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Spliceosome

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https://www.readbyqxmd.com/read/28530653/structure-of-a-pre-catalytic-spliceosome
#1
Clemens Plaschka, Pei-Chun Lin, Kiyoshi Nagai
Intron removal requires assembly of the spliceosome on pre-mRNA and extensive remodelling to form the spliceosome's catalytic centre. Here we report the cryo-electron microscopy structure of the yeast pre-catalytic B complex spliceosome at near-atomic resolution. The mobile U2 snRNP associates with U4/U6.U5 tri-snRNP through U2/U6 helix II and an interface between U4/U6 di-snRNP and the U2 snRNP SF3b-containing domain, which also transiently contacts the helicase Brr2. The U2 snRNP 3' region is flexibly attached to the SF3b-containing domain and protrudes over the concave surface of tri-snRNP, where the U1 snRNP may reside before its release from the pre-mRNA 5'-splice site...
May 22, 2017: Nature
https://www.readbyqxmd.com/read/28529063/methodologies-for-studying-the-spliceosome-s-rna-dynamics-with-single-molecule-fret
#2
REVIEW
Clarisse van der Feltz, Aaron A Hoskins
The spliceosome is an extraordinarily dynamic molecular machine in which significant changes in composition as well as protein and RNA conformation are required for carrying out pre-mRNA splicing. Single-molecule fluorescence resonance energy transfer (smFRET) can be used to elucidate these dynamics both in well-characterized model systems and in entire spliceosomes. These types of single-molecule data provide novel information about spliceosome components and can be used to identify sub-populations of molecules with unique behaviors...
May 18, 2017: Methods: a Companion to Methods in Enzymology
https://www.readbyqxmd.com/read/28525753/the-u6-snrna-m-6-a-methyltransferase-mettl16-regulates-sam-synthetase-intron-retention
#3
Kathryn E Pendleton, Beibei Chen, Kuanqing Liu, Olga V Hunter, Yang Xie, Benjamin P Tu, Nicholas K Conrad
Maintenance of proper levels of the methyl donor S-adenosylmethionine (SAM) is critical for a wide variety of biological processes. We demonstrate that the N(6)-adenosine methyltransferase METTL16 regulates expression of human MAT2A, which encodes the SAM synthetase expressed in most cells. Upon SAM depletion by methionine starvation, cells induce MAT2A expression by enhanced splicing of a retained intron. Induction requires METTL16 and its methylation substrate, a vertebrate conserved hairpin (hp1) in the MAT2A 3' UTR...
May 18, 2017: Cell
https://www.readbyqxmd.com/read/28520720/identification-of-human-short-introns
#4
Emmanuel L Abebrese, Syed H Ali, Zachary R Arnold, Victoria M Andrews, Katharine Armstrong, Lindsay Burns, Hannah R Crowder, R Thomas Day, Daniel G Hsu, Katherine Jarrell, Grace Lee, Yi Luo, Daphine Mugayo, Zain Raza, Kyle Friend
Canonical pre-mRNA splicing requires snRNPs and associated splicing factors to excise conserved intronic sequences, with a minimum intron length required for efficient splicing. Non-canonical splicing-intron excision without the spliceosome-has been documented; most notably, some tRNAs and the XBP1 mRNA contain short introns that are not removed by the spliceosome. There have been some efforts to identify additional short introns, but little is known about how many short introns are processed from mRNAs. Here, we report an approach to identify RNA short introns from RNA-Seq data, discriminating against small genomic deletions...
2017: PloS One
https://www.readbyqxmd.com/read/28515276/assembly-of-the-u5-snrnp-component-prpf8-is-controlled-by-the-hsp90-r2tp-chaperones
#5
Anna Malinová, Zuzana Cvačková, Daniel Matějů, Zuzana Hořejší, Claire Abéza, Franck Vandermoere, Edouard Bertrand, David Staněk, Céline Verheggen
Splicing is catalyzed by the spliceosome, a complex of five major small nuclear ribonucleoprotein particles (snRNPs). The pre-mRNA splicing factor PRPF8 is a crucial component of the U5 snRNP, and together with EFTUD2 and SNRNP200, it forms a central module of the spliceosome. Using quantitative proteomics, we identified assembly intermediates containing PRPF8, EFTUD2, and SNRNP200 in association with the HSP90/R2TP complex, its ZNHIT2 cofactor, and additional proteins. HSP90 and R2TP bind unassembled U5 proteins in the cytoplasm, stabilize them, and promote the formation of the U5 snRNP...
