This work was supported by NIH grant R01-CA158283 and NSFC grant 31400726 to Z.W. Y.W. is funded by the Young Thousand Talents Program and the National Natural Science Foundation of China (grants 31471235 and 81422038). X.Y. is funded by the postdoctoral science foundation of China (2015M571612).

<ol>
	<li>Wang, E. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alternative+isoform+regulation+in+human+tissue+transcriptomes.">Alternative isoform regulation in human tissue transcriptomes.</a> Nature. 456 (7221), 470-476 (2008).</li><li>Pan, Q., Shai, O., Lee, L. J., Frey, B. J., Blencowe, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deep+surveying+of+alternative+splicing+complexity+in+the+human+transcriptome+by+high-throughput+sequencing.">Deep surveying of alternative splicing complexity in the human transcriptome by high-throughput sequencing.</a> Nat Genet. 40 (12), 1413-1415 (2008).</li><li>Wang, Z., Burge, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Splicing+regulation:+from+a+parts+list+of+regulatory+elements+to+an+integrated+splicing+code.">Splicing regulation: from a parts list of regulatory elements to an integrated splicing code.</a> Rna. 14 (5), 802-813 (2008).</li><li>Matera, A. G., Wang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+day+in+the+life+of+the+spliceosome.">A day in the life of the spliceosome.</a> Nat Rev Mol Cell Biol. 15 (2), 108-121 (2014).</li><li>Singh, R. K., Cooper, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pre-mRNA+splicing+in+disease+and+therapeutics.">Pre-mRNA splicing in disease and therapeutics.</a> Trends Mol Med. 18 (8), 472-482 (2012).</li><li>Wang, G. -. S., Cooper, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Splicing+in+disease:+disruption+of+the+splicing+code+and+the+decoding+machinery.">Splicing in disease: disruption of the splicing code and the decoding machinery.</a> Nat Rev Genet. 8 (10), 749-761 (2007).</li><li>Li, Y. I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+splicing+is+a+primary+link+between+genetic+variation+and+disease.">RNA splicing is a primary link between genetic variation and disease.</a> Science. 352 (6285), 600-604 (2016).</li><li>Scotti, M. M., Swanson, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+mis-splicing+in+disease.">RNA mis-splicing in disease.</a> Nat Rev Genet. 17 (1), 19-32 (2016).</li><li>Black, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+alternative+pre-messenger+RNA+splicing.">Mechanisms of alternative pre-messenger RNA splicing.</a> Annu Rev Biochem. 72 (1), 291-336 (2003).</li><li>Graveley, B. R., Maniatis, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Arginine/serine-rich+domains+of+SR+proteins+can+function+as+activators+of+pre-mRNA+splicing.">Arginine/serine-rich domains of SR proteins can function as activators of pre-mRNA splicing.</a> Mol cell. 1 (5), 765-771 (1998).</li><li>Del Gatto-Konczak, F., Olive, M., Gesnel, M. -. C., Breathnach, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=hnRNP+A1+recruited+to+an+exon+in+vivo+can+function+as+an+exon+splicing+silencer.">hnRNP A1 recruited to an exon in vivo can function as an exon splicing silencer.</a> Mol Cell Biol. 19 (1), 251-260 (1999).</li><li>Auweter, S. D., Oberstrass, F. C., Allain, F. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sequence-specific+binding+of+single-stranded+RNA:+is+there+a+code+for+recognition.">Sequence-specific binding of single-stranded RNA: is there a code for recognition.</a> Nucleic Acids Res. 34 (17), 4943-4959 (2006).</li><li>Dong, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Specific+and+modular+binding+code+for+cytosine+recognition+in+Pumilio/FBF+(PUF)+RNA-binding+domains.">Specific and modular binding code for cytosine recognition in Pumilio/FBF (PUF) RNA-binding domains.</a> J Biol Chem. 286 (30), 26732-26742 (2011).</li><li>Filipovska, A., Razif, M. F., Nyg&#229;rd, K. K., Rackham, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+universal+code+for+RNA+recognition+by+PUF+proteins.">A universal code for RNA recognition by PUF proteins.</a> Nat Chem Biol. 7 (7), 425-427 (2011).</li><li>Wei, H., Wang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+RNA-binding+proteins+with+diverse+activities.">Engineering RNA-binding proteins with diverse activities.</a> Wiley Interdiscip Rev RNA. 6 (6), 597-613 (2015).</li><li>Wang, Y., Cheong, C. -. G., Hall, T. M. T., Wang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+splicing+factors+with+designed+specificities.">Engineering splicing factors with designed specificities.</a> Nat Methods. 6 (11), 825-830 (2009).</li><li>Choudhury, R., Tsai, Y. S., Dominguez, D., Wang, Y., Wang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+RNA+endonucleases+with+customized+sequence+specificities.">Engineering RNA endonucleases with customized sequence specificities.</a> Nat Commun. 3, 1147 (2012).</li><li>Wang, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+complex+network+of+factors+with+overlapping+affinities+represses+splicing+through+intronic+elements.">A complex network of factors with overlapping affinities represses splicing through intronic elements.