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)

The neural cell adhesion molecule (N-CAM) is an important mediator of calcium independent cell-cell interactions. Variations in the primary structure of the protein are due to alternative splicing of pre-mRNA in the region encoding the extracellular, trans-membrane and cytoplasmic domains. In order to identify the patterns of exon usage during development of skeletal muscle and brain of the mouse, a coupled reverse-transcriptase/polymerase chain reaction was used to identify the murine homologues of the muscle-specific domain (MSD), located between exons 12 and 13 in human N-CAM mRNA. The cDNAs produced have been cloned and sequenced, or analysed directly. The amplification reactions were shown to maintain the concentration ratios of the initial cDNAs. The results indicate that the mouse homologue to exon MSD1a is under tissue and developmental regulation that is independent of exons MSD1b and MSD1c. The inclusion of the triplet exon AAG is also regulated in a cell- and stage-specific manner, which is independent of the other alternatively spliced exons of this domain.
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PMID:The muscle specific domain of mouse N-CAM: structure and alternative splicing patterns. 171 58

Amelogenins, a family of extracellular matrix proteins of the dental enamel, are transiently but abundantly expressed by ameloblasts during tooth development. Amelogenins seem to regulate the formation of crystallites during the secretory stage of enamel development, while they are specifically degraded during tooth-bud maturation. In this paper we report the characterization of the AMGX and AMGY genes on the short arms of the human X and Y chromosomes which encode the amelogenins. Our studies on the expression of the amelogenin genes in male developing tooth buds showed that both the AMGX and AMGY genes are transcriptionally active and encode potentially functional proteins. We have isolated genomic and cDNA clones from both the AMGX and AMGY loci and have studied the sequence organization of these two genes. Reverse transcriptase (RT)PCR amplification of the 5' portion of the amelogenin transcripts revealed several alternatively spliced products. The splicing pattern observed in the Y-derived mRNA varies from that of the X-derived mRNA. The promoter regions from both genes and the predicted amelogenin protein sequences are presented. This information will be useful for studying the molecular basis of X-linked amelogenesis imperfecta, for understanding the evolution and regulation of gene expression on the mammalian sex chromosomes, and for investigating the role of amelogenin genes during tooth development.
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PMID:The human enamel protein gene amelogenin is expressed from both the X and the Y chromosomes. 146 23

The alpha 2/delta subunit of voltage sensitive Ca2+ channels expressed in PC12 has been cloned and partially sequenced. The message observed in Northern blot analysis displays a 7.5 kb transcript, identical in size to mRNA of rabbit skeletal muscle and rat brain. The nucleotide sequence of the cloned alpha 2 subunit of the PC12 specific cDNA is > 99% identical to rat brain sequence and 85% to skeletal muscle. Reverse-transcriptase-polymerase chain reaction (RT-PCR) of the alternative splicing region identifies two deleted regions of 57 bp and 21 bp in PC12 expressed alpha 2/delta transcript. The alternative variant alpha 2e of alpha 2/delta subunit which is expressed in PC12 cells was previously identified in human embryonic kidney (HEK293) cells. RT-PCR analysis show two different sized alternative PCR fragments in rat lung and none in rat spleen, kidney and intestine. Antibodies prepared against a 19 amino acid peptide within the alternative spliced region effectively inhibits [3H]dopamine release in PC12 cells. This implies that the alternatively spliced region is positioned extracellularly and is involved in regulation of the L-type Ca2+ channel-mediated transmitter release.
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PMID:Identification of the alternative spliced form of the alpha 2/delta subunit of voltage sensitive Ca2+ channels expressed in PC12 cells. 747 72

Using immunostaining, immunoblot, reverse-transcriptase polymerase chain reaction and Southern blot, we found that expressions of CD44 isoforms and E-cadherin were very closely linked and were correlated with the differentiation status in human urothelial cell lines and clinical specimens of transitional cell carcinoma. Normal urothelium, well to moderately differentiated cell lines and surgical samples expressed E-cadherin and large CD44 isoforms containing exon v6, which was pivotal in metastasis of rat pancreatic cell line model. Poorly differentiated cell lines and surgical samples, were E-cadherin-negative and expressed primarily standard form CD44, which did not contain exon v6. We concluded that CD44v6 isoforms and E-cadherin were both down-regulated during the carcinogenesis of urothelium. The large exon v6 containing CD44 isoforms were readily detected in normal urothelium, therefore, were not likely linked to cancer metastasis. E-cadherin and CD44v6 may be used as differentiation markers for human urothelial tumors. Immunohistochemical study solely with antibody against epitopes encoded by exon v6 alone is not informative enough as other alternatively spliced exons may change the function of CD44v6 isoforms.
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PMID:Correlation of expression of CD44 isoforms and E-cadherin with differentiation in human urothelial cell lines and transitional cell carcinoma. 753 58

