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).

1. Construction of a PUF Scaffold with Customized RNA-binding Specificity by Overlapping PCR
<ol>
	<li>Design a series of PCR primers containing the PUF sequences that specifically recognize different RNA nucleotides in each position12 (see Table 1 for the primer sequences and see Figure 1A for the RNA:PUF recognition code). For each PUF repeat, design four different primers to recognize a different base on each position. 
	NOT...

<ol>
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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>

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 border="0" cellpadding="0" cellspacing="0" width="1166">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:420px;">High-fidelity DNA polymerase (Phusion High-Fidelity) with PCR buffer</td>
			<td style="width:155px;">New England Biolabs</td>
			<td style="width:103px;">M0530L</td>
			<td style="width:491px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DNA ligase (T4 DNA ligase)</td>
			<td>New England Biolabs</td>
			<td>M0202L</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Liposomal transfection reagent (Lipofectamine 2000)</td>
			<td>Invitrogen</td>
			<td>11668-019</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Reduced serum medium (Opti-MEM)</td>
			<td>Gibco</td>
			<td>31985-062</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">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 height="21">
			<td height="21" style="height:21px;">BSA (Bovine Serum Albumin)</td>
			<td>Sigma-Aldrich</td>
			<td>A7638-5G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PBS (1X)</td>
			<td>Life Technologies</td>
			<td>10010-031</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SuperScript III reverse transcriptase</td>
			<td>Invitrogen</td>
			<td>18080044</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Caspase-3 antibody</td>
			<td>Cell Signaling Technology</td>
			<td>9668</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PARP&#160;antibody</td>
			<td>Cell Signaling Technology</td>
			<td>9542</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Bcl-x antibody</td>
			<td>BD Bioscience</td>
			<td>610211</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">beta-actin antibody</td>
			<td>Sigma-Aldrich</td>
			<td>A5441</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">alpha-tubulin antibody</td>
			<td>Sigma-Aldrich</td>
			<td>T5168</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">FLAG antibody</td>
			<td>Sigma-Aldrich</td>
			<td>F4042</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nitrocellulose membrane</td>
			<td>Amersham-Pharmacia</td>
			<td>RPN203D</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ECL Western Blotting detection reagents</td>
			<td>Invitrogen</td>
			<td>WP20005</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cy5-dCTP</td>
			<td>GE Healthcare</td>
			<td>PA55021</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fluorescence-activated cell sorter</td>
			<td>BD Bioscience</td>
			<td>FACSCalibur&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dulbecco&#8217;s Modified Eagle&#8217;s Medium (DMEM)</td>
			<td>GE Healthcare</td>
			<td>SH30243.01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fetal bovine serum</td>
			<td>Invitrogen</td>
			<td>26140079</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Propidium iodide (PI)</td>
			<td>Sigma</td>
			<td>P4170</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Bovine Serum Albumin (BSA)</td>
			<td>Sigma</td>
			<td>A7638-5G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triton-X100</td>
			<td>Promega</td>
			<td>H5142</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Poly-lysine&#160;</td>
			<td>Sigma</td>
			<td>P-4832</td>
			<td>Filter sterilize and store at 4 &#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vector&#160; pWPXLd</td>
			<td>Addgene</td>
			<td>12258</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vector pMD2.G</td>
			<td>Addgene</td>
			<td>12259</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vector psPAX2</td>
			<td>Addgene</td>
			<td>12260</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DNase I (RNase-free)</td>
			<td>New England Biolabs</td>
			<td>M0303S</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Oligo(dT)18 Primer</td>
			<td>Thermo Scientific</td>
			<td>SO131&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Anti-mouse secondary antibody (Anti-mouse IgG, HRP-linked Antibody)</td>
			<td>Cell Signaling Technology</td>
			<td>7076S</td>
			<td></td>
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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 ...

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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 ...

