We would like to thank all members of the Kerscher lab for their support, Nathalie Nguyen for critical reading of the manuscript, and Lidia Epp for sequencing. This work has been supported by the Commonwealth Research Commercialization fund MF16-034-LS to OK. Research support for W&#38;M students was provided by the Bailey-Huston Research fund, and Charles Center Honors Fellowships to RY and CH.

1. SUMO detection in fixed tissue culture cells using recombinant KmUTAG-FL SUMO-trapping protein
<ol>
	<li>Grow tissue culture cells of choice on 22 mm round cover slips in 6-well TC plates until 70%&#8211;80% confluent. Perform steps 1.2&#8211;1.8 in the 6-well plate.</li>
	<li>Wash cells briefly with 1 mL of DPBS (Dulbecco&#39;s phosphate-buffered saline)</li>
	<li>For fixation, prepare a fresh solution of 4% Paraformaldehyde (PFA) solution (diluted in DPBS). To fix cells, add 2 mL 4% PFA in DPBS to each well. Incubate the cells for 20 min at room temperature. NOTE: All steps using PFA should be performed in a laboratory safety hood and PFA must be disposed properly.</li>
	<li>Wash the fixed cells 3x in 1 mL DPBS while nutating the plate, 5 min each wash.</li>
	<li>To permeabilize cells, incubate for 15 min with 0.1% Triton X-100 in DPBS</li>
	<li>Wash the cells 3x in 1 mL DPBS while nutating the plate, 5 min each wash</li>
	<li>Incubate the cells with 500 &#181;L of 0.1 M Glycine-HCL (pH 2.0) for 10 s, then neutralize pH immediately with 500 &#181;L of 10x SUMO Protease Buffer (SPB).</li>
	<li>Wash the cells 3x in 1 mL DPBS while nutating plate, 5 min each wash</li>
	<li>Remove the coverslips from the well and place them in a humidity chamber. Then proceed with incubations on the coverslip as follows:
	<ol>
		<li>For UTAG-fl staining only: mix 1 &#181;g UTAG-fl with 100 &#181;L of 1x SPB containing 5 mM TCEP in a tube, pipette the mix onto the cells on the coverslip, and incubate at room temperature for 1 h in the humidity chamber.</li>
		<li>Optionally, for UTAG-FL and anti SUMO1 antibody co-staining, proceed with the following:
		<ol>
			<li>Mix in a tube 1 &#181;g UTAG-FL and 0.5 &#181;L SUMO2/3 8A2 (obtained for Developmental Studies Hybridoma Bank9) with 100 &#181;L of blocking buffer, pipette the mix onto the coverslip, and incubate in room temperature for 1 h.</li>
			<li>Wash cells on the coverslip 3 times with 200 &#181;L DPBS, 5 min each wash.</li>
			<li>Mix in a tube 0.5 &#181;L anti-mouse Alexa Fluor 488 conjugated antibody with 100 &#181;L Blocking buffer, pipette the mix onto the coverslip, and incubate in room temperature for 1 h.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>To wash coverslips, pipette 200 &#181;L DPBS on each coverslip and leave in place for 10 min. Repeat the wash 2 more times.</li>
	<li>Remove coverslip from the last wash and invert it onto a pre-cleaned microscopy slide with a drop of mounting medium (see Table of Materials).</li>
	<li>Store overnight in a -20&#176;C freezer before viewing under the microscope. Visualize using the appropriate filter sets for DAPI (DNA), Texas Red (kmUTAG-fl), and Alexa Fluor 488 (if optional SUMO2/3 co-staining is performed).</li>
</ol>
2. SUMO detection in fixed nematode gonads using UTAG-fl
<ol>
	<li>Transfer adult hermaphrodites to an 8 &#181;L droplet of egg buffer14 on a plus-charged slide that has been coated with poly-L-lysine. Release gonads from the worms using 27.5 G needles. Proceed with either antibody labeling or UTAG-fl labeling.</li>
	<li>For antibody labeling samples, proceed as follows:
	<ol>
		<li>Freeze-crack samples in liquid nitrogen and then fix overnight in -20 &#176;C methanol in a Coplin jar.</li>
		<li>Also in Coplin jars, wash slides for 3 times in 1x PBS, then block for 20 min in PBS containing 0.5% BSA and 0.1% Tween 20.</li>
		<li>Add 30 &#181;L of anti-SUMO 6F2 antibody (1:10) to each slide covering the specimens. Incubate overnight in a humidity chamber at 4 &#176;C. 
		NOTE: SUMO 6F2 was obtained from the Developmental Studies Hybridoma Bank15.</li>
		<li>In Coplin jars, wash slides for 2 min in 1x PBS, then cover and incubate specimens with 30 &#181;L of DyLight 488 goat-anti mouse secondary antibody (1:200) for 1.5 hours in a humidity chamber at room temperature.</li>
		<li>In Coplin jars, wash slides for 2 min in 1x PBS, perform a quick dip in dH20, and then mount the slides with mounting medium (see Table of Materials).</li>
	</ol>
	</li>
	<li>For KmUTAG-fl labeling, proceed with the following:
	<ol>
		<li>To fix cells, add 1 volume of 8% PF to samples for a final concentration of 4% PF. Fix for 10 min in a humidity chamber and then quench the reaction by transferring slides to a Coplin jar containing 1x PBS with 0.1 M glycine for at least 5 min.</li>
		<li>In Coplin jars, wash cells for 5 min in 1x PBS, then permeabilize the samples in 1x PBS containing 0.1% Triton-X for 10 min.</li>
		<li>Wash in a Coplin jar for at least 5 min in 1x PBS, then add 200 &#181;L of 0.1 M Glycine-HCl (pH = 2.0) to the samples on the slide for 10 seconds. Immediately add 200 &#181;L of 10x SPB to neutralize the pH.</li>
		<li>Wash the slide in 1x PBS in a Coplin jar for 5 min.</li>
		<li>Remove slide from wash and pipette 100 &#181;L of 1x SPB + 5mM TCEP containing 2 &#181;g of UTAG-fl to the nematodes on the slides, and incubate in humidity chamber for 1 h without rocking.</li>
		<li>Return the slide to the Coplin jar and wash for 15 min in 1x PBS</li>
