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)

An alternatively spliced transcript of the human insulin-like growth factor-I (IGF-I) gene is described. The transcript was identified in human liver RNA by reverse transcriptase-polymerase chain reaction, cloning, and sequencing. It contained IGF-I exons 3 and 4, 49 basepairs of exon 5, then exon 6 (exon 4-5-6). The 5'-donor site at the exon 5-6 junction was a cryptic 5'-donor splice site (IGF633). The 3'-acceptor site of the splice was the usual intron-exon 6 junction. A second pair of primers across the exon 5-exon 6 junction was used to confirm the presence of the transcript by reverse transcriptase-polymerase chain reaction. Cloning and sequencing this second fragment confirmed the presence of this splice in human liver. The exon 4-5-6 transcript was quantified at about 10% relative to the exon 4-6 transcript in human livers (n = 7 subjects), but was not detected in other tissues. The exon 4-5-6 transcript was found in cultured human hepatoma HepG2 cells and increased, relative to exon 4-6 transcripts, in response to GH, but not in cultured human lymphoblast IM-9 cells. The exon 4-5-6 splice predicts a prepro-IGF-I of 158 amino acid residues, with an E-peptide sequence of 24 residues (Ec). The deduced Ec peptide sequence is 73% homologous to the rat Eb-peptide sequence. The predicted final residues of the Ec peptide are frameshifted exon 6 codons ending in an in-frame stop codon. The predicted peptide sequences of Ec and Eb differ at the cleavage site of the Eb-peptide fragment (IBE1), which has been shown to have mitogenic activity. These data suggest that 1) the exon 4-5-6 splice has hepatic tissue expression and occurs by the use of a cryptic 5'-donor consensus splice site (IGF633) in exon 5; 2) exon 4-5-6 can be hormonally regulated in cultured human HepG2 cells; 3) exon 4-5-6 is the human counterpart of the rat IGF-IEb, because the complementary DNA and predicted sequences are homologous; and 4) the production of IBE1 is potentially regulated by alternative splicing.
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PMID:An alternatively spliced human insulin-like growth factor-I transcript with hepatic tissue expression that diverts away from the mitogenic IBE1 peptide. 772 Jun 41

Plasma membrane calcium pumps (PMCAs) play a major role in the maintenance and fine regulation of the intracellular Ca2+ concentration. Fourteen subregions of the normal human brain were carefully dissected and analyzed by reverse transcriptase-polymerase chain reaction for the distribution of mRNAs corresponding to the four known PMCA genes as well as their alternative splicing products at two previously defined 'hotspots' A and C. All PMCA genes were found to be expressed in every brain subregion; however, consistent differences were found in the distribution of alternative splice options. The four cortical regions and hippocampus were characterized by the relative preference of variants that include an entire exon at site C and lead to the expression of isoforms of the a-type. Inferior olive and olfactory bulb showed a relative preponderance of the b-form 'default' types of alternative splicing at site C, and a decrease or even the lack of 'differentiated' forms such as variants 1a and 1c. At the N-terminal splice site A, the default x-type variants were predominant in all brain regions for PMCA 1, 3, and 4. By contrast, the pattern of PMCA2 variants was the most variable, ranging from the presence of the entire set of 2x, 2w, and 2z forms in inferior olive to the almost exclusive presence of form 2z (excluding all alternatively spliced sequences) in the four cortical regions, caudate, and hippocampus. Regional differences in the PMCA splice type distribution in normal human brain may correlate with different demands on the regulation of the set-point resting Ca2+ levels in these areas. Changes in these patterns may correlate with altered physiological states of the affected regions and/or reflect an (early) sign of Ca2+ dyshomeostasis characteristic of many neurodegenerative diseases.
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PMID:Transcript distribution of plasma membrane Ca2+ pump isoforms and splice variants in the human brain. 772 25

Brush border myosin-I, or BBMI, constitutes the lateral links that connect in intestinal microvilli the core bundle of actin filaments to the membrane. Although related molecules have been identified in other higher eukaryotic tissues, northern blot analysis has indicated that the distribution of this particular myosin-I isoform is restricted essentially to intestine. Using reverse transcriptase polymerase chain reaction we have identified BBMI in a wide range of tissues including liver and testis. Our results also indicate that in testis the BBMI gene might be alternatively spliced.
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PMID:Identification of brush border myosin-I in liver and testis. 777 4

