Name: chemical dimerization-induced protein condensates on telomeres
Uploaded: 2021-04-12T13:00:00
Description: Watch this Scientific Journal Video about Chemical Dimerization-Induced Protein Condensates on Telomeres at JoVE.com

This work was supported by US National Institutes of Health (1K22CA23763201 to H.Z., GM118510 to D.M.C.) and Charles E. Kaufman foundation to H.Z. The authors would like to thank Jason Tones for proofreading the manuscript.

1. Production of transient cell lines
<ol>
	<li>Culture U2OS acceptor cells on 22 x 22 mm glass coverslips (for live imaging) or 12 mm diameter circular coverslips (for IF or FISH) coated with poly-D-lysine in 6-well plate with growth medium (10% fetal bovine serum and 1% Penicillin-Streptomycin solution in DMEM) until they reach 60-70% confluency.</li>
	<li>Replace growth medium with 1 mL transfection medium (growth medium without Penicillin-Streptomycin solution) prior to transfection.</li>
	<li>For ...

<ol>
	<li>Shin, Y., Brangwynne, C. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liquid+phase+condensation+in+cell+physiology+and+disease.">Liquid phase condensation in cell physiology and disease.</a> Science. 357 (6357), (2017).</li><li>Banani, S. F., Lee, H. O., Hyman, A. A., Rosen, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomolecular+condensates:+organizers+of+cellular+biochemistry.">Biomolecular condensates: organizers of cellular biochemistry.</a> Nature Reviews Molecular Cell Biology. 18 (5), 285-298 (2017).</li><li>Sabari, B. R., Dall'Agnese, A., Young, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomolecular+condensates+in+the+nucleus.">Biomolecular condensates in the nucleus.</a> Trends in Biochemical Sciences. , 1-17 (2020).</li><li>Strom, A. 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=Phase+separation+drives+heterochromatin+domain+formation.">Phase separation drives heterochromatin domain formation.</a> Nature. 547 (7662), 241-245 (2017).</li><li>Larson, A. G., 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=Liquid+droplet+formation+by+HP1&#945;+suggests+a+role+for+phase+separation+in+heterochromatin.">Liquid droplet formation by HP1&#945; suggests a role for phase separation in heterochromatin.</a> Nature. 547 (7662), 236-240 (2017).</li><li>Boija, 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=Transcription+factors+activate+genes+through+the+phase-separation+capacity+of+their+activation+domains.">Transcription factors activate genes through the phase-separation capacity of their activation domains.</a> Cell. 175 (7), 1842-1855 (2018).</li><li>Hur, W., 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=CDK-Regulated+phase+separation+seeded+by+histone+genes+ensures+precise+growth+and+function+of+histone+locus+bodies.">CDK-Regulated phase separation seeded by histone genes ensures precise growth and function of histone locus bodies.</a> Developmental Cell. 54 (3), 379-394 (2020).</li><li>McSwiggen, D. T., Mir, M., Darzacq, X., Tjian, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluating+phase+separation+in+live+cells:+diagnosis,+caveats,+and+functional+consequences.">Evaluating phase separation in live cells: diagnosis, caveats, and functional consequences.</a> Genes &amp; Development. 33 (23-24), 1619-1634 (2019).</li><li>Peng, A., Weber, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+for+and+against+liquid-liquid+phase+separation+in+the+nucleus.">Evidence for and against liquid-liquid phase separation in the nucleus.</a> Non-coding RNA. 5 (4), (2019).</li><li>Erdel, 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=Mouse+heterochromatin+adopts+digital+compaction+states+without+showing+hallmarks+of+HP1-driven+liquid-liquid+phase+separation.">Mouse heterochromatin adopts digital compaction states without showing hallmarks of HP1-driven liquid-liquid phase separation.</a> Molecular Cell. 78 (2), 236-249 (2020).