		<li>Remove the slide from the wash, use a laboratory wipe to dry around the sample, and then mount the slides with 5 &#181;L of mounting medium (see Table of Materials). Store the slides at 4 &#176;C. Visualize using the appropriate filter sets for DAPI (DNA), Texas Red (kmUTAG-fl), and DyLight 488 (SUMO2/3).</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Kerscher, O., Felberbaum, R., Hochstrasser, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Modification+of+proteins+by+ubiquitin+and+ubiquitin-like+proteins.">Modification of proteins by ubiquitin and ubiquitin-like proteins.</a> Cell and Developmental Biology. 22, 159-180 (2006).</li><li>Kerscher, 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> SUMOylation. , 1-11 (2016).</li><li>Hay, R. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SUMO:+a+history+of+modification.">SUMO: a history of modification.</a> Molecular Cell. 18 (1), 1-12 (2005).</li><li>Fu, J., 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=Disruption+of+SUMO-specific+protease+2+induces+mitochondria+mediated+neurodegeneration.">Disruption of SUMO-specific protease 2 induces mitochondria mediated neurodegeneration.</a> PLoS Genetics. 10 (10), e1004579-e1004579 (2014).</li><li>Zhang, H., Kuai, X., Ji, Z., Li, Z., Shi, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Over-expression+of+small+ubiquitin-related+modifier-1+and+sumoylated+p53+in+colon+cancer.">Over-expression of small ubiquitin-related modifier-1 and sumoylated p53 in colon cancer.</a> Cell biochemistry and biophysics. 67 (3), 1081-1087 (2013).</li><li>Wang, Q., 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=SUMO-specific+protease+1+promotes+prostate+cancer+progression+and+metastasis.">SUMO-specific protease 1 promotes prostate cancer progression and metastasis.</a> Oncogene. 32 (19), 2493-2498 (2013).</li><li>Karami, 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=Novel+SUMO-Protease+SENP7S+Regulates+&#946;-catenin+Signaling+and+Mammary+Epithelial+Cell+Transformation.">Novel SUMO-Protease SENP7S Regulates &#946;-catenin Signaling and Mammary Epithelial Cell Transformation.</a> Scientific Reports. 7 (1), 46477 (2017).</li><li>Pelisch, F., 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+SUMO-Dependent+Protein+Network+Regulates+Chromosome+Congression+during+Oocyte+Meiosis.">A SUMO-Dependent Protein Network Regulates Chromosome Congression during Oocyte Meiosis.</a> Molecular Cell. 65 (1), 66-77 (2017).</li><li>Zhang, X. D., 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=SUMO-2/3+modification+and+binding+regulate+the+association+of+CENP-E+with+kinetochores+and+progression+through+mitosis.">SUMO-2/3 modification and binding regulate the association of CENP-E with kinetochores and progression through mitosis.</a> Molecular Cell. 29 (6), 729-741 (2008).</li><li>Baker, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reproducibility+crisis:+Blame+it+on+the+antibodies.">Reproducibility crisis: Blame it on the antibodies.</a> Nature News. 521 (7552), 274-276 (2015).</li><li>Wang, Z., Prelich, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quality+control+of+a+transcriptional+regulator+by+SUMO-targeted+degradation.">Quality control of a transcriptional regulator by SUMO-targeted degradation.</a> Molecular and Cellular Biology. 29 (7), 1694-1706 (2009).</li><li>Li, S. J., Hochstrasser, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+protease+required+for+cell-cycle+progression+in+yeast.">A new protease required for cell-cycle progression in yeast.</a> Nature. 398 (6724), 246-251 (1999).</li><li>Peek, J., 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=SUMO+targeting+of+a+stress-tolerant+Ulp1+SUMO+protease.">SUMO targeting of a stress-tolerant Ulp1 SUMO protease.</a> PLoS ONE. 13 (1), e0191391 (2018).</li><li>Edgar, L. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+13+Blastomere+Culture+and+Analysis.">Chapter 13 Blastomere Culture and Analysis.</a> Methods in Cell Biology. 48, 303-321 (1995).</li><li>Pelisch, F., 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=Dynamic+SUMO+modification+regulates+mitotic+chromosome+assembly+and+cell+cycle+progression+in+Caenorhabditis+elegans.">Dynamic SUMO modification regulates mitotic chromosome assembly and cell cycle progression in Caenorhabditis elegans.</a> Nature Communications. 5 (1), 769 (2014).</li><li>Dillingham, M. 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=Fluorescent+single-stranded+DNA+binding+protein+as+a+probe+for+sensitive,+real-time+assays+of+helicase+activity.">Fluorescent single-stranded DNA binding protein as a probe for sensitive, real-time assays of helicase activity.</a> Biophysical Journal. 95 (7), 3330-3339 (2008).</li><li>Ruckman, J., 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=2'-Fluoropyrimidine+RNA-based+aptamers+to+the+165-amino+acid+form+of+vascular+endothelial+growth+factor+(VEGF165).+Inhibition+of+receptor+binding+and+VEGF-induced+vascular+permeability+through+interactions+requiring+the+exon+7-encoded+domain.">2'-Fluoropyrimidine RNA-based aptamers to the 165-amino acid form of vascular endothelial growth factor (VEGF165). Inhibition of receptor binding and VEGF-induced vascular permeability through interactions requiring the exon 7-encoded domain.</a> The Journal of Biological Chemistry. 273 (32), 20556-20567 (1998).</li><li>Hughes, D. J., 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=Generation+of+specific+inhibitors+of+SUMO-1-+and+SUMO-2/3-mediated+protein-protein+interactions+using+Affimer+(Adhiron)+technology.">Generation of specific inhibitors of SUMO-1- and SUMO-2/3-mediated protein-protein interactions using Affimer (Adhiron) technology.</a> Science Signaling. 10 (505), eaaj2005 (2017).</li><li>Lopata, A., 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=Affimer+proteins+for+F-actin:+novel+affinity+reagents+that+label+F-actin+in+live+and+fixed+cells.">Affimer proteins for F-actin: novel affinity reagents that label F-actin in live and fixed cells.</a> Scientific Reports. 8 (1), 6572 (2018).</li><li>Gilbreth, R. N., 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=Isoform-specific+monobody+inhibitors+of+small+ubiquitin-related+modifiers+engineered+using+structure-guided+library+design.">Isoform-specific monobody inhibitors of small ubiquitin-related modifiers engineered using structure-guided library design.</a> Proceedings of the National Academy of Sciences of the United States of America. 108 (19), 7751-7756 (2011).</li><li>Berndt, A., Wilkinson, K. A., Heimann, M. J., Bishop, P., Henley, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+characterization+of+the+properties+of+SUMO1-specific+monobodies.">In vivo characterization of the properties of SUMO1-specific monobodies.</a> Biochemical Journal. 456 (3), 385-395 (2013).</li></ol>

