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At least 1,153 records · Page 64Linked to original sources
PubMed1996

Direct visualization of uridylate deletion in vitro suggests a mechanism for kinetoplastid RNA editing.

Deletion of uridylates from the 3'-most editing site of synthetic ATPase 6 pre-mRNA can be visualized directly by coincubation of a radiolabeled substrate RNA and a synthetic gRNA in 20S fractions of T.brucie mitochondrial lysates. Substrate RNA cleavage is gRNA directed and occurs 3' to the uridylates to be deleted. U residues appear to be sequentially removed from the 3' end of the 5' cleavage product prior to religation of the two pre-mRNA halves. gRNA/mRNA chimeric molecules are also produced. Time course experiments indicate that chimeras appear after cleavage intermediates and edited product. Furthermore, a mutant gRNA promotes formation of edited product but not detectable chimeras. Our results suggest a model for kinetoplastid RNA editing in which chimeric molecules are nonproductive end products of editing and not intermediates that serve as a repository for deleted U's.

Adenosine Triphosphatases↗
PubMed2003

Speciation in Chlamydia: genomewide phylogenetic analyses identified a reliable set of acquired genes.

Horizontal gene transfer (HGT), a process through which genomes acquire sequences from distantly related organisms, is believed to be a major source of genetic diversity in bacteria. A central question concerning the impact of HGT on bacterial genome evolution is the proportion of horizontally transferred sequences within genomes. This issue, however, remains unresolved because the various methods developed to detect potential HGT events identify different sets of genes. The present-day consensus is that phylogenetic analysis of individual genes is still the most objective and accurate approach for determining the occurrence and directionality of HGT. Here we present a genome-scale phylogenetic analysis of protein-encoding genes from five closely related Chlamydia, identifying a reliable set of sequences that have arisen via HGT since the divergence of the Chlamydia lineage. According to our knowledge, this is the first systematic phylogenetic inference-based attempt to establish a reliable set of acquired genes in a bacterial genome. Although Chlamydia are obligate intracellular parasites of higher eukaryotes, and thus suspected to be isolated from HGT more than the free-living species, our results show that their diversification has involved the introduction of foreign sequences into their genome. Furthermore, we also identified a complete set of genes that have undergone deletion, duplication, or rearrangement during this evolutionary period leading to the radiation of Chlamydia species. Our analysis may provide a deeper insight into how these medically important pathogens emerged and evolved from a common ancestor.

Base Composition↗
PubMed1994

RNA editing in mitochondria of cultured trypanosomatids: translatable mRNAs for NADH-dehydrogenase subunits are missing.

RNA editing in mitochondria of kinetoplastid protozoa involves the posttranscriptional insertion and deletion of uridylate residues in protein encoding regions of pre-mRNAs. Editing is required to remove gene-encoded translational defects or to convert a nonsense sequence into a sense message. In cultured trypanosomatids, however, translationally defective pre-mRNAs for a number of NADH-dehydrogenase subunits are not converted into functional mRNAs by editing. In this report, the available data are discussed in the context of current models for RNA editing.

Animals↗
PubMed1999

Agonist-directed signaling of serotonin 5-HT2C receptors: differences between serotonin and lysergic acid diethylamide (LSD).

For more than 40 years the hallucinogen lysergic acid diethylamide (LSD) has been known to modify serotonin neurotransmission. With the advent of molecular and cellular techniques, we are beginning to understand the complexity of LSD's actions at the serotonin 5-HT2 family of receptors. Here, we discuss evidence that signaling of LSD at 5-HT2C receptors differs from the endogenous agonist serotonin. In addition, RNA editing of the 5-HT2C receptor dramatically alters the ability of LSD to stimulate phosphatidylinositol signaling. These findings provide a unique opportunity to understand the mechanism(s) of partial agonism.

3T3 Cells↗
PubMed1995

Trypanosoma brucei mitochondrial guide RNA-mRNA chimera-forming activity cofractionates with an editing-domain-specific endonuclease and RNA ligase and is mimicked by heterologous nuclease and RNA ligase.

