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Crispr-Cas

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https://www.readbyqxmd.com/read/28441427/programmable-type-iii-a-crispr-cas-dna-targeting-modules
#1
H Travis Ichikawa, John C Cooper, Leja Lo, Jason Potter, Rebecca M Terns, Michael P Terns
The CRISPR-Cas systems provide invader defense in a wide variety of prokaryotes, as well as technologies for many powerful applications. The Type III-A or Csm CRISPR-Cas system is one of the most widely distributed across prokaryotic phyla, and cleaves targeted DNA and RNA molecules. In this work, we have constructed modules of Csm systems from 3 bacterial species and heterologously expressed the functional modules in E. coli. The modules include a Cas6 protein and a CRISPR locus for crRNA production, and Csm effector complex proteins...
2017: PloS One
https://www.readbyqxmd.com/read/28439853/crispr-cas-mediated-in-planta-gene-targeting
#2
Simon Schiml, Friedrich Fauser, Holger Puchta
The recent emergence of the CRISPR/Cas system has boosted the possibilities for precise genome engineering approaches throughout all kingdoms of life. The most common application for plants is targeted mutagenesis, whereby a Cas9-mediated DNA double-strand break (DSB) is repaired by mutagenic nonhomologous end joining (NHEJ). However, the site-specific alteration of a genomic sequence or integration of a transgene relies on the precise repair by homologous recombination (HR) using a suitable donor sequence: this poses a particular challenge in plants, as NHEJ is the preferred repair mechanism for DSBs in somatic tissue...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28438939/emergence-and-evolution-of-multidrug-resistant-klebsiella-pneumoniae-with-both-blakpc-and-blactx-m-integrated-in-chromosome
#3
Weihua Huang, Guiqing Wang, Robert Sebra, Jian Zhuge, Changhong Yin, Maria E Aguero-Rosenfeld, Audrey N Schuetz, Nevenka Dimitrova, John T Fallon
The extended-spectrum β-lactamase (ESBL)- and Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae represent serious and urgent threats to public health. In a retrospective study of multidrug-resistant K. pneumoniae, we identified three clinical isolates, CN1, CR14 and NY9, carrying both blaCTX-M and blaKPC genes. The complete genomes of these three K. pneumoniae isolates were de novo assembled by using both short- and long-read whole-genome sequencing. In CR14 and NY9, blaCTX-M and blaKPC were carried on two different plasmids...
April 24, 2017: Antimicrobial Agents and Chemotherapy
https://www.readbyqxmd.com/read/28438299/can-gene-editing-and-silencing-technologies-play-a-role-in-the-treatment-of-head-and-neck-cancer
#4
REVIEW
Mushfiq H Shaikh, Daniel T W Clarke, Newell W Johnson, Nigel A J McMillan
Conventional treatment strategies have done little to improve the prognosis or disease-free survival in head and neck cancer (HNC) patients. Recent progress in our understanding of molecular aspects of head and neck squamous cell carcinoma (HNSCC) has provided insights into the potential use of molecular targeted therapies in combination with current treatment strategies. Here we review the current understanding of treatment modalities for both HPV-positive and HPV-negative HNSCCs with the potential to use gene editing and silencing technologies therapeutically...
May 2017: Oral Oncology
https://www.readbyqxmd.com/read/28438207/large-scale-validation-of-an-efficient-crispr-cas-based-multi-gene-editing-protocol-in-escherichia-coli
#5
Francesca Zerbini, Ilaria Zanella, Davide Fraccascia, Enrico König, Carmela Irene, Luca F Frattini, Michele Tomasi, Laura Fantappiè, Luisa Ganfini, Elena Caproni, Matteo Parri, Alberto Grandi, Guido Grandi
BACKGROUND: The exploitation of the CRISPR/Cas9 machinery coupled to lambda (λ) recombinase-mediated homologous recombination (recombineering) is becoming the method of choice for genome editing in E. coli. First proposed by Jiang and co-workers, the strategy has been subsequently fine-tuned by several authors who demonstrated, by using few selected loci, that the efficiency of mutagenesis (number of mutant colonies over total number of colonies analyzed) can be extremely high (up to 100%)...
