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https://www.readbyqxmd.com/read/28203566/increased-spontaneous-recombination-in-rnase-h2-deficient-cells-arises-from-multiple-contiguous-rnmps-and-not-from-single-rnmp-residues-incorporated-by-dna-polymerase-epsilon
#1
Anastasiya Epshtein, Catherine J Potenski, Hannah L Klein
Ribonucleotides can become embedded in DNA from insertion by DNA polymerases, failure to remove Okazaki fragment primers, R-loops that can prime replication, and RNA/cDNA-mediated recombination. RNA:DNA hybrids are removed by RNase H enzymes. Single rNMPs in DNA are removed by RNase H2 and if they remain on the leading strand, can lead to mutagenesis in a Top1-dependent pathway. rNMPs in DNA can also stimulate genome instability, among which are homologous recombination gene conversion events. We previously found that, similar to the rNMP-stimulated mutagenesis, rNMP-stimulated recombination was also Top1-dependent...
June 2016: Microbial Cell
https://www.readbyqxmd.com/read/28182989/6-cyclohexylmethyl-3-hydroxypyrimidine-2-4-dione-as-an-inhibitor-scaffold-of-hiv-reverase-transcriptase-impacts-of-the-3-oh-on-inhibiting-rnase-h-and-polymerase
#2
Jing Tang, Karen A Kirby, Andrew D Huber, Mary C Casey, Juan Ji, Daniel J Wilson, Stefan G Sarafianos, Zhengqiang Wang
3-Hydroxypyrimidine-2,4-dione (HPD) represents a versatile chemical core in the design of inhibitors of human immunodeficiency virus (HIV) reverse transcriptase (RT)-associated RNase H and integrase strand transfer (INST). We report herein the design, synthesis and biological evaluation of an HPD subtype (4) featuring a cyclohexylmethyl group at the C-6 position. Antiviral testing showed that most analogues of 4 inhibited HIV-1 in the low nanomolar to submicromolar range, without cytotoxicity at concentrations up to 100 μM...
January 30, 2017: European Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/28182633/characterizing-the-coding-region-determinant-binding-protein-crd-bp-microphthalmia-associated-transcription-factor-mitf-mrna-interaction
#3
Gerrit van Rensburg, Sebastian Mackedenski, Chow H Lee
Coding region determinant-binding protein (CRD-BP) binds to the 3'-UTR of microphthalmia-associated transcription factor (MITF) mRNA to prevent its targeted degradation by miR-340. Here, we aim to further understand the molecular interaction between CRD-BP and MITF RNA. Using point mutation in the GXXG motif of each KH domains, we showed that all four KH domains of CRD-BP are important for their physical association with MITF RNA. We mapped the CRD-BP-binding site in the 3'-UTR of MITF RNA from nts 1330-1740 and showed that the 49-nt fragment 1621-1669 is the minimal size MITF RNA for binding...
2017: PloS One
https://www.readbyqxmd.com/read/28159842/direct-visualization-of-rna-dna-primer-removal-from-okazaki-fragments-provides-support-for-flap-cleavage-and-exonucleolytic-pathways-in-eukaryotic-cells
#4
Bochao Liu, Jiazhi Hu, Jingna Wang, Daochun Kong
During DNA replication in eukaryotic cells, short single-stranded DNA segments known as Okazaki fragments are first synthesized on the lagging strand. The Okazaki fragments originate from ~35 nt long RNA-DNA primers. After Okazaki fragment synthesis, these primers must be removed to allow fragment joining into a continuous lagging strand. To date, the models of enzymatic machinery that removes the RNA-DNA primers has come almost exclusively from biochemical reconstitution studies and some genetic interaction assays, and there is little direct evidence to confirm these models...
