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https://www.readbyqxmd.com/read/28529475/fragile-x-associated-tremor-ataxia-syndrome-from-molecular-pathogenesis-to-development-of-therapeutics
#1
REVIEW
Ha Eun Kong, Juan Zhao, Shunliang Xu, Peng Jin, Yan Jin
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder caused by a premutation CGG repeat expansion (55-200 repeats) within the 5' UTR of the fragile X gene (FMR1). FXTAS is characterized by intension tremor, cerebellar ataxia, progressive neurodegeneration, parkinsonism and cognitive decline. The development of transgenic mouse and Drosophila melanogaster models carrying an expanded CGG repeat has yielded valuable insight into the pathophysiology of FXTAS. To date, we know of two main molecular mechanisms of this disorder: (1) a toxic gain of function of the expanded CGG-repeat FMR1 mRNA, which results in the binding/sequestration of the CGG-binding proteins; and (2) CGG repeat-associated non-AUG-initiated (RAN) translation, which generates a polyglycine peptide toxic to cells...
2017: Frontiers in Cellular Neuroscience
https://www.readbyqxmd.com/read/28498974/strong-transcription-blockage-mediated-by-r-loop-formation-within-a-g-rich-homopurine-homopyrimidine-sequence-localized-in-the-vicinity-of-the-promoter
#2
Boris P Belotserkovskii, Jane Hae Soo Shin, Philip C Hanawalt
Guanine-rich (G-rich) homopurine-homopyrimidine nucleotide sequences can block transcription with an efficiency that depends upon their orientation, composition and length, as well as the presence of negative supercoiling or breaks in the non-template DNA strand. We report that a G-rich sequence in the non-template strand reduces the yield of T7 RNA polymerase transcription by more than an order of magnitude when positioned close (9 bp) to the promoter, in comparison to that for a distal (∼250 bp) location of the same sequence...
May 11, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28487353/the-chromatin-remodelling-factor-atrx-suppresses-r-loops-in-transcribed-telomeric-repeats
#3
Diu Tt Nguyen, Hsiao Phin J Voon, Barbara Xella, Caroline Scott, David Clynes, Christian Babbs, Helena Ayyub, Jon Kerry, Jacqueline A Sharpe, Jackie A Sloane-Stanley, Sue Butler, Chris A Fisher, Nicki E Gray, Thomas Jenuwein, Douglas R Higgs, Richard J Gibbons
ATRX is a chromatin remodelling factor found at a wide range of tandemly repeated sequences including telomeres (TTAGGG)n ATRX mutations are found in nearly all tumours that maintain their telomeres via the alternative lengthening of telomere (ALT) pathway, and ATRX is known to suppress this pathway. Here, we show that recruitment of ATRX to telomeric repeats depends on repeat number, orientation and, critically, on repeat transcription. Importantly, the transcribed telomeric repeats form RNA-DNA hybrids (R-loops) whose abundance correlates with the recruitment of ATRX Here, we show loss of ATRX is also associated with increased R-loop formation...
May 9, 2017: EMBO Reports
https://www.readbyqxmd.com/read/28481984/the-dna-damage-response-ddr-is-induced-by-the-c9orf72-repeat-expansion-in-amyotrophic-lateral-sclerosis
#4
Manal A Farg, Anna Konopka, Kai Ying Soo, Daisuke Ito, Julie D Atkin
Amyotrophic lateral sclerosis (ALS) is a rapidly progressing neurodegenerative disease affecting motor neurons. Hexanucleotide (GGGGCC) repeat expansions in a non-coding region of C9orf72 are the major cause of familial ALS and frontotemporal dementia (FTD) worldwide. The C9orf72 repeat expansion undergoes repeat-associated non-ATG (RAN) translation to produce five dipeptide repeat proteins (DRPs), including poly(GR) and poly(PR). Whilst it remains unclear how mutations in C9orf72 lead to neurodegeneration in ALS/FTD, dysfunction to the nucleolus and R loop formation are implicated as pathogenic mechanisms...