April 24, 2017: Microbial Cell Factories
https://www.readbyqxmd.com/read/28435892/dramatic-improvement-of-crispr-cas9-editing-in-candida-albicans-by-increased-single-guide-rna-expression
#6
Henry Ng, Neta Dean
The clustered regularly interspaced short palindromic repeat system with CRISPR-associated protein 9 nuclease (CRISPR/Cas9) has emerged as a versatile tool for genome editing in Candida albicans. Mounting evidence from other model systems suggests that the intracellular levels of single guide RNA (sgRNA) limit the efficiency of Cas9-dependent DNA cleavage. Here, we tested this idea and describe a new means of sgRNA delivery that improves previously described methods by ~10-fold. The efficiency of Cas9/sgRNA-dependent cleavage and repair of a single-copy yeast enhanced monomeric red fluorescent protein (RFP) gene was measured as a function of various parameters that are hypothesized to affect sgRNA accumulation, including transcriptional and posttranscriptional processing...
March 2017: MSphere
https://www.readbyqxmd.com/read/28431233/a-compendium-of-rna-binding-proteins-that-regulate-microrna-biogenesis
#7
Thomas Treiber, Nora Treiber, Uwe Plessmann, Simone Harlander, Julia-Lisa Daiß, Norbert Eichner, Gerhard Lehmann, Kevin Schall, Henning Urlaub, Gunter Meister
During microRNA (miRNA) biogenesis, two endonucleolytic reactions convert stem-loop-structured precursors into mature miRNAs. These processing steps can be posttranscriptionally regulated by RNA-binding proteins (RBPs). Here, we have used a proteomics-based pull-down approach to map and characterize the interactome of a multitude of pre-miRNAs. We identify ∼180 RBPs that interact specifically with distinct pre-miRNAs. For functional validation, we combined RNAi and CRISPR/Cas-mediated knockout experiments to analyze RBP-dependent changes in miRNA levels...
April 20, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28430356/crispr-cas9-an-rna-guided-highly-precise-synthetic-tool-for-plant-genome-editing
#8
REVIEW
Yeliz Demirci, Baohong Zhang, Turgay Unver
CRISPR/Cas 9 is a newly developed and naturally occurred genome editing tool, which is originally used by bacteria for immune defence. In the past years, it has been quickly employed and modified to precisely edit genome sequences in both plants and animals. Compared with the well-developed zinc finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs), CRISPR/Cas 9 has lots of advantages, including easier to design and implement, higher targeting efficiency, and less expensive. Thus, it is becoming one of the most powerful tools for knockout of an individual gene as well as insertion of one gene and/or control of gene transcription...
April 21, 2017: Journal of Cellular Physiology
https://www.readbyqxmd.com/read/28427330/pan-genome-and-crispr-analyses-of-the-bacterial-fish-pathogen-moritella-viscosa
#9
Christian Karlsen, Erik Hjerde, Terje Klemetsen, Nils Peder Willassen
BACKGROUND: Winter-ulcer Moritella viscosa infections continue to be a significant burden in Atlantic salmon (Salmo salar L.) farming. M. viscosa comprises two main clusters that differ in genetic variation and phenotypes including virulence. Horizontal gene transfer through acquisition and loss of mobile genetic elements (MGEs) is a major driving force of bacterial diversification. To gain insight into genomic traits that could affect sublineage evolution within this bacterium we examined the genome sequences of twelve M...
April 20, 2017: BMC Genomics
https://www.readbyqxmd.com/read/28426329/mathematical-modelling-of-crispr-cas-system-effects-on-biofilm-formation
#10
Qasim Ali, Lindi M Wahl
Clustered regularly interspaced short palindromic repeats (CRISPR), linked with CRISPR associated (Cas) genes, can confer adaptive immunity to bacteria, against bacteriophage infections. Thus from a therapeutic standpoint, CRISPR immunity increases biofilm resistance to phage therapy. Recently, however, CRISPR-Cas genes have been implicated in reducing biofilm formation in lysogenized cells. Thus CRISPR immunity can have complex effects on phage-host-lysogen interactions, particularly in a biofilm. In this contribution, we develop and analyse a series of dynamical systems to elucidate and disentangle these interactions...