RNA editing in trypanosomes has been proposed to occur through transesterification or endonuclease cleavage and RNA ligation reactions. Both models involve a chimeric intermediate in which a guide RNA (gRNA) is joined through its 3' oligo(U) tail to an editing site of the corresponding mRNA. Velocity centrifugation of Trypanosoma brucei mitochondrial extracts had been reported to completely separate the gRNA-mRNA chimera-forming activity from endonuclease activity (V. W. Pollard, M. E. Harris, and S. L. Hajduk, EMBO J. 11:4429-4438, 1992), appearing to rule out the endonuclease-RNA ligase mechanism. However, we show that an editing-domain-specific endonuclease activity does cosediment with the chimera-forming activity, as does the RNA ligase activity, but detection of the specific endonuclease requires reducing assay conditions. This report further demonstrates that the T. brucei chimera-forming activity is mimicked by mung bean nuclease and T4 RNA ligase. Using cytochrome b (CYb) preedited mRNA and a model CYb gRNA, we found that these heterologous enzymes specifically generate CYb gRNA-mRNA chimeras analogous to those formed in the mitochondrial extract. These combined results provide support for the endonuclease-RNA ligase mechanism of chimera formation.

Animals↗
PubMed1994

Only cytidines 5' of the apolipoprotein B mRNA mooring sequence are edited.

A 22 nucleotide 'cassette' containing three distinct sequence elements is required for efficient apolipoprotein B (apoB) RNA editing. One of the elements, the mooring sequence, has been proposed as the apoB RNA-recognition element in binding 66 and 44 kDa proteins during editosome assembly. We show here that editing can only take place on cytidines 5' of the mooring sequence; thereby providing further proof for the proposed orientation-specific assembly of editing factors at the editing site. We also provide direct evidence for the existence of a cryptic mooring sequence immediately downstream of the wild-type editing site (between nucleotides 6688-6710). When a cytidine is introduced 5' of this site (at nucleotide 6687), editing occurs at wild-type (nucleotide 6666) and cryptic sites. The cytidine to be edited is not involved in 66 and 44 kDa protein binding, and therefore, the data suggest that the cryptic mooring sequence binds these factors, and may facilitate factor recruitment to the wild-type editing site. These data may also explain why wild-type levels of editing on chimeric, RNA editing substrates can only be achieved when the 22 nucleotide editing cassette is flanked 3' by apoB RNA sequence.

Apolipoproteins B↗
PubMed1993

RNA editing as a source of genetic variation.

Kinetoplastid RNA editing alters mitochondrial RNA transcripts by addition and deletion of uridine residues, producing open reading frames that may be twice as long as the original RNA. Although the COIII gene encoding cytochrome c oxidase subunit III in Trypanosoma brucei is edited along its entire length, the presumably homologous genes in two related trypanosomes, Leishmania tarentolae and Crithidia fasciculata, are only modestly edited at their 5' ends. We used a comparative approach to investigate the evolution of an edited gene and to determine how well editing creates conserved protein sequences. As RNA editing probably involves the pairing of several guide RNA molecules with the messenger RNA, we expected the edited proteins to be resistant to evolutionary change. Here we report that RNA editing is extensive in the mitochondria of four species of the insect parasite Herpetomonas, which is possibly an evolutionary precursor of T. brucei and L. tarentolae, and the discovery that RNA editing is a novel source of frameshift mutations over evolutionary time. The edited proteins accumulate mutations nearly twice as rapidly as the unedited versions.

Animals↗
PubMed1998

Apolipoprotein B RNA sequence 3' of the mooring sequence and cellular sources of auxiliary factors determine the location and extent of promiscuous editing.

Apolipoprotein B (apoB) RNA editing involves a cytidine to uridine transition at nucleotide 6666 (C6666) 5' of an essential cis -acting 11 nucleotide motif known as the mooring sequence. APOBEC-1 (apoB editing catalytic sub-unit 1) serves as the site-specific cytidine deaminase in the context of a multiprotein assembly, the editosome. Experimental over-expression of APOBEC-1 resulted in an increased proportion of apoB mRNAs edited at C6666, as well as editing of sites that would otherwise not be recognized (promiscuous editing). In the rat hepatoma McArdle cell line, these sites occurred predominantly 5' of the mooring sequence on either rat or human apoB mRNA expressed from transfected cDNA. In comparison, over-expression of APOBEC-1 in HepG2 (HepG2-APOBEC) human hepatoma cells, induced promiscuous editing primarily 5' of the mooring sequence, but sites 3' of the C6666 were also used more efficiently. The capacity for promiscuous editing was common to rat, rabbit and human sources of APOBEC-1. The data suggested that differences in the distribution of promiscuous editing sites and in the efficiency of their utilization may reflect cell-type-specific differences in auxiliary proteins. Deletion of the mooring sequence abolished editing at the wild type site and markedly reduced, but did not eliminate, promiscuous editing. In contrast, deletion of a pair of tandem UGAU motifs 3' of the mooring sequence in human apoB mRNA selectively reduced promiscuous editing, leaving the efficiency of editing at the wild type site essentially unaffected. ApoB RNA constructs and naturally occurring mRNAs such as NAT-1 (novel APOBEC-1 target-1) that lack this downstream element were not promiscuously edited in McArdle or HepG2 cells. These findings underscore the importance of RNA sequences and the cellular context of auxiliary factors in regulating editing site utilization.

