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 relative abundance of primary transcript and mature mRNA of the c-myc, calcyclin, S14 ribosomal protein, and rRNA genes was determined densitometrically after reverse transcriptase-polymerase chain reaction and Northern blotting analysis in resting and mitogen-stimulated lymphocytes, proliferating and terminally differentiated HL-60 cells, and leukemic blast cells. Transcription and processing of c-myc and rRNA gene transcripts increased proportionally after mitogen stimulation, whereas these processes were independent of cell cycling status in the case of the S14 gene. Normal lymphocytes showed an unexpectedly large amount of primary transcript of the calcyclin gene, whereas the corresponding mRNA was undetectable. The abundance of c-myc, calcyclin, and S14 mRNA in terminally differentiated HL-60 cells decreased sharply, compared to their proliferating counterparts. This decrease reflected post-transcriptional modulation, since the abundance of precursor remained essentially unchanged. After HL-60 differentiation, the 32S rRNA levels remained relatively high, whereas the 45S primary transcript almost disappeared. Leukemic blast cells displayed highly variable precursor/mRNA ratios of c-myc, calcyclin, and S14 genes but consistently high ratios of 32S to 45S RNA, suggesting that the cleavage rate of the 32S rRNA was sharply reduced in these cells, resulting in an accumulation of this molecule. These results suggest the importance of efficient processing of primary transcript to generate adequate functional mRNA, thus regulating gene expression. Furthermore, in terminally differentiated cells and leukemic blast cells a stabilization of the primary transcript without efficient processing can be observed. The role of the stabilization of the primary transcript in terminal differentiation is further supported by the results of run-off transcription, indicating a sharp decrease of c-myc and calcyclin transcription rate in retinoic acid/dimethyl sulfoxide-treated HL-60 cells.
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PMID:Abundance of the primary transcript and its processed product of growth-related genes in normal and leukemic cells during proliferation and differentiation. 172 70

Binary complexes between messenger RNA and E. coli ribosomes were examined. A ribosome-mRNA binary complex on T4 gene 32 mRNA withstood inhibition by antibodies against ribosomal protein S1. Anti-S1 blocks ternary complex formation, as measured by "extension inhibition" or "toeprinting" analysis, only when preincubated with ribosomes prior to mRNA addition and not when anti-S1 was added after preincubation of ribosomes and mRNA. The ribosome was directly localized in a binary complex on two translation initiation sites by toeprinting analysis. In the absence of tRNA the ribosome halted cDNA synthesis by reverse transcriptase close to the Shine and Dalgarno sequence. Binary complex formation was inhibited by an oligodeoxynucleotide competitor of the Shine and Dalgarno sequence.
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PMID:Detection of Escherichia coli ribosome binding at translation initiation sites in the absence of tRNA. 200 10

Yeast mRNA introns contain a conserved sequence, TACTAAC, required for splicing. We previously identified a putative splicing intermediate characterized by a stop to reverse transcriptase at the TACTAAC box of the wild-type rp51A (ribosomal protein 51A gene) intron. We now show that this stop is due to a branch and occurs at the identical nucleotide in the actin intron TACTAAC box. We show further that the putative intermediate contains a complete intron and the 3' exon, but is missing the 5' exon. This RNA is largely in the form of a lariat. The lariat and the other putative splicing intermediates detected (two forms, of different molecular weights, of the excised intron and the free 5' exon) are compatible with the view that the cut at the 5' junction and lariat formation are early steps in yeast mRNA splicing and that substantial similarities exist between yeast and mammalian mRNA splicing.
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PMID:In vivo characterization of yeast mRNA processing intermediates. 609 13