</a> Nat Struct Mol Biol. 20 (1), 36-45 (2013).</li><li>McCabe, B. C., Gollnick, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+levels+of+trp+RNA-binding+attenuation+protein+in+Bacillus+subtilis.">Cellular levels of trp RNA-binding attenuation protein in Bacillus subtilis.</a> J Bacteriol. 186 (15), 5157-5159 (2004).</li><li>Wang, Y., Ma, M., Xiao, X., Wang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intronic+splicing+enhancers,+cognate+splicing+factors+and+context-dependent+regulation+rules.">Intronic splicing enhancers, cognate splicing factors and context-dependent regulation rules.</a> Nat Struct Mol Biol. 19 (10), 1044-1052 (2012).</li><li>Choudhury, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+splicing+activator+DAZAP1+integrates+splicing+control+into+MEK/Erk-regulated+cell+proliferation+and+migration.">The splicing activator DAZAP1 integrates splicing control into MEK/Erk-regulated cell proliferation and migration.</a> Nat Commun. 5, (2014).</li><li>Xiao, X., Wang, Z., Jang, M., Burge, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coevolutionary+networks+of+splicing+cis-regulatory+elements.">Coevolutionary networks of splicing cis-regulatory elements.</a> Proc Natl Acad Sci U S A. 104 (47), 18583-18588 (2007).</li><li>Wang, Z., Xiao, X., Van Nostrand, E., Burge, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=General+and+specific+functions+of+exonic+splicing+silencers+in+splicing+control.">General and specific functions of exonic splicing silencers in splicing control.</a> Mol Cell. 23 (1), 61-70 (2006).</li><li>Li, M., Husic, N., Lin, Y., Snider, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production+of+lentiviral+vectors+for+transducing+cells+from+the+central+nervous+system.">Production of lentiviral vectors for transducing cells from the central nervous system.</a> J Vis Exp. (63), e4031 (2012).</li><li>Tiscornia, G., Singer, O., Verma, I. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production+and+purification+of+lentiviral+vectors.">Production and purification of lentiviral vectors.</a> Nat Protoc. 1 (1), 241-245 (2006).</li><li>Venables, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aberrant+and+alternative+splicing+in+cancer.">Aberrant and alternative splicing in cancer.</a> Cancer Res. 64 (21), 7647-7654 (2004).</li><li>Cooke, A., Prigge, A., Opperman, L., Wickens, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeted+translational+regulation+using+the+PUF+protein+family+scaffold.">Targeted translational regulation using the PUF protein family scaffold.</a> Proc Natl Acad Sci U S A. 108 (38), 15870-15875 (2011).</li><li>He, C., Zhou, F., Zuo, Z., Cheng, H., Zhou, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+global+view+of+cancer-specific+transcript+variants+by+subtractive+transcriptome-wide+analysis.">A global view of cancer-specific transcript variants by subtractive transcriptome-wide analysis.</a> PloS one. 4 (3), 4732 (2009).</li><li>Venables, J. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+alternative+splicing+markers+for+breast+cancer.">Identification of alternative splicing markers for breast cancer.</a> Cancer Res. 68 (22), 9525-9531 (2008).</li><li>Shapiro, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+EMT-Driven+Alternative+Splicing+Program+Occurs+in+Human+Breast+Cancer.">An EMT-Driven Alternative Splicing Program Occurs in Human Breast Cancer.</a> PLoS Genet. 7 (8), 1002218 (2011).</li><li>David, C. J., Manley, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alternative+pre-mRNA+splicing+regulation+in+cancer:+pathways+and+programs+unhinged.">Alternative pre-mRNA splicing regulation in cancer: pathways and programs unhinged.</a> Genes Dev. 24 (21), 2343-2364 (2010).</li><li>Ladomery, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aberrant+alternative+splicing+is+another+hallmark+of+cancer.">Aberrant alternative splicing is another hallmark of cancer.</a> Int J Cell biol. 2013, (2013).</li><li>Karni, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+gene+encoding+the+splicing+factor+SF2/ASF+is+a+proto-oncogene.">The gene encoding the splicing factor SF2/ASF is a proto-oncogene.</a> Nat Struct Mol Biol. 14 (3), 185-193 (2007).</li><li>Anczuk&#242;w, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SRSF1-regulated+alternative+splicing+in+breast+cancer.">SRSF1-regulated alternative splicing in breast cancer.</a> Mol cell. 60 (1), 105-117 (2015).</li></ol>

The authors have nothing to disclose.

This report provides a detailed description for the design and construction of artificial splicing factors that can specifically manipulate the alternative splicing of a target gene. This method takes advantage of the unique RNA binding mode of PUF repeats to produce an RNA-binding scaffold with customized specificity. It can be used to either activate or repress splicing.
The critical step in this protocol is the generation of the reprogramed PUF domain that defines the specificity of ESFs. A...