APOBEC-1 Deaminase↗
PubMed2026

Genome agnostic, multi-level non-oncogene addiction-based systems pharmacology for rescuing metastatic relapsed/refractory neoplasias.

Rescue therapies for relapsed/refractory (r/r) metastatic neoplasias present significant unmet needs. Tumor tissue editing regimen for 13 r/r tumor types, carcinomas, sarcomas and hematologic neoplasias, included in 15 phase I/II trials, nuclear/cytokine receptor agonists, pioglitazone, plus/minus dexamethasone or all-trans retinoic acid or interferon-α to counterbalance tumor tissue homeostasis and reprogramming of cancer hallmarks, stress response inhibitors, COX-2 inhibitor, everolimus, lenalidomide, or clarithromycin, and a stress response inducer, low-dose metronomic chemotherapy with treosulfan, trofosfamide, capecitabine, or azacitidine. CR in three, cCR in another five r/r neoplasias, as the best response occurred after transcriptional reprogramming of cancer hallmarks, inflammation control or differentiation induction. Receptor agonist combinations for cCR induction can be identical among quite different tumor types and diversified within the same tumor histology. Data reveal ubiquitous, differential transcriptional access to non-oncogene addiction (NOA) networks that cope with cancer hallmarks/stress responses and three levels of therapeutic NOA targeting. (1) Agonists of nuclear/cytokine receptor NOAs critically target tumor identity and viability, while (2) transcriptional reprogramming of NOA networks that contribute to tumor tissue addiction, thereby genome-agnostically counteracting oncogene addictions. (3) Targeting edited NOAs may improve long-term outcome with CR/cCR (everolimus, IMiD). Transcriptionally accessible NOA targets offer high specificity, modest toxicity profile, low cost of therapy and outpatient treatment, independent of comorbidities. Adaptive targeting of the transcriptomic landscapes of tumor cell compartments breaks tumor tissue addiction and overcomes M-CRAC, post-therapy metastasis, cancer cell recolonization, acquired resistance and genetic heterogeneity. Thus, editing approaches provide a template for controlling metastatic r/r tumors. In the future, diagnostics of NOA networks and transcription factors involved in tumor tissue addiction may be as valuable for therapy selection as histological/molecular genetic tumor typing for the establishment of personalized hematology/oncology.

Hodgkin’s lymphoma↗
PubMed1997

Mitochondrial tRNAs in the lower fungus Spizellomyces punctatus: tRNA editing and UAG 'stop' codons recognized as leucine.

The mitochondrial DNA of the chytridiomycete fungus Spizellomyces punctatusen codes only eight tRNAs, although a minimal set of 24-25 tRNAs is normally found in fungi. One of these tRNAs has a CAU anticodon and is structurally related to leucine tRNAs, which would permit the translation of the UAG 'stop' codons that occur in most of its protein genes. The predicted structures of all S. punctatus tRNAs have the common feature of containing one to three mis-pairings in the first three positions of their acceptor stems. Such mis-pairing is expected to impair proper folding and processing of tRNAs from their precursors. Five of these eight RNAs were shown to be edited at the RNA level, in the 5'portion of the molecules. These changes include both pyrimidine to purine and A to G substitutions that restore normal pairing in the acceptor stem. Editing was not found at other positions of the tRNAs, or in the mitochondrial mRNAs of S. punctatus. While tRNA editing has not been observed in other fungi, the editing pattern inS.punctatus is virtually identical to that described in the amoeboid protozoan Acanthamoeba castellanii. If this type of mitochondrial tRNA editing has originated from their common ancestor, one has to assume that it was independently lost in plants, animals and in most fungi. Alternatively, editing might have evolved independently, or the genes coding for the components of the editing machinery were laterally transferred.

Amino Acid Sequence↗
PubMed2006

RNA editing complex interactions with a site for full-round U deletion in Trypanosoma brucei.