</li><li>Zhang, H., 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=Nuclear+body+phase+separation+drives+telomere+clustering+in+ALT+cancer+cells.">Nuclear body phase separation drives telomere clustering in ALT cancer cells.</a> Molecular Biology of the Cell. 31 (18), 2048-2056 (2020).</li><li>Ballister, E. R., Aonbangkhen, C., Mayo, A. M., Lampson, M. A., Chenoweth, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Localized+light-induced+protein+dimerization+in+living+cells+using+a+photocaged+dimerizer.">Localized light-induced protein dimerization in living cells using a photocaged dimerizer.</a> Nature Communications. 5, 1-9 (2014).</li><li>Yeager, T. 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=Telomerase-negative+immortalized+human+cells+contain+a+novel+type+of+promyelocytic+leukemia+(PML)+body.">Telomerase-negative immortalized human cells contain a novel type of promyelocytic leukemia (PML) body.</a> Cancer Research. 59 (17), 4175-4179 (1999).</li><li>Zhang, J. M., Zou, 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+lengthening+of+telomeres:+From+molecular+mechanisms+to+therapeutic+outlooks.">Alternative lengthening of telomeres: From molecular mechanisms to therapeutic outlooks.</a> Cell and Bioscience. 10 (1), 1-9 (2020).</li><li>Corpet, 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=PML+nuclear+bodies+and+chromatin+dynamics:+catch+me+if+you+can.">PML nuclear bodies and chromatin dynamics: catch me if you can.</a> Nucleic Acids Research. , 1-23 (2020).</li><li>Li, Y., Ma, X., Wu, W., Chen, Z., Meng, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PML+nuclear+body+biogenesis,+carcinogenesis,+and+targeted+therapy.">PML nuclear body biogenesis, carcinogenesis, and targeted therapy.</a> Trends in Cancer. 6 (10), 889-906 (2020).</li><li>Dilley, R. L., Greenberg, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ALTernative+telomere+maintenance+and+cancer.">ALTernative telomere maintenance and cancer.</a> Trends in Cancer. 1 (2), 145-156 (2015).</li><li>Sobinoff, A. P., Pickett, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alternative+lengthening+of+telomeres:+DNA+repair+pathways+converge.">Alternative lengthening of telomeres: DNA repair pathways converge.</a> Trends in Genetics. 33 (12), 921-932 (2017).</li><li>Draskovic, 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=Probing+PML+body+function+in+ALT+cells+reveals+spatiotemporal+requirements+for+telomere+recombination.">Probing PML body function in ALT cells reveals spatiotemporal requirements for telomere recombination.</a> Proceedings of the National Academy of Sciences. 106 (37), 15726 (2009).</li><li>Zhang, J. M., Yadav, T., Ouyang, J., Lan, L., Zou, 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+lengthening+of+telomeres+through+two+distinct+break-induced+replication+pathways.">Alternative lengthening of telomeres through two distinct break-induced replication pathways.</a> Cell Reports. 26 (4), 955-968 (2019).</li><li>Loe, T. K., 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=Telomere+length+heterogeneity+in+ALT+cells+is+maintained+by+PML-dependent+localization+of+the+BTR+complex+to+telomeres.">Telomere length heterogeneity in ALT cells is maintained by PML-dependent localization of the BTR complex to telomeres.</a> Genes and Development. 34 (9-10), 650-662 (2020).</li><li>Potts, P. R., Yu, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+SMC5/6+complex+maintains+telomere+length+in+ALT+cancer+cells+through+SUMOylation+of+telomere-binding+proteins.">The SMC5/6 complex maintains telomere length in ALT cancer cells through SUMOylation of telomere-binding proteins.</a> Nature Structural and Molecular Biology. 14 (7), 581-590 (2007).</li><li>Chung, I., Leonhardt, H., Rippe, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=De+novo+assembly+of+a+PML+nuclear+subcompartment+occurs+through+multiple+pathways+and+induces+telomere+elongation.">De novo assembly of a PML nuclear subcompartment occurs through multiple pathways and induces telomere elongation.