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Methods in Enzymology

Scott Bailey
No abstract text is available yet for this article.
2019: Methods in Enzymology
Angela Patterson, Monika Tokmina-Lukaszewska, Brian Bothner
Adaptive prokaryotic immune systems rely on clustered regularly interspaced short palindromic repeats and their associated genes to provide the components necessary to clear infection by foreign genetic elements. These immune systems are based on highly specific nucleases that bind DNA or RNA and, upon sequence recognition, degrade the bound nucleic acid. Because of their specificity, CRISPR-Cas systems are being co-opted to edit genes in eukaryotic cells. While the general function of these systems is well understood, an understanding of mechanistic details to facilitate engineering and application to this new arena remains a topic of intense study...
2019: Methods in Enzymology
Phong T Phan, Michael Schelling, Chaoyou Xue, Dipali G Sashital
Type I, II, and V CRISPR-Cas systems are RNA-guided dsDNA targeting defense mechanisms found in bacteria and archaea. During CRISPR interference, Cas effectors use CRISPR-derived RNAs (crRNAs) as guides to bind complementary sequences in foreign dsDNA, leading to the cleavage and destruction of the DNA target. Mutations within the target or in the protospacer adjacent motif can reduce the level of CRISPR interference, although the level of defect is dependent on the type and position of the mutation, as well as the guide sequence of the crRNA...
2019: Methods in Enzymology
Kaylee E Dillard, Jeffrey M Schaub, Maxwell W Brown, Fatema A Saifuddin, Yibei Xiao, Erik Hernandez, Samuel D Dahlhauser, Eric V Anslyn, Ailong Ke, Ilya J Finkelstein
Fluorescent labeling of proteins is a critical requirement for single-molecule imaging studies. Many protein labeling strategies require harsh conditions or large epitopes that can inactivate the target protein, either by decreasing the protein's enzymatic activity or by blocking protein-protein interactions. Here, we provide a detailed protocol to efficiently label CRISPR-Cas complexes with a small fluorescent peptide via sortase-mediated transpeptidation. The sortase tag consists of just a few amino acids that are specifically recognized at either the N- or the C-terminus, making this strategy advantageous when the protein is part of a larger complex...
2019: Methods in Enzymology
Robert D Fagerlund, Timothy J Ferguson, Howard W R Maxwell, Helen K Opel-Reading, Kurt L Krause, Peter C Fineran
CRISPR adaptation is the initial step in CRISPR-Cas immunity and involves the acquisition of foreign invading DNA. Acquisition is facilitated by the almost universally conserved proteins Cas1 and Cas2, which form an adaptation complex. The Cas1-Cas2 complex binds fragments of invading DNA, completes final processing, and catalyzes integration into specific host loci called CRISPR arrays. Structural and biochemical studies from reconstituted complexes have provided mechanistic insight into how CRISPR adaptation occurs; however, these studies have been limited to a narrow subset of CRISPR-Cas types and may not be representative of the other types...
2019: Methods in Enzymology
S M Nayeemul Bari, Asma Hatoum-Aslan
Phages are the most abundant entities in the biosphere and profoundly impact the bacterial populations within and around us. They attach to a specific host, inject their DNA, hijack the host's cellular processes, and replicate exponentially while destroying the host. Historically, phages have been exploited as powerful antimicrobials, and phage-derived proteins have constituted the basis for numerous biotechnological applications. Only in recent years have metagenomic studies revealed that phage genomes harbor a rich reservoir of genetic diversity, which might afford further therapeutic and/or biotechnological value...
2019: Methods in Enzymology
Xin D Gao, Tomás C Rodríguez, Erik J Sontheimer
Genome organization and subnuclear protein localization are essential for normal cellular function and have been implicated in the control of gene expression, DNA replication, and genomic stability. The coupling of chromatin conformation capture (3C), chromatin immunoprecipitation and sequencing, and related techniques have continuously improved our understanding of genome architecture. To profile site-specifically DNA-associated proteins in a high-throughput and unbiased manner, the RNA-programmable CRISPR-Cas9 platform has recently been combined with an enzymatic labeling system to allow proteomic landscapes at repetitive and nonrepetitive loci to be defined with unprecedented ease and resolution...