Recombinant kmUTAG reagents are provided to the research community via Kerafast.com.

Here we introduce the use of kmUTAG-fl, a recombinant protein, for functional studies of SUMO in fixed mammalian cells and dissected nematode gonads. KmUTAG-fl is a stress-tolerant pan-SUMO specific reagent that recognizes and traps native SUMO-conjugated proteins and SUMO chains. Since SUMO&#39;s tertiary structure is highly conserved it is very likely that SUMO variants from additional model and non-model systems can be analyzed with the kmUTAG-fl reagent. As such, KmUTAG-fl may represent a useful alternative or second...

The purpose of this method is to facilitate the study and analysis of SUMO-conjugated proteins using the recombinant SUMO-trapping UTAG (Ulp domain Tag) protein. As detailed below, UTAG can be used in lieu of other reagents and approaches to purify, detect, and visualize SUMO-modified proteins. Depending on growth conditions, cells may contain hundreds or thousands of proteins that are modified with SUMO or SUMO chains (for review see Kerscher et al. 20061 and Kerscher 20162). This represents a considerable difficulty for the functional analyses of specific SUMO-modified proteins, especially since only a fraction of a particular sumoylation target is actually modified3. In addition to their roles in essential cellular processes such as transcriptional regulation, protein homeostasis, the response to cellular stress, and chromatin remodeling during mitosis and meiosis; it has now become sufficiently clear that SUMO, SUMO-modified proteins, and SUMO pathway components also have potential as biomarkers for pathologies such as cancer and neurodegenerative disorders4,5,6,7. This underscores the need for robust, reliable, and readily available tools and innovative approaches for the detection and functional analysis of SUMO-modified proteins in a variety of cells and samples.
In many systems, SUMO-specific antibodies are the reagents of choice for the detection, isolation and functional analyses of SUMO-modified proteins8,9. However, some commercially available SUMO-specific antibodies are expensive, limited in quantity or availability, prone to exhibit wildly variable affinities and cross-reactivity, and in some instances lack reproducibility10. One alternative approach is the expression of epitope-tagged SUMO in transformed cells and organisms, but linking epitope tags to SUMO may artificially lower its conjugation to protein targets11. Additionally, epitopes are not useful when untransformed cells or tissues are evaluated.
Ulp1 is a conserved SUMO protease from S. cerevisiae that both processes the SUMO precursor and desumoylates SUMO-conjugated proteins12. We developed the UTAG reagent based on the serendipitous observation that a mutation of the catalytic Cysteine (C580S) in Ulp1&#39;s SUMO processing Ulp domain (UD) not only prevents SUMO cleavage but also traps SUMO-conjugated proteins with high avidity12. For simplicity, we referred to this carboxy-terminal SUMO-trapping Ulp1(C580S) fragment as UTAG (short for UD TAG). UTAG is a recombinant pan-SUMO trapping protein that represents a useful alternative to anti-SUMO antibodies used for the isolation and detection of SUMO-modified proteins. Importantly, it specifically recognizes natively-folded, conjugated SUMO and not just one or several epitopes on SUMO. To improve both the protein stability and SUMO binding strength of UTAG, we generated a variant of UTAG from the stress-tolerant yeast Kluyveromyces marxianus (Km). KmUTAG tightly binds SUMO-conjugates with nanomolar affinity13. Additionally, kmUTAG is resistant to elevated temperatures (42 &#176;C), reducing agents (5 mM TCEP - Tris(2-carboxyethyl)phosphine hydrochloride), denaturants (up to 2 M Urea), oxidizing agents (0.6% hydrogen peroxide), and non-ionic detergents. This stress tolerance is beneficial during harsh purification condition and prolonged incubation times, ensuring its stability and SUMO-trapping activity. Not surprisingly, however, KmUTAG&#39;s SUMO-trapping activity is incompatible with cysteine-modifying reagents, ionic detergents and fully denatured protein extracts. The remarkable affinity and properties of KmUTAG indicate that this reagent may become part of the standard repertoire for the study of sumoylated proteins in multiple species.
