions. EM6 contains a globular domain preceded by 17 almost identical uninterupted tandem repeats of the motif KKRSXSRKRSAS, where X is charged. Its C-terminus contains 15 short basic clusters. Assignment of EM1 and EM6 to the established categories of molluscan sperm proteins [PLI, PLII, PLIII, PLIV; Ausio, J. (1992) Mol. Cell. Biochem. 115, 163-172] is discussed.
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PMID:A precursor-product relationship in molluscan sperm proteins from Ensis minor. 852 37

The pleiotropic effects of the viable yellow mutation (Avy), an allele of the mouse agouti coat-color locus, include increased susceptibility to spontaneous and chemically induced tumors that affect a wide variety of tissues. As a first step toward understanding the molecular basis of this phenomenon, we established permanent fibroblast-like cell lines from newborn Avy/a and control congenic a/a mice and compared their growth characteristics in vitro. From the VY/WffC3Hf/Nctr and YS/WffCH3f/Nctr-Avy inbre strains, each of which carries the Avy allele on a congenic background, 38 clonal Avy/a and 16 clonal a/a lines were established. Regardless of inbred strain, all Avy/a cell lines exhibited a significant degree of spontaneous transformation, as assessed by focus formation in monolayer culture, whereas none of the a/a cell lines formed foci in prolonged cultures. To test whether changes in dosage of the Avy- or a-bearing chromosomes were related to these events, we analyzed each cell line with a closely linked molecular probe from the Emv-15 locus, which in the VY strain detects a restriction fragment length variant (RFLV) informative for the Avy- and a-bearing chromosomes. Most of the transformed foci maintained heterozygosity for RFLVs detected by the probe, but two of the transformants lost the a-associated RFLV, and at least one of the transformants exhibited amplification of the Avy-associated RFLV. When the transformants were analyzed with 5' sequences derived from the recently cloned agouti gene, three of eight transformants lost the a-associated RFLV, and two of the transformants showed amplification of the Avy-associated RFLV. Reverse transcriptase-polymerase chain reaction assays indicated that agouti RNA was detected in Avy/a, not a/a cell lines. Surprisingly, some of the Avy/a transformants lacked agouti RNA. These results suggest that deregulated expression of the Avy allele is required for the initiation but not for the maintenance of transformation of the Avy/a cell cultures. These cell lines may provide an in vitro culture system for studying the effect of the agouti gene on tumorigenicity as well as to potentially study other pleiotropic phenotypes.
Mol Carcinog 1996 Jan
PMID:Differential spontaneous transformation in vitro of newly established mouse fibroblast lines carrying or lacking the viable yellow mutation (Avy) of the mouse agouti locus. 856 69

Troponin T, which links the troponin complex to tropomyosin, is found as multiple isoforms in the hearts of many animal species. Changes in isoform composition have been correlated with variation in myofilament sensitivity to calcium. In order to determine the origin of diversity of the cardiac troponin T (cTnT) isoforms indicated by existing protein data, we have determined the sequences and patterns of expression of mRNAs encoding troponin T in fetal and adult heart and those present in adult heart in end-stage failure. Three main regions of alternative splicing within the cTnT coding region were identified using reverse-transcriptase polymerase chain reaction (RT-PCR). Alternatively spliced RNAs are developmentally regulated and some of the fetal forms are expressed in adult failing heart. The molecular structure of the spliced regions was determined from cloned cDNAs and RT-PCR products. In the 5' region of the mRNA, isoforms are generated by the inclusion or exclusion of 15-, 3- and 27-nucleotide (nt) sequences and by the inclusion or exclusion of a separate 3-nt sequence. In the 3' region of the mRNA, alternative splicing involves a 9-nt sequence which can be present in full, in part or not at all. A further splicing site was identified in the central region involving a 234-nt sequence and resulting in rare but detectable mRNAs. This work demonstrates the complexity of cTnT RNA composition in human heart and provides the information necessary to address the function of cTnT isoforms in contraction.
J Mol Cell Cardiol 1995 Oct
PMID:Molecular cloning of human cardiac troponin T isoforms: expression in developing and failing heart. 857 38

The genes for the long form of the human and the short form of the mouse PRL receptors were transfected independently into NIH 3T3 cells. Reverse transcriptase-polymerase chain reaction indicated that the transfectant designated LFH contained message for only the long form and the transfectant designated SFM had message for only the short form of the receptor. Both transfectant cell lines specifically bound lactogenic hormones with high affinity and responded to PRL in culture with a 2- to 3-fold increase in cell number preceded by transient activation of mitogen-activated protein kinase. After a PRL-responsive casein-chloramphenicol acetyl transferase (CAT) construct was introduced into both LFH and SFM cells, CAT activity was induced by PRL only in the LFH-CAT cells. Thus, while the long form of the receptor can transduce the differentiation signal, both the long and the short forms of the receptor can signal the cells to grow.
Mol Endocrinol 1995 Dec
PMID:Transduction of prolactin's (PRL) growth signal through both long and short forms of the PRL receptor. 861 11