The overall goal of this protocol is to engineer artificial splicing factors that can specifically manipulate alternative splicing of a given target. This method can help to answer key questions in the field of RNA processing, such as the regulation and the misregulation of alternate splicing in cancer cells. The main advantage of this technique is its flexibility.We can design artificial factors that either promote or inhibit different type of alternate splicing in any given genes. Demonstrating this procedure will be Huan-Huan, a research associate of my laboratory, and Qianyun, a postdoc in my laboratory. Wild-type PUF DNA is used as a template for generating the customized PUF domain scaffold.Use PCR primers containing PUF sequences that specifically recognize different RNA nucleotides in each position. For each PUF repeat, use four different primers to recognize a different base on each position. In round one PCR, use the primer pairs shown to generate coding sequences for four PUF repeats, universal bridge fragments, and cap fragments.In round two, use the PCR products generated in the last step as templates with the primer combinations shown to generate coding sequences for RNA recognition codes R-one to R-four, and R-five to R-eight. In round three, use the products from round two and bridge four to five as templates with the R-one forward primer and R-eight reverse primer to generate coding sequences for R-one to R-eight without caps. In round four PCR, use R-one to R-eight, five-prime end cap and three-prime end cap as templates, to generate coding sequences for complete PUF domains.To begin transfection of HEK-293T cells, mix the liposomal transfection reagent by gently inverting the bottles. Then dilute two microliters of liposomal transfection reagent in 50 microliters of reduced serum medium per transfection. Mix gently, and then incubate for five minutes at room temperature.Next, dilute 04 micrograms of glycine-rich domain expression vector, and 0.2 micrograms of the modular splicing reporter plasmid in 50 microliters of reduced serum medium in a sterile tube. Then dilute 0.4 micrograms of RS-effector domain expression vector, and 0.2 micrograms of PGZ-three reporter plasmid in 50 microliters of reduced serum medium. Lastly, dilute 0.4 micrograms of PGL-RS-PUF expression vector and 0.2 micrograms of PEZ-1B or PEZ-2F reporter plasmids in 50 microliters of reduced serum medium in a sterile tube.After five minutes of incubation at room temperature, gently mix the diluted liposomal transfection reagent with the diluted plasmid mixtures. Incubate the final mixtures for 20 minutes at room temperature. Then add the transfection mixtures containing the expression vectors to each well of a 24-well plate seeded with HEK-293 cells, and incubate for at least 12 hours in a humidified incubator at 37 degrees Celsius and 5%carbon dioxide.After 12 hours of incubation, harvest the transfected cells by trypsinization and centrifugation. Following centrifugation, discard the medium and add 0.5 milliliters of RNA extraction buffer per tube. Add 0.1 milliliters of chloroform per 0.5 milliliters of RNA extraction buffer to each sample.Following the incubation, centrifuge the tubes for 15 minutes at 12, 000 times G and four degrees Celsius. Then transfer the aqueous base to a fresh tube. Add 0.25 milliliters of isopropanol per 0.5 milliliters of RNA extraction buffer used in the initial homogenization.Mix by vortexing, and incubate at room temperature for 10 minutes. After a centrifugation as before, the RNA precipitate is usually visible on the bottom of the tube. Discard the supernatant, and wash the RNA pellet with 0.5 milliliters of 75%ethanol per 0.5 milliliters of RNA extraction buffer.Vortex vigorously, and then centrifuge at 7, 500 times G for five minutes at four degrees Celsius. After the spin, remove the supernatant, and air-dry the RNA pellets. Dissolve the RNAs in 50 microliters of RNase-free water.Next, add two microliters of five units per microliter DNase-one, seven microliters of 10X buffer, and 11 microliters of water to each 50-microliter RNA solution. After the incubation, heat the solutions to 70 degrees Celsius for 15 minutes to inactivate the DNase. After performing a reverse transcriptase reaction to synthesize cDNA from each sample, add the components of the body labeled PCR reaction in the order shown on screen to PCR tubes.Prepare one reaction per sample. Run the RT-PCR program on the thermal cycler. Finally, resolve the PCR products by electrophoresis through a 10%polyacrylamide gel with TBE buffer.Use a fluorescence scanner to visualize the products, and measure the amount of each spliced isoform using densitometry software. For the immunofluorescence assay to measure apoptosis, prepare a transfection mix containing glycine-rich domain expression plasmids as previously shown, and transfect HeLa cells grown on polylysine-coated glass cover slips in a six-well plate. 24 hours after transfection, fix the cells on the cover slips with one milliliter of 4%paraformaldehyde in 1x PBS for 20 minutes at room temperature.Then gently wash the cells on the cover slips with two milliliters of 1x PBS for five minutes. Next, permeabilize the cells with 0.2%Triton X-100 in 1x PBS for 10 minutes. After washing three times with 1x PBS as before, block non-specific binding with 3%bovine serum albumin in 1x PBS for 10 minutes.Dilute the flag antibody one to 1, 000 in 3%BSA in PBS, and pipette 30 microliters of the diluted flag antibody onto parafilm sheet. Use forceps to remove a cover slip. Carefully dry off excess buffer with lab wipes, and then place the cover slip cell-side down on the anti-flag solution.Incubate for one hour at room temperature. Following the incubation, add approximately 500 microliters of 1x PBS to the cell-side of the cover slip until it floats on top of the solution. Return it to the six-well plate with 1x PBS in the wells.Incubate with secondary antibody on parafilm as before for 15 minutes. Wash as before, and then mount the cover slips on microscope slides using mounting medium containing DAPI. Visualize the cells using a fluorescence microscope, and photograph them using a digital camera.Using immunofluorescence microscopy, many cells expressing Gly-PUF-531 had fragmented nuclear DNA, indicating that they were undergoing apoptosis. As a control, cells expressing Gly-PUF wild-type had less fragmented nuclear DNA when compared to Gly-PUF-531 transfected cells. Here, immunofluorescence microscopy using the anti-flag antibody merged with DAPI-stained cells shows that the Gly-PUF-531 localized predominantly in the nuclei of transfected cells.Gly-PUF wild-type also localized in the nuclei of transfected cells, suggesting that these ESFs dissociate from their targets when the fully-spliced mRNAs are transported into the cytoplasm. The percentage of apoptotic cells with fragmented nuclear DNA was measures from randomly chosen fields of fluorescence microscopy images. Once mastered, the construction of PUF scaffolds with RNA binding specificity can be done in two days if it is performed properly.After watching this video, you should have a good understanding of how to specifically manipulate alternative splicing in human cells by engineering artificial factors.

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8.9K visualizações.  Shanghai Institutes for Biological Sciences (SIBS). The overall goal of this protocol is to engineer artificial splicing factors that can specifically manipulate alternative splicing of a given target. This method can help to answer key questions in the field of RNA processing, such as the regulation and the misregulation of alternate splicing in cancer cells. The main advantage of this technique is its flexibility.We can design artificial factors that either promote or inhibit different type of alternate splicing in any given genes. De...