Several genes, including RPS4X (ribosomal protein subunit 4), ZFX (zinc finger on the X chromosome), and UBE1 (ubiquitin-activating enzyme), have been shown to be expressed from the inactive X chromosome of cultured human cells. By contrast, these genes are subject to X-chromosome inactivation in tissues from adult mice. We have now examined the inactivation status of these genes in cultured mouse cells to determine whether the differences in X-chromosome inactivation between species is due to an intrinsic difference between human and mouse X-chromosome genes or whether it is a function of gene reactivation in cell culture per se. The expression of three mouse X-chromosome genes, Rps4, Zfx, and Ube1 was examined by reverse transcriptase polymerase chain reaction (RT-PCR) in heterozygous cultured cells from a cross of a laboratory mouse by Mus spretus, which were selected to uniformly express the X chromosome from the laboratory mouse parent. No expression of the M. spretus alleles of these genes was observed in the cell line (Hobmski), which is consistent with the patterns of expression previously observed in mouse in vivo and indicates that these genes remain stably inactivated in an immortalized mouse cell line. By cytogenetic and RT-PCR analyses the Hobmski cell line was shown to retain a late-replicating X chromosome from M. spretus, which expressed the M. spretus allele of the X (inactive) specific transcript (Xist). The Hobmski cell line will be a useful resource for studying the features that maintain X-chromosome genes inactive.
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PMID:Maintenance of X inactivation of the Rps4, Zfx, and Ube1 genes in a mouse in vitro system. 768 8

Immunity to Brucella abortus crucially depends on antigen (Ag)-specific T-cell mediated activation of macrophages, which are the major effectors of cell-mediated killing of this organism. Ribosomal preparations have been used as vaccines against several pathogens, including B. abortus, conferring a high degree of protection. In the present study, we have examined the pattern of T-helper (Th) cell response from infected BALB/c mice after in vitro stimulation with recombinant (r) L7/L12 ribosomal protein or gamma-irradiated B. abortus. In addition to Ag-specific proliferation, CD4+ T cells were tested for interleukin-2 (IL-2), IL-4 and interferon-gamma (IFN-gamma) mRNA expression and secretion. Detection of cytokine transcripts and secreted cytokines was performed using reverse transcriptase (RT)-polymerase chain reaction (PCR) and specific ELISA assays. Primed CD4+ T cells proliferated to the recombinant protein or whole B. abortus. The functional cytokine profile of the proliferating cells was typical of a Th1 cell phenotype, as we detected transcripts for IL-2 and IFN-gamma but not IL-4. Among the cytokines analysed, only IFN-gamma produced in the Th cell culture supernatants was detected by ELISA when bacteria or recombinant protein were used. Thus, rL7/L12 ribosomal protein and gamma-irradiated B. abortus preferentially stimulated IFN-gamma-producing Th1 cells after in vitro stimulation. The results of this study provide for the first time an explanation of why ribosomal vaccines may protect against intracellular infections, and an experimental basis for identifying polypeptides from a pathogen which stimulates the desired cytokine profile and Th cell response crucial for the design of genetically engineered candidate vaccines.
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PMID:Recombinant L7/L12 ribosomal protein and gamma-irradiated Brucella abortus induce a T-helper 1 subset response from murine CD4+ T cells. 787 46

The 16S rRNAs of 15 species of actinomycetes belonging to the genera Actinokineospora and Saccharothrix and the family Pseudonocardiaceae, including Amycolatopsis, Amycolata, Pseudonocardia, Saccharomonospora, and Saccharopolyspora species, were sequenced by using reverse transcriptase. The sequences were analyzed along with the sequences of reference actinomycetes by using distance matrix and parsimony methods. The wall chemotype IV genus Actinokineospora was found to be closely related to species of the genus Saccharothrix which have chemotype III walls. Together, these two genera formed a clade which was closely related to members of the family Pseudonocardiaceae which have chemotype IV walls. However, the phylogenetic branching pattern did not unambiguously resolve whether the members of all three taxa should be placed in a single family. We suggest, therefore, that the genera Actinokineospora and Saccharothrix should remain outside the family Pseudonocardiaceae until additional sequence or phenotypic data are available to decide the issue. The sequences of species belonging to the genera Amycolata and Pseudonocardia were always recovered as a mixed group in phylogenetic trees, and we propose that these organisms should be classified in an emended genus Pseudonocardia. This proposal is strongly supported by previously published lipid, ribosomal protein, and ultrastructure data.
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PMID:A phylogenetic analysis of the family Pseudonocardiaceae and the genera Actinokineospora and Saccharothrix with 16S rRNA sequences and a proposal to combine the genera Amycolata and Pseudonocardia in an emended genus Pseudonocardia. 818 93