Most human genes undergo Alternative Splicing (AS) to produce multiple isoforms with distinct activities, which has greatly increased the coding complexity of the genome1,2. AS provides a major mechanism to regulate gene function, and it is tightly regulated through diverse pathways in different cellular and developmental stages3,4. Because splicing misregulation is a common cause of human disease5,6,7,8, targeting splicing regulation is becoming an attractive therapeutic route.
According to a simplified model of splicing regulation, AS is mainly controlled by Splicing Regulatory cis-Elements (SREs) in pre-mRNA that function as splicing enhancers or silencers of alternative exons. These SREs specifically recruit various trans-acting protein factors (i.e.&#160;splicing factors) that promote or suppress the splicing reaction3,9. Most trans-acting splicing factors have separate sequence-specific RNA binding domains to recognize their targets and effector domains to control splicing. The best-known examples are the members of the serine/arginine-rich (SR) protein family that contain N-terminal RNA Recognition Motifs (RRMs), which bind exonic splicing enhancers, and C-terminal RS domains, which promote exon inclusion10. Conversely, hnRNP A1 binds to exonic splicing silencers through the RRM domains and inhibits exon inclusion through a C-terminal glycine-rich domain11. Using such modular configurations, researchers should be able to engineer artificial splicing factors by combining a specific RNA-Binding Domain (RBD) with different effector domains that activate or inhibit splicing.
The key of such a design is to use an RBD that recognizes given targets with programmable RNA binding specificity, which is analogous to the DNA-binding mode of the TALE domain. However, most native splicing factors contain RRM or K Homology (KH) domains, which recognize short RNA elements with weak affinity and thus lack a predictive RNA-protein recognition &#34;code&#34;12. The RBD of PUF repeat proteins (i.e.&#160;the PUF domain) has a unique RNA recognition mode, allowing for the redesign of PUF domains to specifically recognize different RNA targets13,14. The canonical PUF domain contains eight repeats of three &#945;-helices, each recognizing a single base in an 8-nt RNA target. The side chains of amino acids at certain positions of the second &#945;-helix form specific hydrogen bonds with the Watson-Crick edge of the RNA base, which determines the RNA binding specificity of each repeat (Figure 1A). The code for RNA base recognition of the PUF repeat is surprisingly simple (Figure 1A), allowing for the generation of PUF domains that recognize any possible 8-base combination (reviewed by Wei and Wang15).
This modular design principle allows for the generation of an Engineered Splicing Factor (ESF) that consists of a customized PUF domain and a splicing modulation domain (i.e.&#160;an SR domain or a Gly-rich domain). These ESFs can function as either splicing activators or as inhibitors to control various types of splicing events, and they have proven useful as tools to manipulate the splicing of endogenous genes related to human disease16,17. As an example, we have constructed PUF-Gly-type ESFs to specifically alter the splicing of the Bcl-x gene, converting the anti-apoptotic long isoform (Bcl-xL) to the pro-apoptotic short isoform (Bcl-xS). Shifting the ratio of the Bcl-x isoform was sufficient to sensitize several cancer cells to multiple anti-cancer chemotherapy drugs16, suggesting that these artificial factors may be useful as potential therapeutic reagents.
In addition to controlling splicing with known splicing effector domains (e.g., an RS or Gly-rich domain), the engineered PUF factors can also be used to examine the activities of new splicing factors. For example, using this approach, we have demonstrated that the C-terminal domain of several SR proteins can activate or inhibit splicing when binding to different pre-mRNA regions18, that the alanine-rich motif of RBM4 can inhibit splicing19, and that the proline-rich motif of DAZAP1 can enhance splicing20,21. These new functional domains can be used to construct additional types of artificial factors to fine-tune splicing.