Trypanosome U insertion and U deletion RNA editing of mitochondrial pre-mRNAs is catalyzed by multisubunit editing complexes as directed by partially complementary guide RNAs. The basic enzymatic activities and protein composition of these high-molecular mass complexes have been under intense study, but their specific protein interactions with functional pre-mRNA/gRNA substrates remains unknown. We show that editing complexes purified through extensive ion-exchange chromatography and immunoprecipitation make specific cross-linking interactions with A6 pre-mRNA containing a single 32P and photoreactive 4-thioU at the scissile bond of a functional site for full-round U deletion. At least four direct protein-RNA contacts are detected at this site by cross-linking. All four interactions are stimulated by unpaired residues just 5' of the pre-mRNA/gRNA anchor duplex, but strongly inhibited by pairing of the editing site region. Furthermore, competition analysis with homologous and heterologous transcripts suggests preferential contacts of the editing complex with the mRNA/gRNA duplex substrate. This apparent structural selectivity suggests that the RNA-protein interactions we observe may be involved in recognition of editing sites and/or catalysis in assembled complexes.

Animals↗
PubMed2003

A Web-based screening instrument for depression and anxiety disorders in primary care.

BACKGROUND: Major depressive disorder (MDD) and anxiety disorders are common and result in considerable suffering and economic loss. People suffering from major depressive disorder and/or anxiety disorders are commonly encountered in the primary care setting. Unfortunately, most people with these disorders remain either untreated or inadequately treated; current data suggest that general practitioners fail to diagnose up to half of cases of major depressive disorder or anxiety. There is a need for screening tools that will help physicians and other professionals in primary care recognize and adequately treat major depressive disorder and anxiety disorders. While the currently-available self-report screening instruments have been demonstrated to be reliable and valid, there remain considerable barriers to their widespread use in primary care. OBJECTIVE: The purpose of the present study is to report preliminary validation data for a freely-available, brief, Web-based, self-report screener for major depressive disorder and anxiety disorders. METHODS: The Web-Based Depression and Anxiety Test (WB-DAT) was administered to 193 subjects who presented for assessment and/or treatment in ongoing research projects being conducted at the Mood and Anxiety Program and Clinical Research Department at the Centre for Addiction and Mental Health in Toronto, Ontario, Canada. Subjects completed the Web-based screening instrument and were subsequently interviewed with the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) Axis I Disorders (SCID-I/P). The diagnostic data from the screening instrument were then compared with the data from the individual's SCID-I/P interview. Diagnostic concordance between SCID-I/P diagnoses and the Web-Based Depression and Anxiety Test were assessed using Cohen's kappa, sensitivity, specificity, positive predictive value, negative predictive value, and efficiency. RESULTS: Agreement ranged from acceptable to good (0.57-0.70) for major depressive disorder, panic disorder with and without agoraphobia (PD+/-AG), social phobia/social anxiety disorder, obsessive compulsive disorder (OCD), generalized anxiety disorder (GAD), and post traumatic stress disorder (PTSD). With the exception of generalized anxiety disorder, the sensitivity (0.71-0.95) and specificity (0.87-0.97) for the major diagnostic categories assessed by the Web-Based Depression and Anxiety Test were good. The sensitivity for generalized anxiety disorder was somewhat lower (0.63) but acceptable. Positive predictive values were good (0.60-0.75) for major depressive disorder, obsessive compulsive disorder, generalized anxiety disorder, and post traumatic stress disorder, and acceptable for panic disorder with and without agoraphobia and for social phobia/social anxiety disorder. CONCLUSIONS: These preliminary data suggest that the Web-Based Depression and Anxiety Test is reliable for identifying patients with and without major depressive disorder and the anxiety disorders of panic disorder with and without agoraphobia, social phobia/social anxiety disorder, obsessive compulsive disorder, and post traumatic stress disorder. Further research is required in a larger sample in primary care.

Adolescent↗
PubMed1999

Editing of messenger RNA precursors and of tRNAs by adenosine to inosine conversion.

The double-stranded RNA-specific adenosine deaminases ADAR1 and ADAR2 convert adenosine (A) residues to inosine (I) in messenger RNA precursors (pre-mRNA). Their main physiological substrates are pre-mRNAs encoding subunits of ionotropic glutamate receptors or serotonin receptors in the brain. ADAR1 and ADAR2 have similar sequence features, including double-stranded RNA binding domains (dsRBDs) and a deaminase domain. The tRNA-specific adenosine deaminases Tad1p and Tad2p/Tad3p modify A 37 in tRNA-Ala1 of eukaryotes and the first nucleotide of the anticodon (A 34) of several bacterial and eukaryotic tRNAs, respectively. Tad1p is related to ADAR1 and ADAR2 throughout its sequence but lacks dsRBDs. Tad1p could be the ancestor of ADAR1 and ADAR2. The deaminase domains of ADAR1, ADAR2 and Tad1p are very similar and resemble the active site domains of cytosine/cytidine deaminases.

Adenosine↗
PubMed1996

Universality of mitochondrial RNA editing in cytochrome-c oxidase subunit I (coxI) among the land plants.