February 3, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28158275/early-endonuclease-mediated-evasion-of-rna-sensing-ensures-efficient-coronavirus-replication
#5
Eveline Kindler, Cristina Gil-Cruz, Julia Spanier, Yize Li, Jochen Wilhelm, Huib H Rabouw, Roland Züst, Mihyun Hwang, Philip V'kovski, Hanspeter Stalder, Sabrina Marti, Matthias Habjan, Luisa Cervantes-Barragan, Ruth Elliot, Nadja Karl, Christina Gaughan, Frank J M van Kuppeveld, Robert H Silverman, Markus Keller, Burkhard Ludewig, Cornelia C Bergmann, John Ziebuhr, Susan R Weiss, Ulrich Kalinke, Volker Thiel
Coronaviruses are of veterinary and medical importance and include highly pathogenic zoonotic viruses, such as SARS-CoV and MERS-CoV. They are known to efficiently evade early innate immune responses, manifesting in almost negligible expression of type-I interferons (IFN-I). This evasion strategy suggests an evolutionary conserved viral function that has evolved to prevent RNA-based sensing of infection in vertebrate hosts. Here we show that the coronavirus endonuclease (EndoU) activity is key to prevent early induction of double-stranded RNA (dsRNA) host cell responses...
February 2017: PLoS Pathogens
https://www.readbyqxmd.com/read/28124143/molecular-characterization-of-previously-elusive-badnaviruses-associated-with-symptomatic-cacao-in-the-new-world
#6
Nomatter Chingandu, Muhammad Zia-Ur-Rehman, Thyail N Sreenivasan, Surendra Surujdeo-Maharaj, Pathmanathan Umaharan, Osman A Gutierrez, Judith K Brown
Suspected virus-like symptoms were observed in cacao plants in Trinidad during 1943, and the viruses associated with these symptoms were designated as strains A and B of cacao Trinidad virus (CTV). However, viral etiology has not been demonstrated for either phenotype. Total DNA was isolated from symptomatic cacao leaves exhibiting the CTV A and B phenotypes and subjected to Illumina HiSeq and Sanger DNA sequencing. Based on de novo assembly, two apparently full-length badnavirus genomes of 7,533 and 7,454 nucleotides (nt) were associated with CTV strain A and B, respectively...
January 25, 2017: Archives of Virology
https://www.readbyqxmd.com/read/28115465/targeted-crispr-disruption-reveals-a-role-for-rnase-mrp-rna-in-human-preribosomal-rna-processing
#7
Katherine C Goldfarb, Thomas R Cech
MRP RNA is an abundant, essential noncoding RNA whose functions have been proposed in yeast but are incompletely understood in humans. Mutations in the genomic locus for MRP RNA cause pleiotropic human diseases, including cartilage hair hypoplasia (CHH). Here we applied CRISPR-Cas9 genome editing to disrupt the endogenous human MRP RNA locus, thereby attaining what has eluded RNAi and RNase H experiments: elimination of MRP RNA in the majority of cells. The resulting accumulation of ribosomal RNA (rRNA) precursor-analyzed by RNA fluorescent in situ hybridization (FISH), Northern blots, and RNA sequencing-implicates MRP RNA in pre-rRNA processing...
January 1, 2017: Genes & Development
https://www.readbyqxmd.com/read/28108662/coordination-between-the-polymerase-and-rnase-h-activity-of-hiv-1-reverse-transcriptase
#8
Małgorzata Figiel, Miroslav Krepl, Jarosław Poznański, Agnieszka Gołąb, Jiří Šponer, Marcin Nowotny
Replication of human immunodeficiency virus 1 (HIV-1) involves conversion of its single-stranded RNA genome to double-stranded DNA, which is integrated into the genome of the host. This conversion is catalyzed by reverse transcriptase (RT), which possesses DNA polymerase and RNase H domains. The available crystal structures suggest that at any given time the RNA/DNA substrate interacts with only one active site of the two domains of HIV-1 RT. Unknown is whether a simultaneous interaction of the substrate with polymerase and RNase H active sites is possible...
January 20, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28100693/viral-genome-packaging-terminase-cleaves-dna-using-the-canonical-ruvc-like-two-metal-catalysis-mechanism
#9
Rui-Gang Xu, Huw T Jenkins, Maria Chechik, Elena V Blagova, Anna Lopatina, Evgeny Klimuk, Leonid Minakhin, Konstantin Severinov, Sandra J Greive, Alfred A Antson
Bacteriophages and large dsDNA viruses encode sophisticated machinery to translocate their DNA into a preformed empty capsid. An essential part of this machine, the large terminase protein, processes viral DNA into constituent units utilizing its nuclease activity. Crystal structures of the large terminase nuclease from the thermophilic bacteriophage G20c show that it is most similar to the RuvC family of the RNase H-like endonucleases. Like RuvC proteins, the nuclease requires either Mn(2+), Mg(2+) or Co(2+) ions for activity, but is inactive with Zn(2+) and Ca(2+) High resolution crystal structures of complexes with different metals reveal that in the absence of DNA, only one catalytic metal ion is accommodated in the active site...