<table><tbody><tr><td>High-fidelity DNA polymerase (Phusion High-Fidelity) with PCR buffer</td><td>New England Biolabs</td><td>M0530L</td><td></td></tr><tr><td>DNA ligase (T4 DNA ligase)</td><td>New England Biolabs</td><td>M0202L</td><td></td></tr><tr><td>Liposomal transfection reagent (Lipofectamine 2000)</td><td>Invitrogen</td><td>11668-019</td><td></td></tr><tr><td>Reduced serum medium (Opti-MEM)</td><td>Gibco</td><td>31985-062</td><td></td></tr><tr><td>RNA extraction buffer (TRIzol Reagent)</td><td>ambion</td><td>15596018</td><td>TRIzol reagent includes phenol, which can cause burns. Wear gloves when handling</td></tr><tr><td>PBS (1x)</td><td>Life Technologies</td><td>10010-031</td><td></td></tr><tr><td>SuperScript III Reverse Transcriptase (RT)</td><td>Invitrogen</td><td>18080044</td><td></td></tr><tr><td>Caspase-3 antibody</td><td>Cell Signaling Technology</td><td>9668</td><td></td></tr><tr><td>PARP antibody</td><td>Cell Signaling Technology</td><td>9542</td><td></td></tr><tr><td>Bcl-x antibody</td><td>BD Bioscience</td><td>610211</td><td></td></tr><tr><td>beta-actin antibody</td><td>Sigma-Aldrich</td><td>A5441</td><td></td></tr><tr><td>alpha-tubulin antibody</td><td>Sigma-Aldrich</td><td>T5168</td><td></td></tr><tr><td>FLAG antibody</td><td>Sigma-Aldrich</td><td>F4042</td><td></td></tr><tr><td>Nitrocellulose membrane</td><td>Amersham-Pharmacia</td><td>RPN203D</td><td></td></tr><tr><td>ECL Western Blotting detection reagents</td><td>Invitrogen</td><td>WP20005</td><td></td></tr><tr><td>Cy5-dCTP</td><td>GE Healthcare</td><td>PA55021</td><td></td></tr><tr><td>Fluorescence-activated Cell Sorter (FACS)</td><td>BD Bioscience</td><td>FACSCalibur&amp;nbsp;</td><td></td></tr><tr><td>Dulbecco&amp;rsquo;s Modified Eagle&amp;rsquo;s Medium (DMEM)</td><td>GE Healthcare</td><td>SH30243.01</td><td></td></tr><tr><td>Fetal Bovine Serum (FBS)</td><td>Invitrogen</td><td>26140079</td><td></td></tr><tr><td>Propidium iodide (PI)</td><td>Sigma</td><td>P4170</td><td></td></tr><tr><td>Bovine Serum Albumin (BSA)</td><td>Sigma</td><td>A7638-5G</td><td></td></tr><tr><td>Triton-X100</td><td>Promega</td><td>H5142</td><td></td></tr><tr><td>Poly-L-Lysine&amp;nbsp;</td><td>Sigma</td><td>P-4832</td><td>Filter-sterilize and store at 4 &amp;deg;C</td></tr><tr><td>Vector pWPXLd</td><td>Addgene</td><td>12258</td><td></td></tr><tr><td>Vector pMD2.G</td><td>Addgene</td><td>12259</td><td></td></tr><tr><td>Vector psPAX2</td><td>Addgene</td><td>12260</td><td></td></tr><tr><td>DNase I (RNase-free)</td><td>New England Biolabs</td><td>M0303S</td><td></td></tr><tr><td>Oligo(dT)&lt;sub&gt;18&lt;/sub&gt; Primer</td><td>Thermo Scientific</td><td>SO131&amp;nbsp;</td><td></td></tr><tr><td>Anti-mouse secondary antibody (Anti-mouse IgG, HRP-linked Antibody)</td><td>Cell Signaling Technology</td><td>7076S</td><td></td></tr></tbody></table>

engineering artificial factors to specifically manipulate alternative splicing in human cells

The processing of most eukaryotic RNAs is mediated by RNA Binding Proteins (RBPs) with modular configurations, including an RNA recognition module, which specifically binds the pre-mRNA target and an effector domain. Previously, we have taken advantage of the unique RNA binding mode of the PUF domain in human Pumilio 1 to generate a programmable RNA binding scaffold, which was used to engineer various artificial RBPs to manipulate RNA metabolism. Here, a detailed protocol is described to construct Engineered Splicing Factors (ESFs) that are specifically designed to modulate the alternative splicing of target genes. The protocol includes how to design and construct a customized PUF scaffold for a specific RNA target, how to construct an ESF expression plasmid by fusing a designer PUF domain and an effector domain, and how to use ESFs to manipulate the splicing of target genes. In the representative results of this method, we have also described the common assays of ESF activities using splicing reporters, the application of ESF in cultured human cells, and the subsequent effect of splicing changes. By following the detailed protocols in this report, it is possible to design and generate ESFs for the regulation of different types of Alternative Splicing (AS), providing a new strategy to study splicing regulation and the function of different splicing isoforms. Moreover, by fusing different functional domains with a designed PUF domain, researchers can engineer artificial factors that target specific RNAs to manipulate various steps of RNA processing.

This report describes the complete protocol for the design and construction of ESFs and splicing reporters. It also outlines the further application of ESFs in manipulating the AS of endogenous genes16. To illustrate typical results of ESF-mediated splicing changes, we use the data from our previous work as an example. The ESFs with different functional domains can be used to promote or inhibit the inclusion of the target cassette exon (Figure ...

Watch this Scientific Journal Video about Engineering Artificial Factors to Specifically Manipulate Alternative Splicing in Human Cells at JoVE.com

Engineering Artificial Factors to Specifically Manipulate Alternative Splicing in Human Cells

This report describes a bioengineering method to design and construct novel Artificial Splicing Factors (ASFs) that specifically modulate the splicing of target genes in mammalian cells. This method can be further expanded to engineer various artificial factors to manipulate other aspects of RNA metabolism.