The chromosomal breakpoint and fusion transcripts of the pre-B-leukaemia-derived SEM cell line carrying a reciprocal t(4;11)(q21;q23) translocation were analysed. The breakpoint from derivative chromosome der4 was cloned and sequenced. The crossover site was localized in intron 7 of the ALL-1 gene on chromosome 11q23 and in a large intron of the AF-4 (FEL) gene. RNA transcripts from both wild-type genes and both hybrid genes were detected by reverse transcriptase polymerase chain reaction (RT-PCR) assays. In addition, alternatively spliced mRNA species derived from the der4 chromosome were found. They were generated by using the exon 5' of the breakpoint on der4 as a common splice donor site and the 5' boundaries of exons 8 or 9 of the ALL-1 gene as alternative splice acceptor sites. The hypothesis is proposed that selective pressure operators to maintain the presence of both derivative chromosomes as important elements in the leukaemogenic process.
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PMID:Molecular analysis of the chromosomal breakpoint and fusion transcripts in the acute lymphoblastic SEM cell line with chromosomal translocation t(4;11). 779 49

Analysis of TCR-beta gene recombination and expression was performed by quantitative PCR amplification technique throughout chicken embryogenesis and development. Our data demonstrated that TCR V beta 1 promoters were turned on by day 10 of embryogenesis, 2 days before detection of TCR-beta gene recombination. The V to D recombination step was first detected by day 11 of embryogenesis whereas DJ and V(D)J rearranged genes were detected 1 day later, on day 12 of embryogenesis. Thus, transcription of unrearranged TCR-beta genes in chickens precedes the expression of V(D)J recombinase activity as in mammals. In contrast, although TCR-beta rearrangement starts with the D to J recombination step in mammals, it can start either by the VD or the DJ step in chickens. Furthermore, reverse transcriptase-PCR amplification of TCR-beta transcripts revealed the presence of two kinds of alternative transcripts. These novel alternatively spliced products appeared in thymocytes from embryonic thymus during colonization periods and were absent in transformed T cell lines. Splicing sites are located in the middle of V beta 1 segments and lead to delta V beta 1-C beta and delta V beta 1-D beta-J beta-C beta transcripts. delta V beta 1-C beta transcripts might lead to synthesis of invariant truncated TCR beta-chains containing the aminoterminal portion of the V beta 1 region followed by the C beta region. Because this type of splicing can be generated by using all known V beta 1 members, these invariant forms could play a role in thymocyte development.
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PMID:Ontogeny of TCR V beta 1 expression revealed novel invariant alternative transcripts. 782 94

Previous studies have demonstrated proliferation of basement membranes in the optic nerve head in primary open angle glaucoma (POAG). We used in situ hybridization (ISH) of a radiolabeled riboprobe specific for human collagen IV, a ubiquitous component of basement membranes, to identify cells actively synthesizing basement membranes in the optic nerve head in POAG. In addition, to detect and further characterize the collagen IV mRNA transcripts, we used reverse transcriptase-polymerase chain reaction (RT-PCR) in total RNA extracted from individual optic nerve heads with POAG and from age-matched normal controls. ISH results demonstrate that, in POAG, numerous astrocytes in the prelaminar region expressed collagen IV mRNA. Lamina cribrosa cells and astrocytes in the compressed lamina cribrosa hybridized the probe. Few astrocytes and lamina cribrosa cells hybridized the probe in the optic nerve head of normal age-matched controls. RT-PCR products for collagen IV and for glyceraldehyde-3-dehydrogenase (G3PDH), a reference gene, were detected by agarose electrophoresis as single bands of the expected sizes and positively identified by Southern hybridization using specific cDNA probes in normal and POAG samples. No additional products (bands) were observed in RT-PCR experiments, indicating that there was no genomic DNA contamination in the total RNA extract. The lack of additional bands suggests that, at least in the ten samples used in this study, there were no alternatively spliced RNA products in any of the amplified sequences. Semi-quantitative analyses using densitometry showed a two-fold increase in collagen type IV PCR present in POAG samples. No differences were detected in levels of G3PDH PCR products between POAG and normal samples. This investigation provides evidence of increased biosynthesis of collagen type IV at the mRNA level in optic nerve heads with POAG. Whether this phenomenon represents a response to elevated intraocular pressure or a reparative mechanism to the loss of axons remains to be determined.
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PMID:Collagen type IV gene expression in human optic nerve heads with primary open angle glaucoma. 783 97