Here we provide a simple method to detect SUMO-modified proteins in mammalian cells and nematodes using a recombinant fluorescent mCherry-KmUTAG fusion protein (kmUTAG-fl).

<table>
	<tbody>
		<tr>
			<td>16% Paraformaldehyde (formaldehyde) aqueous solution</td>
			<td>Electron Microscopy Sciences</td>
			<td>30525-89-4</td>
			<td></td>
		</tr>
		<tr>
			<td>6-Well Cell Culture Plates</td>
			<td>Genesee Scientific/Olympus Plastics</td>
			<td>25-105</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa Fluor 488 AffiniPure Goat Anti-Mouse IgG (H+L)</td>
			<td>Jackson ImmunoResearch</td>
			<td>115-545-003</td>
			<td>Used as a secondary antibody for mouse monoclonal antibody</td>
		</tr>
		<tr>
			<td>DPBS, no calcium, no magnesium</td>
			<td>Fisher Scientific</td>
			<td>Gibco 14190144</td>
			<td></td>
		</tr>
		<tr>
			<td>Dylight 488 conjugated AffiniPure Goat Anti-Moue IgG (H+L)</td>
			<td>Jackson ImmunoResearch</td>
			<td>115-485-146</td>
			<td>Used as a secondary antibody for mouse monoclonal antibody</td>
		</tr>
		<tr>
			<td>Fisherbrand Coverglass for Growth Cover Glasses</td>
			<td>Fisherbrand</td>
			<td>12545101</td>
			<td></td>
		</tr>
		<tr>
			<td>FLUORO-GEL II with DAPI</td>
			<td>Electron Microscopy Sciences</td>
			<td>50-246-93)</td>
			<td>Mounting media in step 1.11</td>
		</tr>
		<tr>
			<td>FLUORO-GEL with DABCO</td>
			<td>Electron Microscopy Sciences</td>
			<td>17985-02</td>
			<td>With DAPI added to 1 &#181;g/mL; mounting media in step 2.2.5</td>
		</tr>
		<tr>
			<td>Glycine-HCl</td>
			<td>Fisher BioReagents</td>
			<td>BP3815</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine-HCl</td>
			<td>ACROS Organics</td>
			<td>6000-43-7</td>
			<td></td>
		</tr>
		<tr>
			<td>KmUTAG-fl</td>
			<td>Kerafast</td>
			<td></td>
			<td>KmUTAG reagents are available on Kerafast.com</td>
		</tr>
		<tr>
			<td>Oneblock Western-CL blocking buffer</td>
			<td>Prometheus</td>
			<td>20-313</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS, Phosphate Buffered Saline, 10X Solution</td>
			<td>Fisher BioReagents</td>
			<td>BP3994</td>
			<td></td>
		</tr>
		<tr>
			<td>PNT2 cell line</td>
			<td>Sigma-Aldrich</td>
			<td>95012613</td>
			<td>Normal prostate epithelium immortalized with SV40.</td>
		</tr>
		<tr>
			<td>pSPOT1</td>
			<td>(ChromoTek GmbH)</td>
			<td>ev-1</td>
			<td>https://www.chromotek.com/fileadmin/user_upload/pdfs/Datasheets/pSpot1_v1.pdf</td>
		</tr>
		<tr>
			<td>SUMO 6F2</td>
			<td>DSHB</td>
			<td>SUMO 6F2</td>
			<td>SUMO 6F2 was deposited to the DSHB by Pelisch, F. / Hay, R.T. (DSHB Hybridoma Product SUMO 6F2)</td>
		</tr>
		<tr>
			<td>SUMO protease buffer [10x]</td>
			<td></td>
			<td></td>
			<td>500 mM Tris-HCl, pH 8.0, 2% NP-40, 1.5 M NaCl</td>
		</tr>
		<tr>
			<td>SUMO-2 Antibody 8A2</td>
			<td>DSHB</td>
			<td>SUMO-2 8A2</td>
			<td>SUMO-2 8A2 was deposited to the DSHB by Matunis, M. (DSHB Hybridoma Product SUMO-2 8A2)</td>
		</tr>
		<tr>
			<td>TCEP-HCL</td>
			<td>GoldBio</td>
			<td>51805-45-9</td>
			<td>Used as a reducing agent at a concentration of 5mM</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Fisher BioReagents</td>
			<td>9002-93-1</td>
			<td>Used for permeablization at 0.1% in DPBS/PBS(for worms)</td>
		</tr>
	</tbody>
</table>