May 8, 2017: Human Molecular Genetics
https://www.readbyqxmd.com/read/28477131/noncanonical-atm-activation-and-signaling-in-response-to-transcription-blocking-dna-damage
#5
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/28471430/dna-rna-hybrids-the-risks-of-dna-breakage-during-transcription
#6
Andrés Aguilera, Belén Gómez-González
Although R loops can occur at different genomic locations, the factors that determine their formation and frequency remain unclear. Emerging evidence indicates that DNA breaks stimulate DNA-RNA hybrid formation. Here, we discuss the possibility that formation of hybrids may be an inevitable risk of DNA breaks that occur within actively transcribed regions. While such hybrids must be removed to permit repair, their potential role as repair intermediates remains to be established.
May 4, 2017: Nature Structural & Molecular Biology
https://www.readbyqxmd.com/read/28447783/real-time-detection-reveals-responsive-cotranscriptional-formation-of-persistent-intramolecular-dna-and-intermolecular-dna-rna-hybrid-g-quadruplexes-stabilized-by-r-loop
#7
Yang Zhao, Jia-Yu Zhang, Zong-Yu Zhang, Tan-Jun Tong, Yu-Hua Hao, Zheng Tan
G-quadruplex (GQ) structures are implicated in important physiological and pathological processes. Millions of GQ-forming motifs are enriched near transcription start sites (TSSs) of animal genes. Transcription can induce the formation of GQs, which in turn regulate transcription. The kinetics of the formation and persistence of GQs in transcription is crucial for the role they play but has not yet been explored. We established a method based on the fluorescence resonance energy transfer (FRET) technique to monitor in real-time the cotranscriptional formation and post-transcriptional persistence of GQs in DNA...
May 9, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28437608/crispr-cas9-mediated-dna-unwinding-detected-using-site-directed-spin-labeling
#8
Narin S Tangprasertchai, Rosa Di Felice, Xiaojun Zhang, Ian M Slaymaker, Carolina Vazquez Reyes, Wei Jiang, Remo Rohs, Peter Z Qin
The RNA-guided CRISPR-Cas9 nuclease has revolutionized genome engineering, yet its mechanism for DNA target selection is not fully understood. A crucial step in Cas9 target recognition involves unwinding of the DNA duplex to form a three-stranded R-loop structure. Work reported here demonstrates direct detection of Cas9-mediated DNA unwinding by a combination of site-directed spin labeling and molecular dynamics simulations. The results support a model in which the unwound nontarget strand is stabilized by a positively charged patch located between the two nuclease domains of Cas9 and reveal uneven increases in flexibility along the unwound nontarget strand upon scissions of the DNA backbone...
May 3, 2017: ACS Chemical Biology
https://www.readbyqxmd.com/read/28431230/structural-basis-for-guide-rna-processing-and-seed-dependent-dna-targeting-by-crispr-cas12a
#9
Daan C Swarts, John van der Oost, Martin Jinek
The CRISPR-associated protein Cas12a (Cpf1), which has been repurposed for genome editing, possesses two distinct nuclease activities: endoribonuclease activity for processing its own guide RNAs and RNA-guided DNase activity for target DNA cleavage. To elucidate the molecular basis of both activities, we determined crystal structures of Francisella novicida Cas12a bound to guide RNA and in complex with an R-loop formed by a non-cleavable guide RNA precursor and a full-length target DNA. Corroborated by biochemical experiments, these structures reveal the mechanisms of guide RNA processing and pre-ordering of the seed sequence in the guide RNA that primes Cas12a for target DNA binding...
April 20, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28429714/pif1-family-dna-helicases-suppress-r-loop-mediated-genome-instability-at-trna-genes
#10
Phong Lan Thao Tran, Thomas J Pohl, Chi-Fu Chen, Angela Chan, Sebastian Pott, Virginia A Zakian
Saccharomyces cerevisiae encodes two Pif1 family DNA helicases, Pif1 and Rrm3. Rrm3 promotes DNA replication past stable protein complexes at tRNA genes (tDNAs). We identify a new role for the Pif1 helicase: promotion of replication and suppression of DNA damage at tDNAs. Pif1 binds multiple tDNAs, and this binding is higher in rrm3Δ cells. Accumulation of replication intermediates and DNA damage at tDNAs is higher in pif1Δ rrm3Δ than in rrm3Δ cells. DNA damage at tDNAs in the absence of these helicases is suppressed by destabilizing R-loops while Pif1 and Rrm3 binding to tDNAs is increased upon R-loop stabilization...