To study regulation of the plastid-localized maize carotenoid biosynthetic pathway, a cDNA encoding phytoene desaturase (PDS) was isolated and characterized. The DNA sequence of the maize Pds cDNA was determined and compared with available dicot Pds genes. The deduced PDS protein, estimated at 64.1 kDa (unprocessed), had a dinucleotide binding domain and conserved regions characteristic of other carotene desaturases. Alignment of available PDS sequences from distantly related organisms suggests that Pds has potential as a phylogenetic tool. By use of heterologous complementation in Escherichia coli, maize PDS was shown to catalyze two desaturation steps converting phytoene to zeta-carotene. RFLP (restriction fragment length polymorphism) mapping was used to place Pds on chromosome 1S near viviparous5 (vp5), and RT-PCR (reverse-transcriptase polymerase chain reaction) analysis indicated reduced Pds transcript in vp5 mutant relative to normal endosperm. Other phytoene-accumulating mutant endosperms, vp2 and white3 (w3), showed no difference in Pds transcript accumulation as compared with normal endosperm counterparts. RT-PCR analysis of Pds transcript accumulation in developing endosperm showed Pds was constitutively expressed. Therefore, endosperm carotenogensis is not regulated by increasing the level of Pds transcripts.
Plant Mol Biol 1996 Jan
PMID:Cloning and characterization of a maize cDNA encoding phytoene desaturase, an enzyme of the carotenoid biosynthetic pathway. 861 51

We measured in rat aorta rings the relaxant activity of a number of peptides derived from the activating sequence (SLIGRL, or PP6) of the proteinase-activated receptor-2 (PAR-2). The relaxant action of PP6-NH2 mimicked the action of low concentrations of trypsin (0.5-1 unit/ml; 1-2 nM), was dependent on an intact endothelium, and was blocked by N-omega-nitro-L-arginine methyl ester but not by N-omega-nitro-D-arginine methyl ester. The relaxant actions of PP6, SLIGRL-NH2 (PP6-NH2), SLIGR (PP5), and SLIGR-NH2 (PP5-NH2) were comparable in magnitude, with relative potencies of PP6-NH2 > or = PP6 > PP5-NH2 > PP5. Peptides lacking either a leucine at position 2 (SAIGRL) or an arginine at position 5 (SLIGAL) exhibited markedly reduced or no relaxant activity; nevertheless, the tetrapeptide LIGR-NH2 exhibited low but detectable intrinsic activity. With the use of reverse-transcriptase/polymerase chain reaction, we documented the presence of PAR-2 mRNA in aorta tissue and determined that the rat aorta amino-terminal receptor-activating sequence was the same as that reported for the murine PAR-2 receptor. We concluded that the rat aorta tissue has a PAR-2 receptor that can be activated by peptides as short as four amino acids; the leucine and arginine at positions 2 and 5, respectively, of the proteolytically revealed PAR-2 receptor-activating sequence play key roles in regulating receptor function.
Mol Pharmacol 1996 Feb
PMID:Proteinase-activated receptor-2 in rat aorta: structural requirements for agonist activity of receptor-activating peptides. 863 54

Mouse neuroblastoma Neuro-2a cells were examined for the expression of pro-enkephalin mRNA, protein, and Met-enkephalin ([Met]-Enk) peptide. Reverse transcriptase/polymerase chain reaction (RT/PCR) and in situ hybridization demonstrated the presence of pro-enkephalin mRNA in these cells. Immunocytochemistry using an antibody which recognizes pro-enkephalin and high pressure liquid chromatography (HPLC) followed by radioimmunoassay indicated that pro-enkephalin was synthesized in these cells and processed to yield the bioactive pentapeptide, [Met]-Enk. Furthermore, release studies showed that the [Met]-Enk was secreted from these cells with high K+ stimulation. Using double labeling, in situ hybridization combined with immunocytochemistry, we demonstrated that prohormone convertase 2 (PC2) mRNA is colocalized with pro-enkephalin in the same Neuro-2a cells, suggesting that this enzyme may be responsible for processing this precursor. we also showed the presence of vasopressin mRNA and arginine-vasopressin peptide in these cells using in situ hybridization and immunocytochemistry, respectively. Thus, the Neuro-2a cells are a multiple neuropeptide-producing cell line and an excellent model for studying the mechanisms involved in the synthesis, intracellular targeting and processing of endogenous pro-enkephalin and pro-vasopressin, as well as other transfected neuropeptide precursors.
Mol Cell Endocrinol 1995 Sep 22
PMID:The Neuro-2a neuroblastoma cell line expresses [Met]-enkephalin and vasopressin mRNA and peptide. 867 23


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