Plant mitochondrial pre-mRNAs often undergo C-to-U conversions, a phenomenon termed RNA editing. The molecular source of specificity and phylogenetic depth of the editing machinery remain to be determined. We amplified coxI gene fragments via the polymerase chain reaction from a diversity of taxa within the land plants, and sequenced each. Alignment and comparison of 25 homologous coxI gene sequences with those from plant species having known RNA editing sites which restore amino acid sequence consensus was used to infer sites of C-to-U conversions. Our results, derived using the comparative approach, imply that the plant mitochondrial editing machinery extends throughout vascular plant phylogeny, and also that this phenomenon is present in every major branch of the (non-vascular) Bryophyta: liverworts (Hepaticae), hornworts (Anthocerotae), and mosses (Musci). These results have important consequences for our thoughts on the evolutionary history of the plant RNA editing process, as they imply that editing is older than was previously believed.

Amino Acid Sequence↗
PubMed1999

Editing of glutamate receptor subunit B pre-mRNA by splice-site variants of interferon-inducible double-stranded RNA-specific adenosine deaminase ADAR1.

The interferon-inducible RNA-specific adenosine deaminase (ADAR1) is an RNA-editing enzyme that catalyzes the deamination of adenosine in double-stranded RNA structures. Three alternative splice-site variants of ADAR1 (ADAR1-a, -b, and -c) occur that possess functionally distinct double-stranded RNA-binding motifs as measured with synthetic double-stranded RNA substrates. The pre-mRNA transcript encoding the B subunit of glutamate receptor (GluR-B) has two functionally important editing sites (Q/R and R/G sites) that undergo selective A-to-I conversions. We have examined the ability of the three ADAR1 splice-site variants to catalyze the editing of GluR-B pre-mRNA at the Q/R and R/G sites as well as an intron hotspot (+60) of unknown function. Measurement of GluR-B pre-mRNA editing in vitro revealed different site-specific deamination catalyzed by the three ADAR1 variants. The ADAR1-a, -b, and -c splice variants all efficiently edited the R/G site and the intron +60 hotspot but exhibited little editing activity at the Q/R site. ADAR1-b and -c showed higher editing activity than ADAR1-a for the R/G site, whereas the intron +60 site was edited with comparable efficiency by all three ADAR1 splice variants. Mutational analysis revealed that the functional importance of each of the three RNA-binding motifs of ADAR1 varied with the specific target editing site in GluR-B RNA. Quantitative reverse transcription-polymerase chain reaction analyses of GluR-B RNA from dissected regions of rat brain showed significant expression and editing at the R/G site in all brain regions examined except the choroid plexus. The relative levels of the alternatively spliced flip and flop isoforms of GluR-B RNA varied among the choroid plexus, cortex, hippocampus, olfactory bulb, and striatum, but in all regions of rat brain the editing of the flip isoform was greater than that of the flop isoform.

Adenosine Deaminase↗
PubMed1991

Trans splicing integrates an exon of 22 nucleotides into the nad5 mRNA in higher plant mitochondria.

The genes coding for NADH dehydrogenase subunit 5 (nad5) in mitochondria of the higher plants Oenothera and Arabidopsis are split into five exons that are located in three distant genomic regions. These encode exons a + b, c and d + e, respectively. Maturation of the mRNAs requires two trans splicing events to integrate exon c of only 22 nucleotides. Both trans splicing reactions involve mitochondrial group II intron sequences that allow base pairings in the interrupted domain IV, demonstrating the flexibility of intron structures. The observation of fragmented intron sequences in plant mitochondria suggests that trans splicing is more widespread than previously assumed. RNA editing by C to U alterations in both Oenothera and Arabidopsis open reading frames improves the evolutionary conservation of the encoded polypeptides. Three C to U RNA editing events were observed in intron sequences.

Amino Acid Sequence↗
PubMedDate not supplied

An integrated software suite for surface-based analyses of cerebral cortex.

The authors describe and illustrate an integrated trio of software programs for carrying out surface-based analyses of cerebral cortex. The first component of this trio, SureFit (Surface Reconstruction by Filtering and Intensity Transformations), is used primarily for cortical segmentation, volume visualization, surface generation, and the mapping of functional neuroimaging data onto surfaces. The second component, Caret (Computerized Anatomical Reconstruction and Editing Tool Kit), provides a wide range of surface visualization and analysis options as well as capabilities for surface flattening, surface-based deformation, and other surface manipulations. The third component, SuMS (Surface Management System), is a database and associated user interface for surface-related data. It provides for efficient insertion, searching, and extraction of surface and volume data from the database.

Anatomy, Artistic↗