January 18, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28092684/biallelic-mutations-in-the-3-exonuclease-toe1-cause-pontocerebellar-hypoplasia-and-uncover-a-role-in-snrna-processing
#10
Rea M Lardelli, Ashleigh E Schaffer, Veerle R C Eggens, Maha S Zaki, Stephanie Grainger, Shashank Sathe, Eric L Van Nostrand, Zinayida Schlachetzki, Basak Rosti, Naiara Akizu, Eric Scott, Jennifer L Silhavy, Laura Dean Heckman, Rasim Ozgur Rosti, Esra Dikoglu, Anne Gregor, Alicia Guemez-Gamboa, Damir Musaev, Rohit Mande, Ari Widjaja, Tim L Shaw, Sebastian Markmiller, Isaac Marin-Valencia, Justin H Davies, Linda de Meirleir, Hulya Kayserili, Umut Altunoglu, Mary Louise Freckmann, Linda Warwick, David Chitayat, Susan Blaser, Ahmet Okay Çağlayan, Kaya Bilguvar, Huseyin Per, Christina Fagerberg, Henrik T Christesen, Maria Kibaek, Kimberly A Aldinger, David Manchester, Naomichi Matsumoto, Kazuhiro Muramatsu, Hirotomo Saitsu, Masaaki Shiina, Kazuhiro Ogata, Nicola Foulds, William B Dobyns, Neil C Chi, David Traver, Luigina Spaccini, Stefania Maria Bova, Stacey B Gabriel, Murat Gunel, Enza Maria Valente, Marie-Cecile Nassogne, Eric J Bennett, Gene W Yeo, Frank Baas, Jens Lykke-Andersen, Joseph G Gleeson
Deadenylases are best known for degrading the poly(A) tail during mRNA decay. The deadenylase family has expanded throughout evolution and, in mammals, consists of 12 Mg(2+)-dependent 3'-end RNases with substrate specificity that is mostly unknown. Pontocerebellar hypoplasia type 7 (PCH7) is a unique recessive syndrome characterized by neurodegeneration and ambiguous genitalia. We studied 12 human families with PCH7, uncovering biallelic, loss-of-function mutations in TOE1, which encodes an unconventional deadenylase...
January 16, 2017: Nature Genetics
https://www.readbyqxmd.com/read/28088905/update-on-recent-developments-in-small-molecular-hiv-1-rnase-h-inhibitors-2013-2016-opportunities-and-challenges
#11
Xueshun Wang, Ping Gao, Luis Menéndez-Arias, Xinyong Liu, Peng Zhan
Combinations of antiretroviral drugs are successfully used to treat HIV-infected patients. However, drug resistance is a major problem that makes discovery of new antiretroviral drugs an ongoing priority. The ribonuclease H (RNase H) activity of the HIV-1 reverse transcriptase catalyzes the selective hydrolysis of the RNA strand of RNA:DNA heteroduplex replication intermediates, and represents an attractive unexploited target for drug development. This review reports on recent progress in the characterization of HIV-1 RNase H inhibitors from 2013 to 2016, describing their chemical structures, structure-activity relationship and binding modes...
January 13, 2017: Current Medicinal Chemistry
https://www.readbyqxmd.com/read/28077560/mechanistic-insights-into-type-i-toxin-antitoxin-systems-in-helicobacter-pylori-the-importance-of-mrna-folding-in-controlling-toxin-expression
#12
Hélène Arnion, Dursun Nizam Korkut, Sara Masachis Gelo, Sandrine Chabas, Jérémy Reignier, Isabelle Iost, Fabien Darfeuille
Type I toxin-antitoxin (TA) systems have been identified in a wide range of bacterial genomes. Here, we report the characterization of a new type I TA system present on the chromosome of the major human gastric pathogen, Helicobacter pylori We show that the aapA1 gene encodes a 30 amino acid peptide whose artificial expression in H. pylori induces cell death. The synthesis of this toxin is prevented by the transcription of an antitoxin RNA, named IsoA1, expressed on the opposite strand of the toxin gene. We further reveal additional layers of post-transcriptional regulation that control toxin expression: (i) transcription of the aapA1 gene generates a full-length transcript whose folding impedes translation (ii) a 3' end processing of this message generates a shorter transcript that, after a structural rearrangement, becomes translatable (iii) but this rearrangement also leads to the formation of two stem-loop structures allowing formation of an extended duplex with IsoA1 via kissing-loop interactions...