May 17, 2017: Journal of Cell Biology
https://www.readbyqxmd.com/read/28504693/cyclin-dependent-kinase-7-is-a-therapeutic-target-in-high-grade-glioma
#6
S A Greenall, Y C Lim, C B Mitchell, K S Ensbey, B W Stringer, A L Wilding, G M O'Neill, K L McDonald, D J Gough, B W Day, T G Johns
High-grade glioma (HGG) is an incurable brain cancer. The transcriptomes of cells within HGG tumors are highly heterogeneous. This renders the tumors unresponsive or able to adapt to therapeutics targeted at single pathways, thereby causing treatment failure. To overcome this, we focused on cyclin-dependent kinase 7 (CDK7), a ubiquitously expressed molecule involved in two major drivers of HGG pathogenesis: cell cycle progression and RNA polymerase-II-based transcription. We tested the activity of THZ1, an irreversible CDK7 inhibitor, on patient-derived primary HGG cell lines and ex vivo HGG patient tissue slices, using proliferation assays, microarray analysis, high-resolution respirometry, cell cycle analysis and in vivo tumor orthografts...
May 15, 2017: Oncogenesis
https://www.readbyqxmd.com/read/28502770/an-atomic-structure-of-the-human-spliceosome
#7
Xiaofeng Zhang, Chuangye Yan, Jing Hang, Lorenzo I Finci, Jianlin Lei, Yigong Shi
Mechanistic understanding of pre-mRNA splicing requires detailed structural information on various states of the spliceosome. Here we report the cryo electron microscopy (cryo-EM) structure of the human spliceosome just before exon ligation (the C(∗) complex) at an average resolution of 3.76 Å. The splicing factor Prp17 stabilizes the active site conformation. The step II factor Slu7 adopts an extended conformation, binds Prp8 and Cwc22, and is poised for selection of the 3'-splice site. Remarkably, the intron lariat traverses through a positively charged central channel of RBM22; this unusual organization suggests mechanisms of intron recruitment, confinement, and release...
May 18, 2017: Cell
https://www.readbyqxmd.com/read/28501461/spliceosome-associated-factor-ctnnbl1-promotes-proliferation-and-invasion-in-ovarian-cancer
#8
Yingwei Li, Haiyang Guo, Chengjuan Jin, Chunping Qiu, Min Gao, Lei Zhang, Zhaojian Liu, Beihua Kong
Ovarian cancer is the most lethal gynecologic malignancy and the molecular pathogenesis of high-grade serous ovarian carcinoma has not been completely characterized. Numerous studies have shown that altered splicing patterns and splicing factors were found to contribute to tumor development and progression. In this study, we demonstrated that spliceosome-associated factor CTNNBL1 was significantly upregulated in high-grade serous ovarian carcinoma, the elevated level of CTNNBL1 indicates poor prognosis in patients with high-grade serous ovarian carcinoma...
May 10, 2017: Experimental Cell Research
https://www.readbyqxmd.com/read/28500052/exploring-the-impact-of-cleavage-and-polyadenylation-factors-on-pre-mrna-splicing-across-eukaryotes
#9
Gildas Lepennetier, Francesco Catania
In human, mouse and Drosophila, the spliceosomal complex U1 snRNP (U1) protects transcripts from premature cleavage and polyadenylation at proximal intronic polyadenylation signals (PAS). These U1-mediated effects preserve transcription integrity and are known as telescripting. The watchtower role of U1 throughout transcription is clear. What is less clear is whether cleavage and polyadenylation factors (CPFs) are simply patrolled or if they may actively antagonize U1 recruitment. In addressing this question, we found that in the introns of human, mouse and Drosophila and of 14 other eukaryotes, including multi- and single-celled species, the conserved AATAAA PAS - a major target for CPFs - is selected against...
May 12, 2017: G3: Genes—Genomes—Genetics
https://www.readbyqxmd.com/read/28495751/male-sex-in-houseflies-is-determined-by-mdmd-a-paralog-of-the-generic-splice-factor-gene-cwc22
#10
Akash Sharma, Svenia D Heinze, Yanli Wu, Tea Kohlbrenner, Ian Morilla, Claudia Brunner, Ernst A Wimmer, Louis van de Zande, Mark D Robinson, Leo W Beukeboom, Daniel Bopp
Across species, animals have diverse sex determination pathways, each consisting of a hierarchical cascade of genes and its associated regulatory mechanism. Houseflies have a distinctive polymorphic sex determination system in which a dominant male determiner, the M-factor, can reside on any of the chromosomes. We identified a gene, Musca domesticamale determiner (Mdmd), as the M-factor. Mdmd originated from a duplication of the spliceosomal factor gene CWC22 (nucampholin). Targeted Mdmd disruption results in complete sex reversal to fertile females because of a shift from male to female expression of the downstream genes transformer and doublesex The presence of Mdmd on different chromosomes indicates that Mdmd translocated to different genomic sites...