cDNA clones for calretinin, a member of the troponin-C family of calcium-binding proteins, were isolated from a cDNA library of the human colon carcinoma cell line WiDr. Sequence analysis revealed two forms of alternatively spliced calretinin mRNAs encoding C-terminally truncated proteins. Exon 7 was either spliced to exon 9 (delta 8) or to exon 10 (delta 8,9); both resulted in a frame shift and a translational stop at the second codon of exon 9 (delta 8), or at codon 15 of exon 10 (delta 8,9), respectively. The presence of delta 8 and delta 8,9 calretinin mRNA in WiDr cells was confirmed using reverse-transcriptase PCR and sequence analysis of the amplicon, as well as by a ribonuclease protection assay. Co115/3 and three other human colon carcinoma cell lines were found, by reverse-transcriptase PCR to also contain delta 8,9 calretinin mRNA. The truncated proteins were able to bind calcium, as evidenced by a calcium blot of the delta 8 form (calretinin-20k) and delta 8,9 form (calretinin-22k) expressed in Escherichia coli. Immunohistochemical staining using an antiserum specific for the novel C-terminus of calretinin-22k confirmed its presence in WiDr, Co115/3 and three additional colon carcinoma cell lines. The fact that alternative splicing of calretinin was found in five different cell lines suggests that alternatively spliced calretinins fulfill a physiological function.
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PMID:Alternative splicing of calretinin mRNA leads to different forms of calretinin. 760 11

Bovine herpesvirus 1 (BHV-1) establishes a latent infection in sensory ganglionic neurons of infected animals. Expression of latency-related (LR) gene products is controlled by a 980-bp fragment (LR promoter). DNA sequence analysis revealed that two major open reading frames (ORFs) are in the LR gene. Antibodies directed against both ORFs were generated in rabbits by using synthetic peptides. Antibody P2, which is directed to sequences near the amino terminus of ORF 2, recognized a 41-kDa protein in lytically infected cells, suggesting that ORF 2 encodes a protein. When the LR gene was inserted into a mammalian expression vector and subsequently transfected into COS-7 cells, a 41-kDa protein was detected by use of silver-stained sodium dodecyl sulfate-polyacrylamide gels and by the P2 antibody. In contrast, this protein was not detected in mock-transfected cells. Deletion of DNA sequences containing ORF 2 blocked synthesis of the 41-kDa protein in COS-7 cells. Reverse transcriptase-mediated PCRs indicated that splicing occurs near the C terminus of ORF 2. Further studies indicated that LR RNA was alternatively spliced in latently infected cattle and that a fraction of LR RNA was poly(A)+. Taken together, these studies suggested that a spliced LR transcript has the potential to encode a 41-kDa protein.
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PMID:Identification of gene products encoded by the latency-related gene of bovine herpesvirus 1. 763 78

The L-type voltage-dependent calcium channel (L-VDCC) is assumed to be a critical component of excitation-contraction coupling in smooth muscle. Using pregnant rat myometrium, we examined the hypothesis that parturition is associated with significant changes in the expression of the alpha 1 subunit of the L-VDCC at the mRNA or protein level. The binding of radiolabeled dihydropyridine, which correlates with the total number of calcium channels in the membrane, was increased by 14 days' gestation, in comparison to that in nonpregnant controls. The elevation in binding capacity persisted through labor and fell postpartum. Northern and RNA dot-blot analysis demonstrated the highest level of expression on Days 20 and 21, with a 3- to 10-fold decrease during parturition. We believe these studies are most consistent with a one-day lag time between mRNA and protein expression, and generally support a modest increase in L-VDCC expression in pregnancy and labor. Reverse transcriptase polymerase chain reaction was used to examine changes in isoform expression in Motif IV, a region of the alpha 1 subunit known to be alternatively spliced. These studies revealed the presence of multiple isoforms in rat myometrium, with a predominance of IVS3B. Interestingly, a marked increase in the ratio of S3B:S3A was noted at parturition. In summary, these data demonstrate that the number of L-type calcium channels, although increased in pregnancy, do not change prior to, or with the onset of, myometrial contraction. Intriguingly, mRNA expression was markedly decreased at parturition. The change in isoform expression during labor is of unknown, but potential, physiologic significance.
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PMID:Changes in the expression of the L-type voltage-dependent calcium channel during pregnancy and parturition in the rat. 784