The ovine insulin-like growth factor-II (oIGF-II) gene is comprised of 9 exons that span approximately 25 kb. Approximately 750 nucleotides upstream of oIGF-II exon 1 are the three exons of the ovine insulin gene that are transcribed in the same direction as oIGF-II. The genomic organization and expression of the oIGF-II gene is similar to that of the human IGF-II gene. Four putative promoters direct the transcription of six 5' noncoding exons (1, 3, 4, 5, 6, and 7), which are alternatively spliced to the shared exons 8, 9, and 10. An ovine exon comparable to human exon 2 has not been identified. Multiple transcription initiation sites were identified for exons 1 and 6 by primer extension analysis. Using a reverse transcriptase polymerase chain reaction (RT-PCR) assay, exon 1 and 3 transcripts were shown to be expressed in adult but not fetal liver. In addition, a novel transcript, which contained exon 1 spliced directly to exon 8, was detected in adult liver. Exon 4 transcripts were not detected in either fetal or adult liver, whereas exon 6 and 7 transcripts were detected in both fetal and adult liver. Exon 5 transcripts were also expressed in both fetal and adult liver, which is in contrast to the tumor cell-specific expression of human exon 5. Like the human and rodent genes, the regulation of expression of the oIGF-II gene is under complex control.
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PMID:Characterization of the linked ovine insulin and insulin-like growth factor-II genes. 801 Nov 64

In RNA from human IgE-producing lymphocytes, we previously discovered two alternatively spliced epsilon-immunoglobulin mRNA isoforms that encode a novel secreted form of IgE and a membrane-bound species. Further analysis using epsilon-specific reverse transcriptase polymerase chain reactions has elucidated several additional alternatively spliced species of epsilon mRNA. One RNA isoform is generated by splicing the CH4 exon to a novel distal splice acceptor site, forming an epsilon RNA species (designated CH4-M2") that encodes a secreted epsilon protein 6 amino acids larger than the classic secreted epsilon protein. The other three novel epsilon RNAs are generated by splicing from within CH4 to a new exon structure (designated CH5) that is located between CH4 and the membrane exons. Since the three new mRNAs using CH5 share the same stop codon in CH5, they all encode the same novel protein, which is 10 amino acids shorter than the classic secreted epsilon heavy chain. The new alternatively spliced epsilon mRNAs reported here, in addition to the previously reported forms encoding membrane and larger secreted IgE, appear to reflect the normal splicing pattern in humans, as we have detected all these epsilon RNAs in all the human IgE-secreting cells and cell lines tested.
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PMID:Complex alternative RNA splicing of epsilon-immunoglobulin transcripts produces mRNAs encoding four potential secreted protein isoforms. 798 77

The cDNA for Endothelin-2 (ET-2) has been previously cloned and characterised; however, ET-2 remains the least studied of the endothelin isopeptides and little is known of its function and location. In the present study reverse transcriptase-polymerase chain reaction revealed the presence of seven alternatively spliced mRNA variants encoding ET-2, with a specific pattern of distribution in various human tissues. Computer alignment and analysis of the DNA sequences demonstrated alternative splicing of five exons of 52, 169, 123, 99 and 174 base pairs, in the carboxy terminal region of the mRNA encoding preproET-2. This region contains sites for the post-transcriptional processing of preproET-2 into mature ET-2, therefore we postulate that post-transcriptional processing may be disrupted or altered in these variants.
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PMID:Alternatively spliced mRNAs for human endothelin-2 and their tissue distribution. 832 58

Polymerase chain reaction [PCR, reverse transcriptase-PCR (RT-PCR)] has been used to amplify the mRNA subspecies of the plasma membrane calcium pump isoform 1 (PMCA1) in total RNA extracted from hamster tissues. Two primers were synthesized that encompass the site at which a 154-bp exon is included totally (PMCA1a), partially (PMCA1c and d), or completely excluded (PMCA1b) in the carboxy-terminal regulatory region. PCR amplification revealed two bands (PMCA1b and 1c) that are more abundant in various tissues, while Southern hybridization of the samples after PCR amplification has detected two additional mRNA variants corresponding to PMCA1a and 1d. The distribution of these mRNA variants are tissue specific and correlate well with the pump protein distribution patterns on immunoblot. Since these multiple bands on the immunoblot are not derived from proteolysis, it is suggested that they represent the PMCA1 isozymes encoded by these alternatively spliced mRNAs. To our knowledge, this is the first report to show all four alternatively spliced mRNAs that are simultaneously detected in one single RNA sample using PCR technique. Since these isozymes are different in their regulatory domain, their tissue-specific expression may be physiologically important.
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PMID:Use of the polymerase chain reaction for the detection of alternatively spliced mRNAs of plasma membrane calcium pump. 839 Aug 40


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