January 10, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28076346/cryo-em-structure-of-a-human-spliceosome-activated-for-step-2-of-splicing
#13
Karl Bertram, Dmitry E Agafonov, Wen-Ti Liu, Olexandr Dybkov, Cindy L Will, Klaus Hartmuth, Henning Urlaub, Berthold Kastner, Holger Stark, Reinhard Lu Hrmann
Spliceosome rearrangements facilitated by RNA helicase Prp16 before catalytic step 2 of splicing are poorly understood. Here we report a 3D cryo-electron microscopy structure of the human spliceosomal C complex stalled directly after Prp16 action (C*). The architecture of the catalytic U2-U6 RNP core of the human C* spliceosome is highly similar to that of the yeast pre-Prp16 C complex. However, in C* the branched intron region is separated (by ~20 Å) from the catalytic centre, and its position close to the U6 snRNA ACAGA box is stabilised by interactions with the Prp8 RNase H-like and Prp17 WD40 domains...
January 11, 2017: Nature
https://www.readbyqxmd.com/read/28065739/r-loop-depletion-by-over-expressed-rnase-h1-in-mouse-b-cells-increases-activation-induced-deaminase-access-to-the-transcribed-strand-without-altering-frequency-of-isotype-switching
#14
Robert W Maul, Hyongi Chon, Kiran Sakhuja, Susana M Cerritelli, Lina A Gugliotti, Patricia J Gearhart, Robert J Crouch
R-loops, three-strand structures consisting of mRNA hybridized to the complementary DNA and a single-stranded DNA loop, are formed in switch regions on the heavy-chain immunoglobulin locus. To determine if R-loops have a direct effect on any of the steps involved in isotype switching, we generated a transgenic mouse that over-expressed RNase H1, an enzyme that cleaves the RNA of RNA/DNA hybrids in B cells. R-loops in the switch μ region were depleted by 70% in ex vivo activated splenic B cells. Frequencies of isotype switching to IgG1, IgG2b, IgG2c, and IgG3 were the same as C57BL/6 control cells...
January 6, 2017: Journal of Molecular Biology
https://www.readbyqxmd.com/read/28038925/rapid-monitoring-of-rna-degradation-activity-in%C3%A2-vivo-for-mammalian-cells
#15
Hidenori Tani, Hiroaki Sato, Masaki Torimura
We have developed a rapid fluorescence assay based on fluorescence resonance energy transfer (FRET) for the monitoring of RNA degradation activity in mammalian cells. In this technique, double-stranded RNA (dsRNA) fluorescent probes are used. The dsRNA fluorescent probes consist of a 5' fluorophore-labeled strand hybridized to a 3' quencher-labeled strand, and the fluorescent dye is quenched by a quencher dye. When the dsRNA is degraded by nascent RNases in cells, the fluorescence emission of the fluorophore is induced following the degradation of the double strands...
December 23, 2016: Journal of Bioscience and Bioengineering
https://www.readbyqxmd.com/read/28026819/-nitrobenzofuroxane-derivatives-as-dual-action-hiv-1-inhibitors
#16
S P Korolev, M A Pustovarova, A M Starosotnikov, M A Bastrakov, Yu Yu Agapkina, S A Shevelev, M B Gottikh
Human immunodeficiency virus first type (HIV-1) is a main cause of one of the most dangerous diseases, AIDS. The search for new inhibitors of the virus still remains an urgent task. One approach to suppress the HIV infection is to use a double-acting inhibitors, i.e. inhibitors directed to two stages of the viral life cycle. The catalytic domain of HIV-1 integrase has a similar spatial organization with ribonuclease (RNase H) domain of HIV-1 reverse transcriptase, and approach aimed to create HIV-1 integrase and RNase H double-acting is very promising...