</a> Journal of Cell Science. 124 (21), 3603-3618 (2011).</li><li>Shen, T. H., Lin, H. K., Scaglioni, P. P., Yung, T. M., Pandolfi, P. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+mechanisms+of+PML-nuclear+body+formation.">The mechanisms of PML-nuclear body formation.</a> Molecular Cell. 24 (3), 331-339 (2006).</li><li>Shima, H., 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=Activation+of+the+SUMO+modification+system+is+required+for+the+accumulation+of+RAD51+at+sites+of+DNA+damage.">Activation of the SUMO modification system is required for the accumulation of RAD51 at sites of DNA damage.</a> Journal of Cell Science. 126 (22), 5284-5292 (2013).</li><li>Yal&#231;in, Z., Selenz, C., Jacobs, J. 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=Ubiquitination+and+SUMOylation+in+telomere+maintenance+and+dysfunction.">Ubiquitination and SUMOylation in telomere maintenance and dysfunction.</a> Frontiers in Genetics. 8, 1-15 (2017).</li><li>Sarangi, P., Zhao, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SUMO-mediated+regulation+of+DNA+damage+repair+and+responses.">SUMO-mediated regulation of DNA damage repair and responses.</a> Trends in Biochemical Sciences. 40 (4), 233-242 (2015).</li><li>Banani, S. 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=Compositional+control+of+phase-separated+cellular+bodies.">Compositional control of phase-separated cellular bodies.</a> Cell. 166 (3), 651-663 (2016).</li><li>Min, J., Wright, W. E., Shay, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clustered+telomeres+in+phase-separated+nuclear+condensates+engage+mitotic+DNA+synthesis+through+BLM+and+RAD52.">Clustered telomeres in phase-separated nuclear condensates engage mitotic DNA synthesis through BLM and RAD52.</a> Genes and Development. 33 (13-14), 814-827 (2019).</li><li>Song, J., Durrin, L. K., Wilkinson, T. A., Krontiris, T. G., Chen, Y. <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+a+SUMO-binding+motif+that+recognizes+SUMO-modified+proteins.">Identification of a SUMO-binding motif that recognizes SUMO-modified proteins.</a> Proceedings of the National Academy of Sciences of the United States of America. 101 (40), 14373-14378 (2004).</li><li>Zhang, H., Chenoweth, D. M., Lampson, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chapter+7+-+Optogenetic+control+of+mitosis+with+photocaged+chemical+dimerizers.">Chapter 7 - Optogenetic control of mitosis with photocaged chemical dimerizers.</a> Mitosis and Meiosis Part A. 144, 157-164 (2018).</li><li>Zhang, H., 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=Optogenetic+control+of+kinetochore+function.">Optogenetic control of kinetochore function.</a> Nature Chemical Biology. 13 (10), 1096-1101 (2017).</li><li>Cho, N. W., Dilley, R. L., Lampson, M. A., Greenberg, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interchromosomal+homology+searches+drive+directional+ALT+telomere+movement+and+synapsis.">Interchromosomal homology searches drive directional ALT telomere movement and synapsis.</a> Cell. 159 (1), 108-121 (2014).</li><li>Dilley, R. L., 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=Break-induced+telomere+synthesis+underlies+alternative+telomere+maintenance.">Break-induced telomere synthesis underlies alternative telomere maintenance.</a> Nature. 539 (7627), 54-58 (2016).</li><li>Aonbangkhen, C., Zhang, H., Wu, D. Z., Lampson, M. A., Chenoweth, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reversible+control+of+protein+localization+in+living+cells+using+a+photocaged-photocleavable+chemical+dimerizer.">Reversible control of protein localization in living cells using a photocaged-photocleavable chemical dimerizer.</a> Journal of the American Chemical Society. 140 (38), 11926-11930 (2018).</li><li>Shin, 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=Spatiotemporal+control+of+intracellular+phase+transitions+using+light-activated+optoDroplets.">Spatiotemporal control of intracellular phase transitions using light-activated optoDroplets.