2019: Methods in Enzymology
Vladimir Mekler, Konstantin Kuznedelov, Leonid Minakhin, Karthik Murugan, Dipali G Sashital, Konstantin Severinov
CRISPR-Cas systems protect prokaryotic cells from invading phages and plasmids by recognizing and cleaving foreign nucleic acid sequences specified by CRISPR RNA spacer sequences. Several CRISPR-Cas systems have been widely used as tool for genetic engineering. In DNA-targeting CRISPR-Cas nucleoprotein effector complexes, the CRISPR RNA forms a hybrid with the complementary strand of foreign DNA, displacing the noncomplementary strand to form an R-loop. The DNA interrogation and R-loop formation involve several distinct steps the molecular details of which are not fully understood...
2019: Methods in Enzymology
Viktorija Globyte, Chirlmin Joo
Since its discovery, the CRISPR-Cas9 system has been in the center of attention for its promising applications in genome editing. However, in order to apply this system successfully in genetic engineering, all aspects of its molecular mechanism have to be well understood. One of the best ways to investigate the intricacies of the molecular mechanism is single-molecule studies as they allow real-time observation of the kinetic processes and provide high spatiotemporal resolution. This chapter describes single-molecule fluorescence resonance energy transfer experiments carried out to investigate the Cas9 protein from Streptococcus pyogenes, providing information on the effects of target truncation, Cas9-induced double-stranded DNA dynamics, and target search...
2019: Methods in Enzymology
Mu-Sen Liu, Shanzhong Gong, Helen-Hong Yu, David W Taylor, Kenneth A Johnson
Bacterial adaptive immune systems employ clustered regularly interspaced short palindromic repeats (CRISPR) along with their CRISPR-associated genes (Cas) to form CRISPR RNA (crRNA)-guided surveillance complexes, which target foreign nucleic acids for destruction. Cas9 is unique in that it is composed of a single polypeptide that utilizes both a crRNA and a trans-activating crRNA (tracrRNA) or a single guide RNA to create double-stranded breaks in sequences complementary to the RNA via the HNH and RuvC nuclease domains...
2019: Methods in Enzymology
Yibei Xiao, Ailong Ke
Type I CRISPR-Cas, the most prevalent CRISPR system, features a sequential target searching and degradation process. First, the multisubunit surveillance complex Cascade recognizes the matching dsDNA target flanked by protospacer adjacent motif (PAM), promotes the heteroduplex formation between CRISPR RNA (crRNA) and the target strand (TS) DNA, and displaces the nontarget strand (NTS) DNA, resulting in R-loop formation. The helicase-nuclease fusion enzyme Cas3 is then specifically recruited to Cascade/R-loop, nicks, and processively degrades the DNA target...
2019: Methods in Enzymology
Travis H Hand, Anuska Das, Hong Li
Though making up nearly half of the known CRISPR-Cas9 family of enzymes, the Type II-C CRISPR-Cas9 has been underexplored for their molecular mechanisms and potential in safe gene editing applications. In comparison with the more popular Type II-A CRISPR-Cas9, the Type II-C enzymes are generally smaller in size and utilize longer base pairing in identification of their DNA substrates. These characteristics suggest easier portability and potentially less off-targets for Type II-C in gene editing applications...
2019: Methods in Enzymology
Lucas Kissling, Asun Monfort, Daan C Swarts, Anton Wutz, Martin Jinek
CRISPR-Cas12a is a bacterial RNA-guided deoxyribonuclease that has been adopted for genetic engineering in a broad variety of organisms. Here, we describe protocols for the preparation and application of AsCas12a-guide RNA ribonucleoprotein (RNP) complexes for engineering gene deletions in mouse embryonic stem (ES) cells. We provide detailed protocols for purification of an NLS-containing AsCas12a-eGFP fusion protein, design of guide RNAs, assembly of RNP complexes, and transfection of mouse ES cells by electroporation...