localization of sumo-modified proteins using fluorescent sumo-trapping proteins

Here we are presenting a novel method to study the sumoylation of proteins and their sub-cellular localization in mammalian cells and nematode oocytes. This method utilizes a recombinant modified SUMO-trapping protein fragment, kmUTAG, derived from the Ulp1 SUMO protease of the stress-tolerant budding yeast Kluyveromyces marxianus. We have adapted the properties of the kmUTAG for the purpose of studying sumoylation in a variety of model systems without the use of antibodies. For the study of SUMO, KmUTAG has several advantages when compared to antibody-based approaches. This stress-tolerant SUMO-trapping reagent is produced recombinantly, it recognizes native SUMO isoforms from many species, and unlike commercially available antibodies it shows reduced affinity for free, unconjugated SUMO. Representative results shown here include the localization of SUMO conjugates in mammalian tissue culture cells and nematode oocytes.

KmUTAG-fl is a recombinant, mCherry-tagged SUMO-trapping protein. To produce kmUTAG-fl, we cloned a codon-optimized mCherry-kmUTAG into the pSPOT1 bacterial overexpression plasmid (Figure 1). After induction, the kmUTAG-fl protein was purified on Spot-TRAP, eluted, and frozen until further use. To ensure the SUMO-trapping activity of KmUTAG-fl, we confirmed binding to SUMO1-conjugated beads and precipitation of a SUMO-CAT fusion protein (data not shown, but s...

Watch this Scientific Journal Video about Localization of SUMO-modified Proteins Using Fluorescent Sumo-trapping Proteins at JoVE.com

Localization of SUMO-modified Proteins Using Fluorescent Sumo-trapping Proteins

SUMO is an essential and highly conserved, small ubiquitin-like modifier protein. In this protocol we are describing the use of a stress-tolerant recombinant SUMO-trapping protein (kmUTAG) to visualize native, untagged SUMO conjugates and their localization in a variety of cell types.

Here we are presenting a novel method to study the sumoylation of proteins and their sub-cellular localization in mammalian cells and nematode oocytes. ...

localization-sumo-modified-proteins-using-fluorescent-sumo-trapping

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JoVE Journal

Biochemistry

8.4K Views.  College of William & Mary. SUMO is an essential and highly conserved, small ubiquitin-like modifier protein. In this protocol we are describing the use of a stress-tolerant recombinant SUMO-trapping protein (kmUTAG) to visualize native, untagged SUMO conjugates and their localization in a variety of cell types.