April 21, 2017: Nature Communications
https://www.readbyqxmd.com/read/28418376/a-circrna-from-sepallata3-regulates-splicing-of-its-cognate-mrna-through-r-loop-formation
#11
Vanessa M Conn, Véronique Hugouvieux, Aditya Nayak, Stephanie A Conos, Giovanna Capovilla, Gökhan Cildir, Agnès Jourdain, Vinay Tergaonkar, Markus Schmid, Chloe Zubieta, Simon J Conn
Circular RNAs (circRNAs) are a diverse and abundant class of hyper-stable, non-canonical RNAs that arise through a form of alternative splicing (AS) called back-splicing. These single-stranded, covalently-closed circRNA molecules have been identified in all eukaryotic kingdoms of life(1), yet their functions have remained elusive. Here, we report that circRNAs can be used as bona fide biomarkers of functional, exon-skipped AS variants in Arabidopsis, including in the homeotic MADS-box transcription factor family...
April 18, 2017: Nature Plants
https://www.readbyqxmd.com/read/28412545/dna-topoisomerase-1-prevents-r-loop-accumulation-to-modulate-auxin-regulated-root-development-in-rice
#12
Sarfraz Shafiq, Chunli Chen, Jing Yang, Lingling Cheng, Fei Ma, Emilie Widemann, Qianwen Sun
R-loop structures (RNA:DNA hybrids) have important functions in many biological processes, including transcriptional regulation and genome instability among diverse organisms. DNA topoisomerase 1 (TOP1), an essential manipulator of DNA topology during RNA transcription and DNA replication processes, can prevent R-loop accumulation by removing the positive and negative DNA supercoiling that is made by RNA polymerases during transcription. TOP1 is required for plant development, but little is known about its function in preventing co-transcriptional R-loop accumulation in various biological processes in plants...
April 12, 2017: Molecular Plant
https://www.readbyqxmd.com/read/28408437/the-myc-mrna-3-utr-couples-rna-polymerase-ii-function-to-glutamine-and-ribonucleotide-levels
#13
Francesca R Dejure, Nadine Royla, Steffi Herold, Jacqueline Kalb, Susanne Walz, Carsten P Ade, Guido Mastrobuoni, Jens T Vanselow, Andreas Schlosser, Elmar Wolf, Stefan Kempa, Martin Eilers
Deregulated expression of MYC enhances glutamine utilization and renders cell survival dependent on glutamine, inducing "glutamine addiction". Surprisingly, colon cancer cells that express high levels of MYC due to WNT pathway mutations are not glutamine-addicted but undergo a reversible cell cycle arrest upon glutamine deprivation. We show here that glutamine deprivation suppresses translation of endogenous MYC via the 3'-UTR of the MYC mRNA, enabling escape from apoptosis. This regulation is mediated by glutamine-dependent changes in adenosine-nucleotide levels...
April 13, 2017: EMBO Journal
https://www.readbyqxmd.com/read/28406751/repetitive-dna-loci-and-their-modulation-by-the-non-canonical-nucleic-acid-structures-r-loops-and-g-quadruplexes
#14
REVIEW
Amanda C Hall, Lauren A Ostrowski, Violena Pietrobon, Karim Mekhail
Cells have evolved intricate mechanisms to maintain genome stability despite allowing mutational changes to drive evolutionary adaptation. Repetitive DNA sequences, which represent the bulk of most genomes, are a major threat to genome stability often driving chromosome rearrangements and disease. The major source of repetitive DNA sequences and thus the most vulnerable constituents of the genome are the rDNA (rDNA) repeats, telomeres, and transposable elements. Maintaining the stability of these loci is critical to overall cellular fitness and lifespan...
March 4, 2017: Nucleus
https://www.readbyqxmd.com/read/28375731/crispr-cas9-structures-and-mechanisms
#15
Fuguo Jiang, Jennifer A Doudna
Many bacterial clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated (Cas) systems employ the dual RNA-guided DNA endonuclease Cas9 to defend against invading phages and conjugative plasmids by introducing site-specific double-stranded breaks in target DNA. Target recognition strictly requires the presence of a short protospacer adjacent motif (PAM) flanking the target site, and subsequent R-loop formation and strand scission are driven by complementary base pairing between the guide RNA and target DNA, Cas9-DNA interactions, and associated conformational changes...