The processing of most eukaryotic RNAs is mediated by RNA Binding Proteins (RBPs) with modular configurations, including an RNA recognition module, which ...

engineering-artificial-factors-to-specifically-manipulate-alternative

Research

JoVE Journal

Genetics

8.9K Views.  Shanghai Institutes for Biological Sciences (SIBS). This report describes a bioengineering method to design and construct novel Artificial Splicing Factors (ASFs) that specifically modulate the splicing of target genes in mammalian cells. This method can be further expanded to engineer various artificial factors to manipulate other aspects of RNA metabolism.

Video: Engineering Artificial Factors to Specifically Manipulate Alternative Splicing in Human Cells

Using RNA-sequencing to Detect Novel Splice Variants Related to Drug Resistance in In Vitro Cancer Models

Drug resistance remains a major problem in the treatment of cancer for both hematological malignancies and solid tumors. Intrinsic or acquired resistance can be caused by a range of mechanisms, including increased drug elimination, decreased drug uptake, drug inactivation and alterations of drug targets. Recent data showed that other than by well-known genetic (mutation, amplification) and epigenetic (DNA hypermethylation, histone post-translational modification) modifications, drug resistance mechanisms might also be regulated by splicing aberrations. This is a rapidly growing field of investigation that deserves future attention in order to plan more effective therapeutic approaches. The protocol described in this paper is aimed at investigating the impact of aberrant splicing on drug resistance in solid tumors and hematological malignancies. To this goal, we analyzed the transcriptomic profiles of several in vitro models through RNA-seq and established a qRT-PCR based method to validate candidate genes. In particular, we evaluated the differential splicing of DDX5 and PKM transcripts. The aberrant splicing detected by the computational tool MATS was validated in leukemic cells, showing that different DDX5 splice variants are expressed in the parental vs. resistant cells. In these cells, we also observed a higher PKM2/PKM1 ratio, which was not detected in the Panc-1 gemcitabine-resistant counterpart compared to parental Panc-1 cells, suggesting a different mechanism of drug-resistance induced by gemcitabine exposure.

Using RNA-sequencing to Detect Novel Splice Variants Related to Drug Resistance in In Vitro Cancer Models

Here we describe a protocol aimed at investigating the impact of aberrant splicing on drug resistance in solid tumors and hematological malignancies. To this goal, we analyzed the transcriptomic profiles of parental and resistant in vitro models through RNA-seq and established a qRT-PCR based method to validate candidate genes.

Drug resistance remains a major problem in the treatment of cancer for both hematological malignancies and solid tumors. Intrinsic or acquired resistance ...

Cancer Research

Transfection, Selection, and Colony-picking of Human Induced Pluripotent Stem Cells TALEN-targeted with a GFP Gene into the AAVS1 Safe Harbor

Targeted transgene addition can provide persistent gene expression while circumventing the gene silencing and insertional mutagenesis caused by viral vector mediated random integration. This protocol describes a universal and efficient transgene targeted addition platform in human iPSCs based on utilization of validated open-source TALENs and a gene-trap-like donor to deliver transgenes into a safe harbor locus. Importantly, effective gene editing is rate-limited by the delivery efficiency of gene editing vectors. Therefore, this protocol first focuses on preparation of iPSCs for transfection to achieve high nuclear delivery efficiency. When iPSCs are dissociated into single cells using a gentle-cell dissociation reagent and transfected using an optimized program, >50% cells can be induced to take up the large gene editing vectors. Because the AAVS1 locus is located in the intron of an active gene (PPP1R12C), a splicing acceptor (SA)-linked puromycin resistant gene (PAC) was used to select targeted iPSCs while excluding random integration-only and untransfected cells. This strategy greatly increases the chance of obtaining targeted clones, and can be used in other active gene targeting experiments as well. Two weeks after puromycin selection at the dose adjusted for the specific iPSC line, clones are ready to be picked by manual dissection of large, isolated colonies into smaller pieces that are transferred to fresh medium in a smaller well for further expansion and genetic and functional screening. One can follow this protocol to readily obtain multiple GFP reporter iPSC lines that are useful for in vivo and in vitro imaging and cell isolation.

TALEN-mediated gene editing at the safe harbor AAVS1 locus enables high-efficiency transgene addition in human iPSCs. This protocol describes the procedures for preparing iPSCs for TALEN and donor vector delivery, transfecting iPSCs, and selecting and isolating iPSC clones to achieve targeted integration of a GFP gene to generate reporter lines.

Targeted transgene addition can provide persistent gene expression while circumventing the gene silencing and insertional mutagenesis caused by viral ...