Examination of cDNAs for the laminin-binding alpha 7 integrin subunit identified two different sequences (designated X1 and X2) coding for the variable region between the III and IV homology repeat domains near the putative ligand-binding site. Sequencing of a mouse alpha 7 genomic clone established that the X1 and X2 regions are derived by mutually exclusive alternative mRNA splicing. Reverse transcriptase-polymerase chain reaction analysis of alpha 7 mRNA indicated that the X1 and X2 isoforms were present in equal amounts in mouse skeletal myoblasts and adult heart. However, in adult skeletal muscle, the X2 variant was exclusively expressed. Amino acid sequence homologies in the III/IV segment suggest that alpha 3 and alpha 6 are also alternatively spliced at this site. We identified alternatively spliced exons in a human alpha 6 genomic clone that encode X1- and X2-like segments. Analysis of the alpha 7 cytoplasmic domain indicated that this region was also alternatively spliced and like alpha 3 and alpha 6 could exist as the A or B form. In mouse skeletal and cardiac muscle the B form of alpha 7 was strongly expressed. However, we identified alpha 7A in neonate and adult skeletal muscle but not in cardiac tissue. High levels of alpha 7A were detected in differentiating myotubes, but in proliferating myoblasts only the alpha 7B isoform was present. These results indicate that alternative splicing of alpha 7 mRNA is differentially regulated during development and generates variant integrin chains with structurally and presumably functionally unique ligand-binding and cytoplasmic domains.
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PMID:Alternative extracellular and cytoplasmic domains of the integrin alpha 7 subunit are differentially expressed during development. 825 14

In the rabbit heart, multiple isoforms of cardiac troponin T (cTnT1 through cTnT5, from largest in size to smallest), a protein essential for calcium-regulated myofibrillar ATPase activity, have been identified, and a correlation has been found between these isoforms and myofilament sensitivity to calcium. We have sought to establish the molecular basis of this diversity. Restriction-digest analysis of genomic DNA has indicated that the rabbit cTnT gene is a single-copy gene. cTnT cDNA clones were isolated from cDNA libraries, yielding a consensus sequence for the protein. Newborn rabbit heart cDNAs, obtained using the reverse-transcriptase polymerase chain reaction (RT-PCR), were amplified using primers derived from this cDNA. Three full-length cDNAs that differed by the inclusion or exclusion of three short nucleotide sequences within the cDNAs were obtained. Amplification in the 5' half of the cDNAs confirmed that multiple cTnT products arose because of the variable inclusion of an 18- and a 30-nt sequence. The 30-nt sequence has homology with previously described alternatively spliced exons in rat and chicken cTnT, whereas the 18-nt sequence has not been described previously. RT-PCR in the 3' half of the cDNAs confirmed an additional region of heterogeneity: the presence, in part or in full, or absence of a 9-nt region, which matches the alternatively spliced exon 12 described for rat cTnT. In vitro transcription and translation of four cDNA clones containing both the 18- and 30-nt sequences, the 30-nt sequence, the 18-nt sequence, or neither generated protein isoforms that comigrated with cTnT1, cTnT2, cTnT3, and cTnT4, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Molecular basis of cardiac troponin T isoform heterogeneity in rabbit heart. 826 93

The C57BL/6 mouse differs from the BALB/c mouse in that its ear and skin mast cells and its progenitor bone marrow-derived mast cells (mBMMCs) do not express mouse mast cell protease (mMCP) 7. We now report that, as detected by nuclear run-on analysis, the mMCP-7 gene is transcribed in C57BL/6 mBMMCs at a rate comparable to that in BALB/c mBMMCs. Reverse transcriptase-polymerase chain reaction analysis and sequencing of the product revealed that the ears of C57BL/6 mice contain small amounts of a mMCP-7 transcript that possesses a 98-base pair deletion. The deletion begins at a normally quiescent cryptic splice site (G416TGAG), 98 base pairs upstream of the normal exon 2/intron 2 splice site (G514TGAG), and introduces a premature stop codon in the alternatively spliced transcript. Thus, even if translated, the mature protein would consist of only 18 amino acids as compared to 245 amino acids in normal mMCP-7. Sequence analysis of the mMCP-7 gene in the C57BL/6 mouse revealed that the cryptic splice site is activated due to a G514-->A point mutation at the first nucleotide of the normal exon 2/intron 2 splice site. This is the first report of a mutation of a gene that encodes a mast cell secretory granule constituent that leads to its loss of expression. Moreover, the mMCP-7 gene is the first found in any species that sequentially has undergone a splice site mutation to cause retention of an intron and then a second splice site mutation to cause activation of a cryptic splice site.
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PMID:Natural disruption of the mouse mast cell protease 7 gene in the C57BL/6 mouse. 857 65


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