</a> Cell. 168 (1-2), 159-171 (2017).</li><li>Shin, 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=Liquid+nuclear+condensates+mechanically+sense+and+restructure+the+genome.">Liquid nuclear condensates mechanically sense and restructure the genome.</a> Cell. 175 (6), 1481-1491 (2018).</li><li>Xiang, X., 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=CRISPR/Cas9-mediated+gene+tagging:+a+step-by-step+protocol.">CRISPR/Cas9-mediated gene tagging: a step-by-step protocol.</a> Methods in Molecular Biology. 1961, 255-269 (2019).</li></ol>

This protocol demonstrated the formation and dissolution of condensates on telomeres with a chemical dimerization system. Kinetics of phase separation and droplet-fusion-induced telomere clustering are monitored with live imaging. Condensate localization and composition are determined with DNA FISH and protein IF.&#160;
There are two critical steps in this protocol. The first is to determine protein and dimerizer concentration. The success in inducing local phase separation at a genomic locus ...

Many proteins and nucleic acids undergo liquid-liquid phase separation (LLPS) and self-assemble into biomolecular condensates to organize biochemistry in cells1,2. LLPS of chromatin-binding proteins leads to the formation of condensates that are associated with specific genomic loci and are implicated in various local chromatin functions3. For example, LLPS of HP1 protein underlies the formation of heterochromatin domains to organize the genome4,5, LLPS of transcription factors forms transcription centers to regulate transcription6, &#65279; LLPS of nascent mRNAs and multi-sex combs protein generates histone locus bodies to regulate the transcription and processing of histone mRNAs7. &#160;However, despite many examples of chromatin-associated condensates being discovered, the underlying mechanisms of condensate formation, regulation and function remain poorly understood. In particular, not all chromatin-associated condensates are formed through LLPS and careful evaluations of condensate formation in live cells are still needed8,9. For example, &#65279; HP1 protein in mouse is shown to have only a weak capacity to form liquid droplets in live cells and &#65279;heterochromatin foci behave as collapsed polymer globules10. Therefore, tools to induce de novo condensates on chromatin in living cells are desirable, particularly those that allow the use of live imaging and biochemical assays to monitor the kinetics of condensate formation, the physical and chemical properties of the resulting condensates, and the cellular consequences of condensate formation.
This protocol reports a chemical dimerization system to induce protein condensates on chromatin11 (Figure 1A). The dimerizer consists of two linked protein-interacting ligands: trimethoprim (TMP) and Halo ligand and can dimerize proteins fused to the cognate receptors: Escherichia coli dihydrofolate reductase (eDHFR) and a bacterial alkyldehalogenase enzyme (Halo enzyme), respectively12. The interaction between Halo ligand and Halo enzyme is covalent, allowing &#160;Halo enzyme to be used as an anchor by fusing it to a chromatin-binding protein to recruit a phase-separating protein fused to eDHFR to chromatin. After the initial recruitment, increased local concentration of the phase separating protein passes the critical concentration needed for phase separation and thus nucleates a condensate at the anchor (Figure 1B). By fusing fluorescent proteins (e.g. mCherry and eGFP) to eDHFR and Halo, nucleation and growth of condensates can be visualized in real time with fluorescence microscopy. Because the interaction between eDHFR and TMP is non-covalent, excess free TMP can be added to compete with the dimerizer for eDHFR binding. This will then release the phase separation protein from the anchor and dissolve the chromatin-associated condensate.