2019: Methods in Enzymology
Tautvydas Karvelis, Joshua K Young, Virginijus Siksnys
In recent years, Cas9 has revolutionized the genome-editing field and enabled a broad range of applications from basic biology to biotechnology and medicine. Cas9 specificity is dictated by base pairing of the guide RNA to the complementary DNA strand, however to initiate hybridization, a short protospacer adjacent motif (PAM) sequence is required in the vicinity of the target sequence. The PAM is recognized by the Cas9 protein and varies between Cas9s. There are thousands of type II CRISPR-Cas9 sequences available in sequence databases...
2019: Methods in Enzymology
Christophe Rouillon, Januka S Athukoralage, Shirley Graham, Sabine Grüschow, Malcolm F White
Type III CRISPR effector complexes utilize a bound CRISPR RNA (crRNA) to detect the presence of RNA from invading mobile genetic elements in the cell. This RNA binding results in the activation of two enzymatic domains of the Cas10 subunit-the HD nuclease domain, which degrades DNA, and PALM/cyclase domain. The latter synthesizes cyclic oligoadenylate (cOA) molecules by polymerizing ATP, and cOA acts as a second messenger in the cell, switching on the antiviral response by activating host ribonucleases and other proteins...
2019: Methods in Enzymology
Kwang-Hyun Park, Yan An, Eui-Jeon Woo
The CRISPR-Cas system is the prokaryotic immune response that destroys invading foreign nucleic acids. Based on the architecture and distinct mechanism of targeting, the CRISPR-Cas system is classified into six types (I-VI). The Csm complex belongs to the type III system and consists of five subunits (Cas10 and Csm2-5) and a crRNA. The Csm complex targets RNA and RNA-dependent single-strand DNA. Here, we present a protocol for in vitro reconstitution of a Csm complex from a hyperthermophilic archaeon Thermococcus onnurineus NA1 (ToCsm complex)...
2019: Methods in Enzymology
Bartosz Turkowyd, Hanna Müller-Esparza, Vanessa Climenti, Niklas Steube, Ulrike Endesfelder, Lennart Randau
Type I CRISPR-Cas systems utilize small CRISPR RNA (crRNA) molecules to scan DNA strands for target regions. Different crRNAs are bound by several CRISPR-associated (Cas) protein subunits that form the stable ribonucleoprotein complex Cascade. The Cascade-mediated DNA surveillance process requires a sufficient degree of base-complementarity between crRNA and target sequences and relies on the recognition of small DNA motifs, termed protospacer adjacent motifs. Recently, super-resolution microscopy and single-particle tracking methods have been developed to follow individual protein complexes in live cells...
2019: Methods in Enzymology
Joseph T Wade
The specificity of CRISPR-Cas systems for nucleic acid targets is determined by a combination of binding and cleavage. Understanding the mechanisms by which Cas proteins specifically select their targets is critical for the development of CRISPR-Cas systems for biotechnology applications. Moreover, the specificity of CRISPR-Cas systems plays an important role in prokaryote evolution due to its role in distinguishing self from nonself. Here, I describe Library-ChIP, a high-throughput method for measuring Cas protein occupancy at many DNA sequence variants in a native prokaryotic host...
2019: Methods in Enzymology
Matthew A Nethery, Rodolphe Barrangou
Pervasive application of CRISPR-Cas systems in genome editing has prompted an increase in both interest and necessity to further elucidate existing systems as well as discover putative novel systems. The ubiquity and power of current computational platforms have made in silico approaches to CRISPR-Cas identification and characterization accessible to a wider audience and increasingly amenable for processing extensive data sets. Here, we describe in silico methods for predicting and visualizing notable features of CRISPR-Cas systems, including Cas domain determination, CRISPR array visualization, and inference of the protospacer-adjacent motif...
2019: Methods in Enzymology
A Joshua Wand
No abstract text is available yet for this article.
2019: Methods in Enzymology
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