November 2016: Biomedit︠s︡inskai︠a︡ Khimii︠a︡
https://www.readbyqxmd.com/read/28003490/lineage-a-betacoronavirus-ns2-proteins-and-homologous-torovirus-berne-pp1a-carboxyterminal-domain-are-phosphodiesterases-that-antagonize-activation-of-rnase-l
#17
Stephen A Goldstein, Joshua M Thornbrough, Rong Zhang, Babal K Jha, Yize Li, Ruth Elliott, Katherine Quiroz-Figueroa, Annie I Chen, Robert H Silverman, Susan R Weiss
: Viruses in the family Coronaviridae, with the Nidovirus order, are etiologic agents of a range of human and animal diseases, including both mild and severe respiratory disease in humans. These viruses encode conserved replicase and structural proteins, and more diverse accessory proteins in the 3' end of their genomes that often act as host cell antagonists. We have previously shown that 2', 5' phosphodiesterases (PDE) encoded by the prototypical Betacoronavirus, mouse hepatitis virus (MHV), Middle East respiratory syndrome-associated coronavirus antagonize the oligoadenylate - ribonuclease L (OAS-RNase L) pathway...
December 21, 2016: Journal of Virology
https://www.readbyqxmd.com/read/27959588/exosome-mediated-telomere-instability-in-human-breast-epithelial-cancer-cells-after-x-irradiation
#18
Ammar H J Al-Mayah, Scott J Bright, Debbie A Bowler, Predrag Slijepcevic, Edwin Goodwin, Munira A Kadhim
In directly irradiating cells, telomere metabolism is altered and similar effects have been observed in nontargeted cells. Exosomes and their cargo play dominant roles in communicating radiation-induced bystander effects with end points related to DNA damage. Here we report novel evidence that exosomes are also responsible for inducing telomere-related bystander effects. Breast epithelial cancer cells were exposed to either 2 Gy X rays, or exposed to irradiated cell conditioned media (ICCM), or exosomes purified from ICCM...
January 2017: Radiation Research
https://www.readbyqxmd.com/read/27938663/rnase-h-enables-efficient-repair-of-r-loop-induced-dna-damage
#19
Jeremy D Amon, Douglas Koshland
R-loops, three-stranded structures that form when transcripts hybridize to chromosomal DNA, are potent agents of genome instability. This instability has been explained by the ability of R-loops to induce DNA damage. Here, we show that persistent R-loops also compromise DNA repair. Depleting endogenous RNase H activity impairs R-loop removal in Saccharomyces cerevisiae, causing DNA damage that occurs preferentially in the repetitive ribosomal DNA locus (rDNA). We analyzed the repair kinetics of this damage and identified mutants that modulate repair...
December 10, 2016: ELife
https://www.readbyqxmd.com/read/27936595/physiological-mg-2-conditions-significantly-alter-the-inhibition-of-hiv-1-and-hiv-2-reverse-transcriptases-by-nucleoside-and-non-nucleoside-inhibitors-in-vitro
#20
Vasudevan Achuthan, Kamlendra Singh, Jeffrey J DeStefano
Reverse transcriptases (RTs) are typically assayed in vitro with 5-10 mM Mg(2+), whereas the free Mg(2+) concentration in cells is much lower. Artificially high Mg(2+) concentrations used in vitro can misrepresent different properties of human immunodeficiency virus (HIV) RT, including fidelity, catalysis, pausing, and RNase H activity. Here, we analyzed nucleoside (NRTIs) and non-nucleoside RT inhibitors (NNRTIs) in primer extension assays at different concentrations of free Mg(2+). At low concentrations of Mg(2+), NRTIs and dideoxynucleotides (AZTTP, ddCTP, ddGTP, and 3TCTP) inhibited HIV-1 and HIV-2 RT synthesis less efficiently than they did with large amounts of Mg(2+), whereas inhibition by the "translocation-defective RT inhibitor" EFdA (4'-ethynyl-2-fluoro-2'-deoxyadenosine) was unaffected by Mg(2+) concentrations...
December 27, 2016: Biochemistry
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