We used this tool to induce de novo promyelocytic leukemia (PML) nuclear body formation on telomeres in telomerase-negative cancer cells that use an alternative lengthening of telomeres&#160;(ALT) pathway for telomere maintenance13,14. &#160;PML nuclear bodies are membrane-less compartments involved in many nuclear processes15,16 and are uniquely localized to ALT telomeres to form APBs, for ALT telomere-associated PML bodies17,18. Telomeres cluster within APBs, presumably to provide repair templates for homology-directed telomere DNA synthesis in ALT19. Indeed, telomere DNA synthesis has been detected in APBs and APBs play essential roles in enriching DNA repair factors on telomeres20,21. However, the mechanisms underlying APB assembly and telomere clustering within APBs were unknown. Since telomere proteins in ALT cells are uniquely modified by small ubiquitin-like modifier (SUMOs)22, many APB components contain sumoylation sites 22,23,24,25 and/or SUMO-interacting motifs (SIMs)26,27 and SUMO-SIM interactions drive phase separation28, we hypothesized that sumoylation on telomeres leads to enrichment of SUMO/SIM containing proteins and SUMO-SIM interactions between those proteins lead to phase separation. &#160;PML protein, which has three sumoylation sites and one SIM site, can be recruited to sumoylated telomeres to form APBs and coalescence of liquid APBs leads to telomeres clustering. To test this hypothesis, we used the chemical dimerization system to mimic sumoylation-induced APB formation by recruiting SIM to telomeres (Figure 2A)11. GFP is fused to Haloenzyme for visualization and to the telomere-binding protein TRF1 to anchor the dimerizer to telomeres. SIM is fused to eDHFR and mCherry. Kinetics of condensate formation and droplet fusion-induced telomere clustering are followed with live cell imaging. &#160;Phase separation is reversed by adding excess free TMP to compete with eDHFR binding. Immunofluorescence (IF) and fluorescence in situ hybridization (FISH) are used to determine condensate composition and telomeric association. Recruiting SIM enriches SUMO on telomeres and the induced condensates contain PML and therefore are APBs. Recruiting a SIM mutant that cannot interact with SUMO does not enrich SUMO on telomeres or induce phase separation, indicating that the fundamental driving force for APB condensation is SUMO-SIM interaction. Agreeing with this observation, polySUMO-polySIM polymers that fused to a TRF2 binding factor RAP1 can also induce APB formation29. Compared to the polySUMO-polySIM fusion system where phase separation occurs as long as enough proteins are produced, the chemical dimerization approach presented here induces phase separation on demand and thus offers better temporal resolution to monitor the kinetics of phase separation and telomere clustering process. In addition, this chemical dimerization system permits the recruitment of other proteins to assess their ability in inducing phase separation and telomere clustering. For example, a disordered protein recruited to telomeres can also form droplets and cluster telomeres without inducing APB formation, suggesting telomere clustering is independent of APB chemistry and only relies on APB liquid property11.&#160;