March 30, 2017: Annual Review of Biophysics
https://www.readbyqxmd.com/read/28349431/detection-and-characterization-of-r-loop-structures
#16
Raquel Boque-Sastre, Marta Soler, Sonia Guil
R loops are special three stranded nucleic acid structures that comprise a nascent RNA hybridized with the DNA template strand, leaving a non-template DNA single-stranded. More specifically, R loops form in vivo as G-rich RNA transcripts invade the DNA duplex and anneal to the template strand to generate an RNA:DNA hybrid, leaving the non-template, G-rich DNA strand in a largely single-stranded conformation (Aguilera and Garcia-Muse, Mol Cell 46:115-124, 2012).DNA-RNA hybrids are a natural occurrence within eukaryotic cells, with levels of these hybrids increasing at sites with high transcriptional activity, such as during transcription initiation, repression, and elongation...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28349430/rna-fish-to-study-regulatory-rna-at-the-site-of-transcription
#17
Marta Soler, Raquel Boque-Sastre, Sonia Guil
The increasing role of all types of regulatory RNAs in the orchestration of cellular programs has enhanced the development of a variety of techniques that allow its precise detection, quantification, and functional scrutiny. Recent advances in imaging and fluoresecent in situ hybridization (FISH) methods have enabled the utilization of user-friendly protocols that provide highly sensitive and accurate detection of ribonucleic acid molecules at both the single cell and subcellular levels. We herein describe the approach originally developed by Stellaris(®), in which the target RNA molecule is fluoresecently labeled with multiple tiled complementary probes each carrying a fluorophore, thus improving sensitivity and reducing the chance of false positives...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28341774/rna-dna-hybrid-r-loop-immunoprecipitation-mapping-an-analytical-workflow-to-evaluate-inherent-biases
#18
László Halász, Zsolt Karányi, Beáta Boros-Oláh, Tímea Rózsa, Éva Sipos, Éva Nagy, Ágnes Mosolygó-L, Anett Mázló, Éva Rajnavölgyi, Gábor Halmos, Lóránt Székvölgyi
The impact of R-loops on the physiology and pathology of chromosomes has been demonstrated extensively by chromatin biology research. The progress in this field has been driven by technological advancement of R-loop mapping methods that largely relied on a single approach, DNA-RNA immunoprecipitation (DRIP). Most of the DRIP protocols use the experimental design that was developed by a few laboratories, without paying attention to the potential caveats that might affect the outcome of RNA-DNA hybrid mapping...
March 24, 2017: Genome Research
https://www.readbyqxmd.com/read/28318821/snf2-family-protein-fft3-suppresses-nucleosome-turnover-to-promote-epigenetic-inheritance-and-proper-replication
#19
Nitika Taneja, Martin Zofall, Vanivilasini Balachandran, Gobi Thillainadesan, Tomoyasu Sugiyama, David Wheeler, Ming Zhou, Shiv I S Grewal
Heterochromatin can be epigenetically inherited in cis, leading to stable gene silencing. However, the mechanisms underlying heterochromatin inheritance remain unclear. Here, we identify Fft3, a fission yeast homolog of the mammalian SMARCAD1 SNF2 chromatin remodeler, as a factor uniquely required for heterochromatin inheritance, rather than for de novo assembly. Importantly, we find that Fft3 suppresses turnover of histones at heterochromatic loci to facilitate epigenetic transmission of heterochromatin in cycling cells...
April 6, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28314779/an-atr-dependent-function-for-the-ddx19-rna-helicase-in-nuclear-r-loop-metabolism
#20
Dana Hodroj, Bénédicte Recolin, Kamar Serhal, Susan Martinez, Nikolay Tsanov, Raghida Abou Merhi, Domenico Maiorano
Coordination between transcription and replication is crucial in the maintenance of genome integrity. Disturbance of these processes leads to accumulation of aberrant DNA:RNA hybrids (R-loops) that, if unresolved, generate DNA damage and genomic instability. Here we report a novel, unexpected role for the nucleopore-associated mRNA export factor Ddx19 in removing nuclear R-loops formed upon replication stress or DNA damage. We show, in live cells, that Ddx19 transiently relocalizes from the nucleopore to the nucleus upon DNA damage, in an ATR/Chk1-dependent manner, and that Ddx19 nuclear relocalization is required to clear R-loops...
May 2, 2017: EMBO Journal
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