Video: Localization of SUMO-modified Proteins Using Fluorescent Sumo-trapping Proteins

Detection of Detergent-sensitive Interactions Between Membrane Proteins

Our ability to explore protein-protein interactions is the key to understanding regulatory connections in the cell. However, detection of protein-protein interactions in many cases is associated with significant experimental challenges. In particular, sorting receptors interact with their protein cargo in the lumen of the membrane compartments often in a detergent-sensitive fashion, making co-immunoprecipitation of these proteins unusable. Binding of the sorting receptor sortilin to glucose transporter GLUT4 may serve as an example of weak luminal interactions between membrane proteins. Here, we describe a fast, simple, and inexpensive assay to validate the interaction between sortilin and GLUT4. For that, we have designed and chemically synthesized the myc-tagged peptide corresponding to the potential sortilin-binding epitope in the luminal part of GLUT4. Sortilin tagged with six histidines was expressed in mammalian cells, and isolated from cell lysates using Cobalt beads. Sortilin immobilized on the beads was incubated with the peptide solution at different pH values, and the eluted material was analyzed by Western blotting. This assay can be easily adapted to study other detergent-sensitive protein-protein interactions.

We describe a protocol for detection of detergent-sensitive interactions between membrane proteins using binding of the sorting receptor, sortilin, to the first luminal loop of the glucose transporter protein, GLUT4, as an example.

Our ability to explore protein-protein interactions is the key to understanding regulatory connections in the cell. However, detection of protein-protein ...

How to Quantify the Fraction of Photoactivated Fluorescent Proteins in Bulk and in Live Cells

Photoactivatable and -convertible fluorescent proteins (PA-FPs) have been used in fluorescence live-cell microscopy for analyzing the dynamics of cells and protein ensembles. Thus far, no method has been available to quantify in bulk and in live cells how many of the PA-FPs expressed are photoactivated to fluoresce.
Here, we present a protocol involving internal rulers, i.e., genetically coupled spectrally distinct (photoactivatable) fluorescent proteins, to ratiometrically quantify the fraction of all PA-FPs expressed in a cell that are switched on to be fluorescent. Using this protocol, we show that different modes of photoactivation yielded different photoactivation efficiencies. Short high-power photoactivation with a confocal laser scanning microscope (CLSM) resulted in up to four times lower photoactivation efficiency than hundreds of low-level exposures applied by CLSM or a short pulse applied by widefield illumination. While the protocol has been exemplified here for (PA-)GFP and (PA-)Cherry, it can in principle be applied to any spectrally distinct photoactivatable or photoconvertible fluorescent protein pair and any experimental set-up.

Here, we present a protocol that involves genetically coupled spectrally distinct photoactivatable and fluorescent proteins. These fluorescent protein chimeras permit quantification of the PA-FP fraction that is photoactivated to be fluorescent, i.e., the photoactivation efficiency. The protocol reveals that different modes of photoactivation yield different photoactivation efficiencies.

Photoactivatable and -convertible fluorescent proteins (PA-FPs) have been used in fluorescence live-cell microscopy for analyzing the dynamics of cells ...

Fluorescent Silver Staining of Proteins in Polyacrylamide Gels

Silver staining is a colorimetric technique widely used to visualize protein bands in polyacrylamide gels following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The classic silver stains have certain drawbacks, such as high background staining, poor protein recovery, low reproducibility, a narrow linear dynamic range for quantification, and limited compatibility with mass spectrometry (MS). Now, with the use of a fluorogenic Ag+ probe, TPE-4TA, we developed a fluorescent silver staining method for the total protein visualization in polyacrylamide gels. This new stain avoids the troublesome silver reduction step in traditional silver stains. Moreover, the fluorescent silver stain demonstrates good reproducibility, sensitivity, and linear quantification in protein detection, making it a useful and practical protein gel stain.

Here, we describe a detailed protocol outlining a new fluorescent staining technique for total protein detection in polyacrylamide gels. The protocol utilizes a silver ion-specific fluorescence turn-on probe, which detects Ag+-protein complexes, and eliminates certain limitations of traditional chromogenic silver stains.

Silver staining is a colorimetric technique widely used to visualize protein bands in polyacrylamide gels following sodium dodecyl sulfate-polyacrylamide ...

Use of Recombinant Fusion Proteins in a Fluorescent Protease Assay Platform and Their In-gel Renaturation

Proteases are intensively studied enzymes due to their essential roles in several biological pathways of living organisms and in pathogenesis; therefore, they are important drug targets. We have developed a magnetic-agarose-bead-based assay platform for the investigation of proteolytic activity, which is based on the use of recombinant fusion protein substrates. In order to demonstrate the use of this assay system, a protocol is presented on the example of human immunodeficiency virus type 1 (HIV-1) protease. The introduced assay platform can be utilized efficiently in the biochemical characterization of proteases, including enzyme activity measurements in mutagenesis, kinetic, inhibition, or specificity studies, and it may be suitable for high-throughput substrate screening or may be adapted to other proteolytic enzymes.
In this assay system, the applied substrates contain N-terminal hexahistidine (His6) and maltose-binding protein (MBP) tags, cleavage sites for tobacco etch virus (TEV) and HIV-1 proteases, and a C-terminal fluorescent protein. The substrates can be efficiently produced in Escherichia coli cells and easily purified using nickel (Ni)-chelate-coated beads. During the assay, the proteolytic cleavage of bead-attached substrates leads to the release of fluorescent cleavage fragments, which can be measured by fluorimetry. Additionally, cleavage reactions can be analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A protocol for the in-gel renaturation of assay components is also described, as partial renaturation of fluorescent proteins enables their detection based on molecular weight and fluorescence.