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr >
			<td >0.25% Trypsin, 0.1% EDTA in HBSS w/o Calcium, Magnesium and Sodium Bicarbonate</td>
			<td >Corning</td>
			<td >MT25053CI</td>
			<td ></td>
		</tr>
		<tr >
			<td >16% Formaldehyde (w/v), Methanol-free</td>
			<td >Thermo Scientific</td>
			<td >28906</td>
			<td >Prepare 1% in 1x PBS</td>
		</tr>
		<tr >
			<td >6 Well Culture Plate</td>
			<td >VWR</td>
			<td >10861-554</td>
			<td ></td>
		</tr>
		<tr >
			<td >Aluminum Foil</td>
			<td >Fisher Scientific</td>
			<td >01-213-101</td>
			<td ></td>
		</tr>
		<tr >
			<td >Anti-mCherry antibody</td>
			<td >Abcam</td>
			<td >Ab183628</td>
			<td ></td>
		</tr>
		<tr >
			<td >Anti-PML antibody</td>
			<td >Santa Cruz</td>
			<td >sc966</td>
			<td ></td>
		</tr>
		<tr >
			<td >Anti-SUMO1 antibody</td>
			<td >Abcam</td>
			<td >Ab32058</td>
			<td ></td>
		</tr>
		<tr >
			<td >Anti-SUMO2/3 antibody</td>
			<td >Cytoskeleton</td>
			<td >Asm23</td>
			<td ></td>
		</tr>
		<tr >
			<td >Blocking Reagent</td>
			<td >Roche</td>
			<td >11096176001</td>
			<td ></td>
		</tr>
		<tr >
			<td >Bovine Serum Albumin (BSA)</td>
			<td >Fisher Scientific</td>
			<td >BP9706100</td>
			<td ></td>
		</tr>
		<tr >
			<td >BTX Tube micro 1.5ML&#160;</td>
			<td >VWR</td>
			<td >89511-258</td>
			<td ></td>
		</tr>
		<tr >
			<td >Circle Cover Slips</td>
			<td >Thermo Scientific</td>
			<td >3350</td>
			<td ></td>
		</tr>
		<tr >
			<td >Confocal microscope&#160;</td>
			<td >Nikon</td>
			<td >MQS31000</td>
			<td ></td>
		</tr>
		<tr >
			<td >DAPI</td>
			<td >Fisher Scientific</td>
			<td >D1306</td>
			<td></td>
		</tr>
		<tr >
			<td >Dimethyl Sulphoxide&#160;</td>
			<td >Sigma-Aldrich</td>
			<td >472301</td>
			<td ></td>
		</tr>
		<tr >
			<td >DMEM with L-Glutamine, 4.5g/L Glucose and Sodium Pyruvate</td>
			<td >Corning</td>
			<td >MT10017CV</td>
			<td ></td>
		</tr>
		<tr >
			<td >EMCCD Camera</td>
			<td >iXon Life&#160;</td>
			<td >897</td>
			<td ></td>
		</tr>
		<tr >
			<td >Ethanol</td>
			<td >Fisher Scientific</td>
			<td >4355221</td>
			<td ></td>
		</tr>
		<tr >
			<td >Fetal Bovine Serum, Qualified, USDA-approved Regions</td>
			<td >Gibco</td>
			<td >A4766801</td>
			<td ></td>
		</tr>
		<tr >
			<td >Formamide, Deionized</td>
			<td >MilliporeSigma</td>
			<td >46-101-00ML</td>
			<td ></td>
		</tr>
		<tr >
			<td >Goat anti-Mouse IgG (H+L), Recombinant Secondary Antibody, Alexa Fluor 647</td>
			<td >Invitrogen</td>
			<td >A28181</td>
			<td ></td>
		</tr>
		<tr >
			<td >Goat anti-Rabbit IgG (H+L), Recombinant Secondary Antibody, Alexa Fluor 647</td>
			<td >Invitrogen</td>
			<td >A32733</td>
			<td ></td>
		</tr>
		<tr >
			<td >High Precision Straight Tapered Ultra Fine Point Tweezers/Forceps</td>
			<td >Fisher Scientific</td>
			<td >12-000-122</td>
			<td ></td>
		</tr>
		<tr >
			<td >Laser merge module&#160;</td>
			<td >Nikon</td>
			<td >NIIMHF47180</td>
			<td ></td>
		</tr>
		<tr >
			<td >Leibovitz&#39;s L-15 Medium</td>
			<td >Gibco</td>
			<td >21083027</td>
			<td ></td>
		</tr>