April 20, 2017: Journal of Biological Dynamics
https://www.readbyqxmd.com/read/28426191/genome-wide-abolishment-of-mobile-genetic-elements-using-genome-shuffling-and-crispr-cas-assisted-mage-allows-the-efficient-stabilization-of-a-bacterial-chassis
#11
Kinga Umenhoffer, Gábor Draskovits, Ákos Nyerges, Ildikó Karcagi, Balázs Bogos, Edit Tímár, Bálint Csörgő, Róbert Herczeg, István Nagy, Tamás Fehér, Csaba Pal, Gyorgy Posfai
The ideal bacterial chassis provides a simplified, stable and predictable host environment for synthetic biological circuits. Mutability and evolution can, however, compromise stability, leading to deterioration of artificial genetic constructs. By eliminating certain sources of instability, these undesired genetic changes can be mitigated. Specifically, deletion of prophages and insertion sequences, non-essential constituents of bacterial genomes, has been shown to be beneficial in cellular and genetic stabilization...
April 20, 2017: ACS Synthetic Biology
https://www.readbyqxmd.com/read/28422737/generation-of-lung-cancer-cell-lines-harboring-egfr-t790m-mutation-by-crispr-cas9-mediated-genome-editing
#12
Mi-Young Park, Min Hee Jung, Eun Young Eo, Seokjoong Kim, Sang Hoon Lee, Yeon Joo Lee, Jong Sun Park, Young Jae Cho, Jin Haeng Chung, Cheol Hyeon Kim, Ho Il Yoon, Jae Ho Lee, Choon-Taek Lee
Tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib are effective against lung adenocarcinomas harboring epidermal growth factor receptor (EGFR) mutations. However, cancer cells can develop resistance to these agents with prolonged exposure; in over 50% of cases, this is attributable to the EGFR T790M mutation. Moreover, additional resistance mutations can arise with the use of new drugs. Cancer cell lines with specific mutations can enable the study of resistance mechanisms. In this study, we introduced the EGFR T790M mutation into the PC9 human lung cancer cell line-which has a deletion in exon 19 of the EGFR gene-by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas)9-mediated genome editing...
March 31, 2017: Oncotarget
https://www.readbyqxmd.com/read/28420884/a-crispr-toolbox-to-study-virus-host-interactions
#13
REVIEW
Andreas S Puschnik, Karim Majzoub, Yaw Shin Ooi, Jan E Carette
Viruses depend on their hosts to complete their replication cycles; they exploit cellular receptors for entry and hijack cellular functions to replicate their genome, assemble progeny virions and spread. Recently, genome-scale CRISPR-Cas screens have been used to identify host factors that are required for virus replication, including the replication of clinically relevant viruses such as Zika virus, West Nile virus, dengue virus and hepatitis C virus. In this Review, we discuss the technical aspects of genome-scale knockout screens using CRISPR-Cas technology, and we compare these screens with alternative genetic screening technologies...
April 19, 2017: Nature Reviews. Microbiology
https://www.readbyqxmd.com/read/28410976/genome-editing-via-delivery-of-cas9-ribonucleoprotein
#14
Mark DeWitt, Jacob E Corn, Dana Carroll
The CRISPR-Cas genome editing system is very powerful. The format of the CRISPR reagents and the means of delivery are often important factors in targeting efficiency. Delivery of recombinant Cas9 protein and guide RNA (gRNA) as a preformed ribonucleoprotein (RNP) complex has recently emerged as a powerful and general approach to genome editing. Here we outline methods to produce and deliver Cas9 RNPs. A donor DNA carrying desired sequence changes can also be included to program precise sequence introduction or replacement...
April 11, 2017: Methods: a Companion to Methods in Enzymology
https://www.readbyqxmd.com/read/28392985/conserved-dna-motifs-in-the-type-ii-a-crispr-leader-region
#15
Mason J Van Orden, Peter Klein, Kesavan Babu, Fares Z Najar, Rakhi Rajan
The Clustered Regularly Interspaced Short Palindromic Repeats associated (CRISPR-Cas) systems consist of RNA-protein complexes that provide bacteria and archaea with sequence-specific immunity against bacteriophages, plasmids, and other mobile genetic elements. Bacteria and archaea become immune to phage or plasmid infections by inserting short pieces of the intruder DNA (spacer) site-specifically into the leader-repeat junction in a process called adaptation. Previous studies have shown that parts of the leader region, especially the 3' end of the leader, are indispensable for adaptation...