May 12, 2017: Science
https://www.readbyqxmd.com/read/28495309/group-ii-introns-in-wheat-mitochondria-have-degenerate-structural-features-and-varied-splicing-pathways
#11
Matthew Ngu, Karen Massel, Linda Bonen
Mitochondrial introns in flowering plant genes are virtually all classified as members of the group II ribozyme family although certain structural features have degenerated to varying degrees over evolutionary time. We are interested in the impact that unconventional intron architecture might have on splicing biochemistry in vivo and we have focused in particular on intronic domains V and VI, which for self-splicing introns provide a key component of the catalytic core and the bulged branchpoint adenosine, respectively...
May 8, 2017: International Journal of Biochemistry & Cell Biology
https://www.readbyqxmd.com/read/28488414/a-proteomic-based-investigation-of-potential-copper-responsive-biomarkers-proteins-conceptual-networks-and-metabolic-pathways-featuring-penicillium-janthinellum-from-a%C3%A2-heavy-metal-polluted-ecological-niche
#12
Xin Feng, Jian Xu, Yu Liang, Guo-Li Chen, Xian-Wei Fan, You-Zhi Li
Filamentous fungi-copper (Cu) interactions are very important in the formation of natural ecosystems and the bioremediation of heavy metal pollution. However, important issues at the proteome level remain unclear. We compared six proteomes from Cu-resistant wild-type (WT) Penicillium janthinellum strain GXCR and a Cu-sensitive mutant (EC-6) under 0, 0.5, and 3 mmol/L Cu treatments using iTRAQ. A total of 495 known proteins were identified, and the following conclusions were drawn from the results: Cu tolerance depends on ATP generation and supply, which is relevant to glycolysis pathway activity; oxidative phosphorylation, the TCA cycle, gluconeogenesis, fatty acid synthesis, and metabolism are also affected by Cu; high Cu sensitivity is primarily due to an ATP energy deficit; among ATP generation pathways, Cu-sensitive and Cu-insensitive metabolic steps exist; gluconeogenesis pathway is crucial to the survival of fungi in Cu-containing and sugar-scarce environments; fungi change their proteomes via two routes (from ATP, ATP-dependent RNA helicases (ADRHs), and ribosome biogenesis to proteasomes and from ATP, ADRHs to spliceosomes and/or stress-adapted RNA degradosomes) to cope with changes in Cu concentrations; and unique routes exist through which fungi respond to high environmental Cu...
May 9, 2017: MicrobiologyOpen
https://www.readbyqxmd.com/read/28482101/environment-dependent-regulation-of-spliceosome-activity-by-the-lsm2-8-complex-in-arabidopsis
#13
Cristian Carrasco-López, Tamara Hernández-Verdeja, Carlos Perea-Resa, David Abia, Rafael Catalá, Julio Salinas
Spliceosome activity is tightly regulated to ensure adequate splicing in response to internal and external cues. It has been suggested that core components of the spliceosome, such as the snRNPs, would participate in the control of its activity. The experimental indications supporting this proposition, however, remain scarce, and the operating mechanisms poorly understood. Here, we present genetic and molecular evidence demonstrating that the LSM2-8 complex, the protein moiety of the U6 snRNP, regulates the spliceosome activity in Arabidopsis, and that this regulation is controlled by the environmental conditions...
May 8, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28477131/noncanonical-atm-activation-and-signaling-in-response-to-transcription-blocking-dna-damage
#14
Jurgen A Marteijn, Wim Vermeulen, Maria Tresini
Environmental genotoxins and metabolic byproducts generate DNA lesions that can cause genomic instability and disrupt tissue homeostasis. To ensure genomic integrity, cells employ mechanisms that convert signals generated by stochastic DNA damage into organized responses, including activation of repair systems, cell cycle checkpoints, and apoptotic mechanisms. DNA damage response (DDR) signaling pathways coordinate these responses and determine cellular fates in part, by transducing signals that modulate RNA metabolism...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28466384/splicing-factor-mutations-in-mds-rars-and-mds-mpn-rs-t
#15
REVIEW
Akihide Yoshimi, Omar Abdel-Wahab
Spliceosomal mutations, especially mutations in SF3B1, are frequently (>80%) identified in patients with refractory anemia with ringed sideroblasts (RARS) and myelodysplastic/myeloproliferative neoplasms with ringed sideroblasts and thrombocytosis (MDS/MPN-RS-T; previously known as RARS-T), and SF3B1 mutations have a high positive predictive value for disease phenotype with ringed sideroblasts. These observations suggest that SF3B1 mutations play important roles in the pathogenesis of these disorders and formation of ringed sideroblasts...