Here, we present the detailed procedure of a recently developed protease assay platform utilizing N-terminal hexahistidine/maltose-binding protein and fluorescent protein-fused recombinant substrates attached to the surface of nickel-nitrilotriacetic acid magnetic agarose beads. A subsequent in-gel analysis of the assay samples separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis is also presented.

Proteases are intensively studied enzymes due to their essential roles in several biological pathways of living organisms and in pathogenesis; therefore, ...

Characterizing Cellular Proteins with In-cell Fast Photochemical Oxidation of Proteins

Fast photochemical oxidation of proteins (FPOP) is a hydroxyl radical protein footprinting method used to characterize protein structure and interactions. FPOP uses a 248 nm excimer laser to photolyze hydrogen peroxide producing hydroxyl radicals. These radicals oxidatively modify solvent exposed side chains of 19 of the 20 amino acids. Recently, this method has been used in live cells (IC-FPOP) to study protein interactions in their native environment. The study of proteins in cells accounts for intermolecular crowding and various protein interactions that are disrupted for in vitro studies. A custom single cell flow system was designed to reduce cell aggregation and clogging during IC-FPOP. This flow system focuses the cells past the excimer laser individually, thus ensuring consistent irradiation. By comparing the extent of oxidation produced from FPOP to the protein&#39;s solvent accessibility calculated from a crystal structure, IC-FPOP can accurately probe the solvent accessible side chains of proteins.

Here, we characterize protein structure and interaction sites in living cells using a protein footprinting technique termed in-cell fast photochemical oxidation of proteins (IC-FPOP).

Fast photochemical oxidation of proteins (FPOP) is a hydroxyl radical protein footprinting method used to characterize protein structure and interactions. ...

Transverse Sectioning of Mature Rice (Oryza sativa L.) Kernels for Scanning Electron Microscopy Imaging Using Pipette Tips as Immobilization Support

Starch granules (SGs) exhibit different morphologies depending on the plant species, especially in the endosperm of the Poaceae family. Endosperm phenotyping can be used to classify genotypes based on SG morphotype using scanning electron microscopic (SEM) analysis. SGs can be visualized using SEM by slicing through the kernel (pericarp, aleurone layers, and endosperm) and exposing the organellar contents. Current methods require the rice kernel to be embedded in plastic resin and sectioned using a microtome or embedded in a truncated pipette tip and sectioned by hand using a razor blade. The former method requires specialized equipment and is time-consuming, while the latter introduces a new host of problems depending on rice genotype. Chalky rice varieties, particularly, pose a problem for this type of sectioning due to the friable nature of their endosperm tissue. Presented here is a technique for preparing translucent and chalky rice kernel sections for microscopy, requiring only pipette tips and a scalpel blade. Preparing the sections within the confines of a pipette tip prevents rice kernel endosperm from shattering (for translucent or &#8216;vitreous&#8217; phenotypes) and crumbling (for chalky phenotypes). Using this technique, endosperm cell patterning and the structure of intact SGs can be observed.

Transverse Sectioning of Mature Rice Oryza sativa L. Kernels for Scanning Electron Microscopy Imaging Using Pipette Tips as Immobilization Support

This protocol allows for the preparation of transverse sections of cereal seeds (e.g., rice) for the analysis of endosperm and starch granule morphology using scanning electron microscopy.

Starch granules (SGs) exhibit different morphologies depending on the plant species, especially in the endosperm of the Poaceae family. Endosperm ...

Optimized Incorporation of Alkynyl Fatty Acid Analogs for the Detection of Fatty Acylated Proteins using Click Chemistry

Fatty acylation, the covalent addition of saturated fatty acids to protein substrates, is important in regulating a myriad of cellular functions in addition to its implications in cancer and neurodegenerative diseases. Recent developments in fatty acylation detection methods have enabled efficient and non-hazardous detection of fatty acylated proteins, particularly through the use of click chemistry with bio-orthogonal labeling. However, click chemistry detection can be limited by the poor solubility and potential toxic effects of adding long chain fatty acids to cell culture. Described here is a labeling approach with optimized delivery using saponified fatty acids in combination with fatty-acid free BSA, as well as delipidated media, which can improve detection of hard to detect fatty acylated proteins. This effect was most pronounced with the alkynyl-stearate analog, 17-ODYA, which has been the most commonly used fatty acid analog in click chemistry detection of acylated proteins. This modification will improve cellular incorporation and increase sensitivity to acylated protein detection. In addition, this approach can be applied in a variety of cell types and combined with other assays such as pulse-chase analysis, stable isotope labeling with amino acids in cell culture, and mass spectrometry for quantitative profiling of fatty acylated proteins.