2017: PeerJ
https://www.readbyqxmd.com/read/28391963/finally-archaea-get-their-crispr-cas-toolbox
#16
Uri Gophna, Thorsten Allers, Anita Marchfelder
The majority of archaea encode CRISPR-Cas systems but only a few CRISPR-Cas-based genetic tools have been developed for organisms from this domain. Nayak and Metcalf have harnessed a bacterial Cas9 protein for genome editing in Methanosarcina acetivorans, enabling efficient gene deletion and replacement.
April 5, 2017: Trends in Microbiology
https://www.readbyqxmd.com/read/28388605/refining-strategies-to-translate-genome-editing-to-the-clinic
#17
REVIEW
Tatjana I Cornu, Claudio Mussolino, Toni Cathomen
Recent progress in developing programmable nucleases, such as zinc-finger nucleases, transcription activator-like effector nucleases (TALENs) and clustered regularly interspaced short palindromic repeat (CRISPR)-Cas nucleases, have paved the way for gene editing to enter clinical practice. This translation is a result of combining high nuclease activity with high specificity and successfully applying this technology in various preclinical disease models, including infectious disease, primary immunodeficiencies, hemoglobinopathies, hemophilia and muscular dystrophy...
April 3, 2017: Nature Medicine
https://www.readbyqxmd.com/read/28387220/targeted-activation-of-diverse-crispr-cas-systems-for-mammalian-genome-editing-via-proximal-crispr-targeting
#18
Fuqiang Chen, Xiao Ding, Yongmei Feng, Timothy Seebeck, Yanfang Jiang, Gregory D Davis
Bacterial CRISPR-Cas systems comprise diverse effector endonucleases with different targeting ranges, specificities and enzymatic properties, but many of them are inactive in mammalian cells and are thus precluded from genome-editing applications. Here we show that the type II-B FnCas9 from Francisella novicida possesses novel properties, but its nuclease function is frequently inhibited at many genomic loci in living human cells. Moreover, we develop a proximal CRISPR (termed proxy-CRISPR) targeting method that restores FnCas9 nuclease activity in a target-specific manner...
April 7, 2017: Nature Communications
https://www.readbyqxmd.com/read/28386301/new-traits-in-crops-produced-by-genome-editing-techniques-based-on-deletions
#19
REVIEW
C C M van de Wiel, J G Schaart, L A P Lotz, M J M Smulders
One of the most promising New Plant Breeding Techniques is genome editing (also called gene editing) with the help of a programmable site-directed nuclease (SDN). In this review, we focus on SDN-1, which is the generation of small deletions or insertions (indels) at a precisely defined location in the genome with zinc finger nucleases (ZFN), TALENs, or CRISPR-Cas9. The programmable nuclease is used to induce a double-strand break in the DNA, while the repair is left to the plant cell itself, and mistakes are introduced, while the cell is repairing the double-strand break using the relatively error-prone NHEJ pathway...
2017: Plant Biotechnology Reports
https://www.readbyqxmd.com/read/28385959/crispr-cas-adapting-to-change
#20
REVIEW
Simon A Jackson, Rebecca E McKenzie, Robert D Fagerlund, Sebastian N Kieper, Peter C Fineran, Stan J J Brouns
Bacteria and archaea are engaged in a constant arms race to defend against the ever-present threats of viruses and invasion by mobile genetic elements. The most flexible weapons in the prokaryotic defense arsenal are the CRISPR-Cas adaptive immune systems. These systems are capable of selective identification and neutralization of foreign DNA and/or RNA. CRISPR-Cas systems rely on stored genetic memories to facilitate target recognition. Thus, to keep pace with a changing pool of hostile invaders, the CRISPR memory banks must be regularly updated with new information through a process termed CRISPR adaptation...
April 7, 2017: Science
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