June 2017: International Journal of Hematology
https://www.readbyqxmd.com/read/28463775/identifying-dynamic-pathway-interactions-based-on-clinical-information
#16
Shinuk Kim
In this paper, we introduce approaches for inferring dynamic pathway interactions by converting static datasets into dynamic datasets using patients' clinical information. One approach uses survival time-based dynamic datasets, and the other uses grade- and stage-based dynamic datasets. Based on cancer grades and stages, we generated six dynamic levels and obtained two pairs of significant pathways out of twelve enriched pathways. One pair of the pathways included CELL ADHESION MOLECULES CAMS and SYSTEMIC LUPUS ERYTHEMATOSUS (correlation coefficient=1...
April 24, 2017: Computational Biology and Chemistry
https://www.readbyqxmd.com/read/28454538/transcriptomic-and-proteomic-insight-into-the-effects-of-a-defined-european-mistletoe-extract-in-ewing-sarcoma-cells-reveals-cellular-stress-responses
#17
M Twardziok, D Meierhofer, S Börno, B Timmermann, S Jäger, Sengül Boral, A Eggert, C I Delebinski, G Seifert
BACKGROUND: The hydrophobic triterpenes, oleanolic and betulinic acid as well as the hydrophilic mistletoe lectins and viscotoxins possess anticancer properties. They do all occur in combination in European mistletoe (Viscum album L.). Commercial Viscum album L. extracts are aqueous, excluding the insoluble triterpenes. We have previously shown that mistletoe lectins and triterpene acids are effective against Ewing sarcoma in vitro, ex vivo and in vivo. METHODS: We recreated a total mistletoe effect (viscumTT) by combining an aqueous extract (viscum) and a triterpene extract (TT) solubilised with cyclodextrins and analysed the effects of viscumTT and the single extracts on TC-71 Ewing sarcoma cells in vitro by transcriptomic and proteomic profiling...
April 28, 2017: BMC Complementary and Alternative Medicine
https://www.readbyqxmd.com/read/28446598/the-histone-variant-h2a-z-promotes-efficient-cotranscriptional-splicing-in-s-cerevisiae
#18
Lauren T Neves, Stephen Douglass, Roberto Spreafico, Srivats Venkataramanan, Tracy L Kress, Tracy L Johnson
In eukaryotes, a dynamic ribonucleic protein machine known as the spliceosome catalyzes the removal of introns from premessenger RNA (pre-mRNA). Recent studies show the processes of RNA synthesis and RNA processing to be spatio-temporally coordinated, indicating that RNA splicing takes place in the context of chromatin. H2A.Z is a highly conserved histone variant of the canonical histone H2A. In Saccharomyces cerevisiae, H2A.Z is deposited into chromatin by the SWR-C complex, is found near the 5' ends of protein-coding genes, and has been implicated in transcription regulation...
April 1, 2017: Genes & Development
https://www.readbyqxmd.com/read/28446597/the-histone-variant-h2a-z-promotes-splicing-of-weak-introns
#19
Kelly E Nissen, Christina M Homer, Colm J Ryan, Michael Shales, Nevan J Krogan, Kristin L Patrick, Christine Guthrie
Multiple lines of evidence implicate chromatin in the regulation of premessenger RNA (pre-mRNA) splicing. However, the influence of chromatin factors on cotranscriptional splice site usage remains unclear. Here we investigated the function of the highly conserved histone variant H2A.Z in pre-mRNA splicing using the intron-rich model yeast Schizosaccharomyces pombe Using epistatic miniarray profiles (EMAPs) to survey the genetic interaction landscape of the Swr1 nucleosome remodeling complex, which deposits H2A...
April 1, 2017: Genes & Development
https://www.readbyqxmd.com/read/28445500/sf3b1-is-a-stress-sensitive-splicing-factor-that-regulates-both-hsf1-concentration-and-activity
#20
Karen S Kim Guisbert, Eric Guisbert
The heat shock response (HSR) is a well-conserved, cytoprotective stress response that activates the HSF1 transcription factor. During severe stress, cells inhibit mRNA splicing which also serves a cytoprotective function via inhibition of gene expression. Despite their functional interconnectedness, there have not been any previous reports of crosstalk between these two pathways. In a genetic screen, we identified SF3B1, a core component of the U2 snRNP subunit of the spliceosome, as a regulator of the heat shock response in Caenorhabditis elegans...
2017: PloS One
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