Developmental Biology

Quantitative Analysis of Alternative Pre-mRNA Splicing in Mouse Brain Sections Using RNA In Situ Hybridization Assay

Alternative splicing (AS) occurs in more than 90% of human genes. The expression pattern of an alternatively spliced exon is often regulated in a cell type-specific fashion. AS expression patterns are typically analyzed by RT-PCR and RNA-seq using RNA samples isolated from a population of cells. In situ examination of AS expression patterns for a particular biological structure can be carried out by RNA in situ hybridization (ISH) using exon-specific probes. However, this particular use of ISH has been limited because alternative exons are generally too short to design exon-specific probes. In this report, the use of BaseScope, a recently developed technology that employs short antisense oligonucleotides in RNA ISH, is described to analyze AS expression patterns in mouse brain sections. Exon 23a of neurofibromatosis type 1 (Nf1) is used as an example to illustrate that short exon-exon junction probes exhibit robust hybridization signals with high specificity in RNA ISH analysis on mouse brain sections. More importantly, signals detected with exon inclusion- and skipping-specific probes can be used to reliably calculate the percent spliced in values of Nf1 exon 23a expression in different anatomical areas of a mouse brain. The experimental protocol and calculation method for AS analysis are presented. The results indicate that BaseScope provides a powerful new tool to assess AS expression patterns in situ.

Quantitative Analysis of Alternative Pre-mRNA Splicing in Mouse Brain Sections Using RNA In Situ Hybridization Assay

An in situ hybridization (ISH) protocol that uses short antisense oligonucleotides to detect alternative pre-mRNA splicing patterns in mouse brain sections is described.

Alternative splicing (AS) occurs in more than 90% of human genes. The expression pattern of an alternatively spliced exon is often regulated in a cell ...

Use of Alu Element Containing Minigenes to Analyze Circular RNAs

In addition to linear mRNAs, many eukaryotic genes generate circular RNAs. Most circular RNAs are generated by joining a 5&#39; splice site with an upstream 3&#39; splice site within a pre-mRNA, a process called back-splicing. This circularization is likely aided by secondary structures in the pre-mRNA that bring the splice sites into close proximity. In human genes, Alu elements are thought to promote these secondary RNA structures, as Alu elements are abundant and exhibit base complementarities with each other when present in opposite directions in the pre-mRNA. Here, we describe the generation and analysis of large, Alu element containing reporter genes that form circular RNAs. Through optimization of cloning protocols, reporter genes with up to 20 kb insert length can be generated. Their analysis in co-transfection experiments allows the identification of regulatory factors. Thus, this method can identify RNA sequences and cellular components involved in circular RNA formation.

Use of Alu Element Containing Minigenes to Analyze Circular RNAs

We clone and analyze reporter genes generating circular RNAs. These reporter genes are larger than constructs to analyze linear splicing and contain Alu elements. To investigate the circular RNAs, the constructs are transfected into cells and resulting RNA is analyzed using RT-PCR after removal of linear RNA.

In addition to linear mRNAs, many eukaryotic genes generate circular RNAs. Most circular RNAs are generated by joining a 5&#39; splice site with an ...

Biochemistry

Using the E1A Minigene Tool to Study mRNA Splicing Changes

mRNA processing involves multiple simultaneous steps to prepare mRNA for translation, such as 5&#180;capping, poly-A addition and splicing. Besides constitutive splicing, alternative mRNA splicing allows the expression of multifunctional proteins from one gene. As interactome studies are generally the first analysis for new or unknown proteins, the association of the bait protein with splicing factors is an indication that it can participate in mRNA splicing process, but to determine in what context or what genes are regulated is an empirical process. A good starting point to evaluate this function is using the classical minigene tool. Here we present the adenoviral E1A minigene usage for evaluating the alternative splicing changes after different cellular stress stimuli. We evaluated the splicing of E1A minigene in HEK293 stably overexpressing Nek4 protein after different stressing treatments. The protocol includes E1A minigene transfection, cell treatment, RNA extraction and cDNA synthesis, followed by PCR and gel analysis and quantification of the E1A spliced variants. The use of this simple and well-established method combined with specific treatments is a reliable starting point to shed light on cellular processes or what genes can be regulated by mRNA splicing.

This protocol presents a rapid and useful tool for evaluating the role of a protein with uncharacterized function in alternative splicing regulation after chemotherapeutic treatment.

mRNA processing involves multiple simultaneous steps to prepare mRNA for translation, such as 5&#180;capping, poly-A addition and splicing. Besides ...