The study of fatty acylation has important implications in cellular protein interactions and diseases. Presented here is a modified protocol to improve click chemistry detection of fatty acylated proteins, which can be applied in various cell types and combined with other assays, including pulse-chase and mass spectrometry.

Fatty acylation, the covalent addition of saturated fatty acids to protein substrates, is important in regulating a myriad of cellular functions in ...

Production of Recombinant PRMT Proteins using the Baculovirus Expression Vector System

Protein arginine methyltransferases (PRMTs) methylate arginine residues on a wide variety of proteins that play roles in numerous cellular processes. PRMTs can either mono- or dimethylate arginine guanidino groups symmetrically or asymmetrically. The enzymology of these proteins is a complex and intensely investigated area that requires milligram quantities of high-quality recombinant protein. The baculovirus expression vector system (BEVS) employing Autographa californica multiple nucleopolyhedrovirus (AcMNPV) and Spodoptera frugiperda 9 (Sf9) insect cells has been used for expression screening and production of many PRMTs, including PRMT 1, 2, and 4 through 9. To simultaneously screen for the expression of multiple constructs of these proteins, including domains and truncated fragments as well as the full-length proteins, we have applied scalable methods utilizing adjustable and programmable multichannel pipettes, combined with 24- and 96-well plates and blocks. Overall, these method adjustments enabled a large-scale generation of bacmid DNA, recombinant viruses, and protein expression screening. Using culture vessels with a high-fill volume of Sf9 cell suspension helped to overcome space limitations in the production pipeline for single batch large-scale protein production. Here, we describe detailed protocols for the efficient and cost-effective expression of functional PRMTs for biochemical, biophysical, and structural studies.

The baculovirus expression vector system (BEVS) is a robust platform for expression screening and production of protein arginine methyltransferases (PRMTs) to be used for biochemical, biophysical, and structural studies. Milligram quantities of material can be produced for the majority of PRMTs and other proteins of interest requiring a eukaryotic expression platform.

Protein arginine methyltransferases (PRMTs) methylate arginine residues on a wide variety of proteins that play roles in numerous cellular processes. ...

Analyzing the Interaction of Fluorescent-Labeled Proteins with Artificial Phospholipid Microvesicles using Quantitative Flow Cytometry

In the human body, most of the major physiologic reactions involved in the immune response and blood coagulation proceed on the membranes of cells. An important first step in any membrane-dependent reaction is binding of protein on the phospholipid membrane. An approach to studying protein interaction with lipid membranes has been developed using fluorescently labeled proteins and flow cytometry. This method allows the study of protein-membrane interactions using live cells and natural or artificial phospholipid vesicles. The advantage of this method is the simplicity and availability of reagents and equipment. In this method, proteins are labeled using fluorescent dyes. However, both self-made and commercially available, fluorescently labeled proteins can be used. After conjugation with a fluorescent dye, the proteins are incubated with a source of the phospholipid membrane (microvesicles or cells), and the samples are analyzed by flow cytometry. The obtained data can be used to calculate the kinetic constants and equilibrium Kd. In addition, it is possible to estimate the approximate number of protein binding sites on the phospholipid membrane using special calibration beads.

Here, we describe a set of methods for characterizing the interaction of proteins with membranes of cells or microvesicles.

In the human body, most of the major physiologic reactions involved in the immune response and blood coagulation proceed on the membranes of cells. An ...

Purification of Ubiquitinated p53 Proteins from Mammalian Cells

Ubiquitination is a type of posttranslational modification that regulates not only the stability but also the localization and function of a substrate protein. The ubiquitination process occurs intracellularly in eukaryotes and regulates almost all basic cellular biological processes. Purification of ubiquitinated proteins aids the investigation of the role of ubiquitination in controlling the function of substrate proteins. Here, a step-by-step procedure to purify ubiquitinated proteins in mammalian cells is described with the p53 tumor suppressor protein as an example. Ubiquitinated p53 proteins were purified under stringent nondenaturing and denaturing conditions. Total cellular Flag-tagged p53 protein was purified with anti-Flag antibody-conjugated agarose under nondenaturing conditions. Alternatively, total cellular His-tagged ubiquitinated protein was purified using nickel-charged resin under denaturing conditions. Ubiquitinated p53 proteins in the eluates were successfully detected with specific antibodies. Using this procedure, the ubiquitinated forms of a given protein can be efficiently purified from mammalian cells, facilitating studies on the roles of ubiquitination in regulating protein function.

The protocol describes a step-by-step method to purify ubiquitinated proteins from mammalian cells using the p53 tumor suppressor protein as an example. Ubiquitinated p53 proteins were purified from cells under stringent nondenaturing and denaturing conditions.

Ubiquitination is a type of posttranslational modification that regulates not only the stability but also the localization and function of a substrate ...