We describe here the complete sequence (58,507 bp) of the mitochondrial genome of the brown alga Pylaiella littoralis (Ectocarpales). This molecule displays an AT content of 62.0% and contains seventy-nine genes, most of them (73) encoded on one strand. They include the usual mitochondrial set of protist genes and a number of rarer genes. Among these, several ribosomal protein genes and the rn5 were identified. Twenty-four tRNA genes are present in this genome, insufficient to decode all genes. The other conspicuous features of this molecule are: a large (3018 nucleotides) in-frame insertion of unknown function in the cox2 gene; the presence of two different lineages of group II introns, including complete reverse transcriptase-like genes, one in the cox1 and the other in the rnl gene; the concomitant occurrence of a T7-like RNA polymerase and of several well-conserved alpha-proteobacterial-type promoters; and a small nad11 gene, coding for the first domain only of this NADH dehydrogenase subunit. Altogether, the mitochondrial genome of P. littoralis exhibits both alpha-proteobacterial characteristics and evidences of the independent integration of several exogenous DNA fragments.
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PMID:The complete sequence of a brown algal mitochondrial genome, the ectocarpale Pylaiella littoralis (L.) Kjellm. 1147 79

The hypothesis that vestiges of the ancestral RNA-dependent RNA polymerase involved in the replication of RNA genomes of Archean cells are present in the eubacterial RNA polymerase beta' subunit and its homologues is discussed. We show that in the DNA-dependent RNA polymerases from the three cellular lineages a very conserved sequence of eight amino acids also found in a small RNA-binding site previously described for the E. coli polynucleotide phosphorylase and the S1 ribosomal protein is present. The optimal conditions for the replicase activity of the avian myeloblastosis virus reverse transcriptase are presented. The evolutionary significance of the in vitro modifications of substrate and template specificities of RNA polymerases and reverse transcriptases is also discussed.
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PMID:The origin and early evolution of nucleic acid polymerases. 1153 40

In addition to being a component of the large ribosomal subunit, ribosomal protein L20 of Escherichia coli also acts as a translational repressor. L20 is synthesized from the IF3 operon that contains three cistrons coding for IF3, and ribosomal proteins L35 and L20. L20 directly represses the expression of the gene encoding L35 and the expression of its own gene by translational coupling. All of the cis-acting sequences required for repression by L20, called the operator, are found on an mRNA segment extending from the middle of the IF3 gene to the start of the L35 gene. L20-mediated repression requires a long-range base-pairing interaction between nucleotide residues within the IF3 gene and residues just upstream of the L35 gene. This interaction results in the formation of a pseudoknot. Here we show that L20 causes protection of nucleotide residues in two regions of the operator in vitro. The first region is the pseudoknot itself and the second lies in an irregular stem located upstream of the L35 gene. By primer extension analysis, we show that L20 specifically induces reverse transcriptase stops in both regions. Therefore, these two regions define two L20-binding sites in the operator. Using mutations and deletions of rpml'-'lacZ fusions, we show that both sites are essential for repression in vivo. However L20 can bind to each site independently in vitro. One site is similar to the L20-binding site on 23S rRNA. Here we propose that L20 recognizes its mRNA and its rRNA in similar way.
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PMID:Translational feedback regulation of the gene for L35 in Escherichia coli requires binding of ribosomal protein L20 to two sites in its leader mRNA: a possible case of ribosomal RNA-messenger RNA molecular mimicry. 1216 43

Escherichia coli responses to four inhibitors that interfere with translation were monitored at the transcriptional level. A DNA microarray method provided a comprehensive view of changes in mRNA levels after exposure to these agents. Real-time reverse transcriptase PCRanalysis served to verify observations made with microarrays, and a chromosomal grpE::lux operon fusion was employed to specifically monitor the heat shock response. 4-Azaleucine, a competitive inhibitor of leucyl-tRNA synthetase, surprisingly triggered the heat shock response. Administration of mupirocin, an inhibitor of isoleucyl-tRNA synthetase activity, resulted in changes reminiscent of the stringent response. Treatment with kasugamycin and puromycin (targeting ribosomal subunit association as well as its peptidyl-transferase activity) caused accumulation of mRNAs from ribosomal protein operons. Abundant biosynthetic transcripts were often significantly diminished after treatment with any of these agents. Exposure of a relA strain to mupirocin resulted in accumulation of ribosomal protein operon transcripts. However, the relA strain's response to the other inhibitors was quite similar to that of the wild-type strain.
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PMID:Interfering with different steps of protein synthesis explored by transcriptional profiling of Escherichia coli K-12. 1452 28


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