A Reporter Based Cellular Assay for Monitoring Splicing Efficiency

During gene expression, the vital step of pre-mRNA splicing involves accurate recognition of splice sites and efficient assembly of spliceosomal complexes to join exons and remove introns prior to cytoplasmic export of the mature mRNA. Splicing efficiency can be altered by the presence of mutations at splice sites, the influence of trans-acting splicing factors, or the activity of therapeutics. Here, we describe the protocol for a cellular assay that can be applied for monitoring the splicing efficiency of any given exon. The assay uses an adaptable plasmid encoded 3-exon/2-intron minigene reporter, which can be expressed in mammalian cells by transient transfection. Post-transfection, total cellular RNA is isolated, and the efficiency of exon splicing in the reporter mRNA is determined by either primer extension or semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). We describe how the impact of disease associated 5&#8242; splice-site mutations can be determined by introducing them in the reporter; and how the suppression of these mutations can be achieved by co-transfection with U1 small nuclear RNA (snRNA) construct carrying compensatory mutations in its 5&#8242; region that basepairs with the 5&#8242;-splice sites at exon-intron junctions in pre-mRNAs. Thus, the reporter can be used for the design of therapeutic U1 particles to improve recognition of mutant 5&#8242; splice-sites. Insertion of cis-acting&#160;regulatory sites, such as splicing enhancer or silencer sequences, into the reporter can also be used to examine the role of U1 snRNP in regulation mediated by a specific alternative splicing factor. Finally, reporter expressing cells can be incubated with small molecules to determine the effect of potential therapeutics on constitutive pre-mRNA splicing or on exons carrying mutant 5&#8242; splice sites. Overall, the reporter assay can be applied to monitor splicing efficiency in a variety of conditions to study fundamental splicing mechanisms and splicing-associated diseases.

This protocol describes a minigene reporter assay to monitor the impact of 5&#180;-splice site mutations on splicing and develops suppressor U1 snRNA for the rescue of mutation-induced splicing inhibition. The reporter and suppressor U1 snRNA constructs are expressed in HeLa cells, and splicing is analyzed by primer extension or RT-PCR.

During gene expression, the vital step of pre-mRNA splicing involves accurate recognition of splice sites and efficient assembly of spliceosomal complexes ...

Small-scale Nuclear Extracts for Functional Assays of Gene-expression Machineries

A great deal of progress in understanding gene expression has been made using in vitro systems. For most studies, functional assays are carried out using extracts that are prepared in bulk from 10-50 or more liters of cells grown in suspension. However, these large-scale preparations are not amenable to rapidly testing in vitro effects that result from a variety of in vivo cellular treatments or conditions. This journal video article shows a method for preparing functional small-scale nuclear extracts, using HeLa cells as an example. This method is carried out using as few as three 150 mm plates of cells grown as adherent monolayers. To illustrate the efficiency of the small-scale extracts, we show that they are as active as bulk nuclear extracts for coupled RNA Polymerase II transcription/splicing reactions. To demonstrate the utility of the extract protocol, we show that splicing is abolished in extracts prepared from HeLa cells treated with the splicing inhibitor drug E7107. The small-scale protocol should be generally applicable to any process or cell type that can be investigated in vitro using cellular extracts. These include patient cells that are only available in limited quantities or cells exposed to numerous agents such as drugs, DNA damaging agents, RNAi, or transfection, which require the use of small cell populations. In addition, small amounts of freshly grown cells are convenient and/or required for some applications.

A protocol for preparation of robust, small-scale HeLa nuclear extracts is described. This protocol is valuable for assays that require use of small populations of cells, such as cells treated with drugs or RNAi. The method should be applicable to a wide variety of gene expression assays and other cell types, including patient cells.

A great deal of progress in understanding gene expression has been made using in vitro systems.  For most studies, functional assays are carried out using ...

Biology

Detection of Alternative Splicing During Epithelial-Mesenchymal Transition

Alternative splicing plays a critical role in the epithelial-mesenchymal transition (EMT), an essential cellular program that occurs in various physiological and pathological processes. Here we describe a strategy to detect alternative splicing during EMT using an inducible EMT model by expressing the transcription repressor Twist. EMT is monitored by changes in cell morphology, loss of E-cadherin localization at cell-cell junctions, and the switched expression of EMT markers, such as loss of epithelial markers E-cadherin and &#947;-catenin and gain of mesenchymal markers N-cadherin and vimentin. Using isoform-specific primer sets, the alternative splicing of interested mRNAs are analyzed by quantitative RT-PCR. The production of corresponding protein isoforms is validated by immunoblotting assays. The method of detecting splice isoforms described here is also suitable for the study of alternative splicing in other biological processes.

Alternative splicing regulation has been shown to contribute to the epithelial-mesenchymal transition (EMT), an essential cellular program in various physiological and pathological processes. Here we describe a method utilizing an inducible EMT model for the detection of alternative splicing during EMT.

Alternative splicing plays a critical role in the epithelial-mesenchymal transition (EMT), an essential cellular program that occurs in various ...

Identification of Alternative Splicing and Polyadenylation in RNA-seq Data

As well as the typical analysis of RNA-Seq to measure differential gene expression (DGE) across experimental/biological conditions, RNA-seq data can also be utilized to explore other complex regulatory mechanisms at the exon level. Alternative splicing and polyadenylation play a crucial role in the functional diversity of a gene by generating different isoforms to regulate gene expression at the post-transcriptional level, and limiting analyses to the whole gene level can miss this important regulatory layer. Here, we demonstrate detailed step by step analyses for identification and visualization of differential exon and polyadenylation site usage across conditions, using Bioconductor and other packages and functions, including DEXSeq, diffSplice from the Limma package, and rMATS.

Alternative splicing (AS) and alternative polyadenylation (APA) expand the diversity of transcript isoforms and their products. Here, we describe bioinformatic protocols to analyze bulk RNA-seq and 3' end sequencing assays to detect and visualize AS and APA varying across experimental conditions.

As well as the typical analysis of RNA-Seq to measure differential gene expression (DGE) across experimental/biological conditions, RNA-seq data can also ...

RNA Splicing

Splicing is the process by which eukaryotic RNA is edited before its translation into protein. The RNA strand transcribed from eukaryotic DNA is called the primary transcript. The primary transcripts that become mRNAs are called precursor messenger RNAs (pre-mRNAs). Eukaryotic pre-mRNA contains alternating sequences of exons and introns. Exons are nucleotide sequences that code for proteins, whereas introns are the non-coding regions. In RNA splicing, introns are removed and exons are bonded together.
Splicing is Mediated by the Spliceosome
Splicing occurs in the nucleosome and is mediated by a complex of proteins and small RNAs called small nuclear ribonucleoproteins (snRNPs). snRNPs, together with other proteins, form the spliceosome, which recognizes specific nucleotide sequences at the ends of the exon and intron. First, it binds to a GU-containing sequence at the 5&#39; end of the intron and to a branch point sequence containing an A towards the 3&#39; end of the intron. In a number of carefully-orchestrated steps, other snRNPs then bring the branch point close to the 5&#39; splice site. Subsequently, a chemical reaction cleaves the 5&#39; end of the intron from its upstream exon and attaches it to the branch point, forming a loop called a lariat. To release the lariat, the AG-containing sequence of the intron near the 5&#39; end of the downstream exon reacts with the 3&#39; end of the upstream exon. This reaction patches the two exons together, concluding the splicing process.
Splicing Allows the Expression of Several Proteins from a Single Gene
Typically, exons are joined together in the order in which they appear in a gene. However, during alternative splicing, different combinations of exons in pre-mRNA are combined to form mature mRNA. This produces several different proteins from a single pre-mRNA transcript.
Different patterns of alternative splicing include exon skipping, alternative 5&#39; or 3&#39; splice sites, and intron retention. These patterns are guided by the length of exons or introns and the strength of the splicing signal at the splice sites. Because of this, exons that are shorter than other exons may be overlooked by the spliceosome and omitted from the mature mRNA. In contrast, introns that are significantly shorter than other introns may evade removal by the spliceosome and are retained in the mature mRNA. As a result, alternative splicing generates variants of mature mRNA that were copied from the same stretch of DNA. The RNA sequence variants produce different proteins with additional or fewer amino acids, shifts in the reading frame, or a premature stop codon. These protein isoforms have different biological properties, including function, cellular localization, and interaction with other proteins, thereby playing a vital role in tissue- and environment-specific gene expression.
Abnormal Splicing Can Cause Diseases
Errors in splicing can produce aberrant protein isoforms, which may contribute to diseases, including cancer. For instance, alternative splicing of the BCL2L1 gene generates a long and short protein isoform&#8212;BCL-XL and BCL-XS, respectively&#8212; through the use of alternative 5&#39; splice sites. The longer BCL-XL isoform promotes cell survival and is highly expressed in several types of cancers (e.g., blood, breast, and liver cancers). Expression of the short BCL-XS isoform that promotes cell death is suppressed in cancer.

RNA Splicing, Lariat and the Spliceososme

Splicing is the process by which eukaryotic RNA is edited before its translation into protein. The RNA strand transcribed from eukaryotic DNA is called ...

Engineering Artificial Factors to Specifically Manipulate Alternative Splicing in Human Cells

Summary

Explore More Videos

Chapters in this video

Using RNA-sequencing to Detect Novel Splice Variants Related to Drug Resistance in In Vitro Cancer Models

Transfection, Selection, and Colony-picking of Human Induced Pluripotent Stem Cells TALEN-targeted with a GFP Gene into the AAVS1 Safe Harbor

Quantitative Analysis of Alternative Pre-mRNA Splicing in Mouse Brain Sections Using RNA In Situ Hybridization Assay

Use of Alu Element Containing Minigenes to Analyze Circular RNAs

Using the E1A Minigene Tool to Study mRNA Splicing Changes

A Reporter Based Cellular Assay for Monitoring Splicing Efficiency

Small-scale Nuclear Extracts for Functional Assays of Gene-expression Machineries

Detection of Alternative Splicing During Epithelial-Mesenchymal Transition

Identification of Alternative Splicing and Polyadenylation in RNA-seq Data

RNA Splicing