		<tr >
			<td >Lipofectamine 2000 Transfection Reagent</td>
			<td >Invitrogen</td>
			<td >11668027</td>
			<td ></td>
		</tr>
		<tr >
			<td >Figure plotting software, MATLAB</td>
			<td >The MathWorks</td>
			<td ></td>
			<td ></td>
		</tr>
		<tr >
			<td >Microscope Slide Box</td>
			<td >Fisher Scientific</td>
			<td >34487</td>
			<td ></td>
		</tr>
		<tr >
			<td >Nail Polish</td>
			<td >Fisher Scientific</td>
			<td >50-949-071</td>
			<td ></td>
		</tr>
		<tr >
			<td >Imaging software, NIS-Elements&#160;</td>
			<td >Nikon</td>
			<td ></td>
			<td ></td>
		</tr>
		<tr >
			<td >Opti-MEM Reduced Serum Media</td>
			<td >Gibco</td>
			<td >51985091</td>
			<td ></td>
		</tr>
		<tr >
			<td >Parafilm</td>
			<td >Bemis</td>
			<td >13-374-12</td>
			<td></td>
		</tr>
		<tr >
			<td >PBS 10x, pH 7.4</td>
			<td >Fisher Scientific</td>
			<td >70-011-044</td>
			<td ></td>
		</tr>
		<tr >
			<td >Penicillin-Streptomycin Solution,100X</td>
			<td >Gibco</td>
			<td >15140122</td>
			<td ></td>
		</tr>
		<tr >
			<td >Piezo Z-Drive&#160;</td>
			<td >Physik Instrumente (PI)</td>
			<td >91985</td>
			<td ></td>
		</tr>
		<tr >
			<td >Pipet Tips</td>
			<td >VWR</td>
			<td >10017</td>
			<td ></td>
		</tr>
		<tr >
			<td >Plain and Frosted Clipped Corner Microscope Slides</td>
			<td >Fisher Scientific</td>
			<td >22-037-246</td>
			<td ></td>
		</tr>
		<tr >
			<td >Poly-D-Lysine solution</td>
			<td >Sigma-Aldrich</td>
			<td >A-003-E</td>
			<td></td>
		</tr>
		<tr >
			<td >Sodium Azide</td>
			<td >Fisher Scientific</td>
			<td >BP922I-500</td>
			<td ></td>
		</tr>
		<tr >
			<td >Spinning disk</td>
			<td >Yokogawa</td>
			<td >CSU-X1</td>
			<td ></td>
		</tr>
		<tr >
			<td >Square Cover Slips</td>
			<td >Thermo Scientific</td>
			<td >3305</td>
			<td ></td>
		</tr>
		<tr >
			<td >TBS 10x solution</td>
			<td >Fisher Scientific</td>
			<td >BP2471500</td>
			<td ></td>
		</tr>
		<tr >
			<td >TelC-Alexa488</td>
			<td >PNA Bio</td>
			<td >F1004</td>
			<td ></td>
		</tr>
		<tr >
			<td >TMP</td>
			<td >Synthesized by Chenoweth lab</td>
			<td ></td>
			<td >Available upon request</td>
		</tr>
		<tr >
			<td >TNH</td>
			<td >Synthesized by Chenoweth lab</td>
			<td ></td>
			<td >Available upon request</td>
		</tr>
		<tr >
			<td >Tris Solution</td>
			<td >Fisher Scientific</td>
			<td >92-901-00ML</td>
			<td></td>
		</tr>
		<tr >
			<td >Triton X-100 10% Solution</td>
			<td >MilliporeSigma</td>
			<td >64-846-350ML</td>
			<td >Prepare 0.5% in 1x PBS</td>
		</tr>
		<tr >
			<td >U2Os cell line</td>
			<td >From E.V. Makayev lab (Nanyang Technological University, Singapore)</td>
			<td >HTB-96</td>
			<td ></td>
		</tr>
		<tr >
			<td >VECTASHIELD Antifade Mounting Medium</td>
			<td >Vector Laboratories</td>
			<td >NC9524612</td>
			<td ></td>
		</tr>
	</tbody>
</table>

chemical dimerization-induced protein condensates on telomeres

Chromatin-associated condensates are implicated in many nuclear processes, but the underlying mechanisms remain elusive. This protocol describes a chemically-induced protein dimerization system to create condensates on telomeres. The chemical dimerizer consists of two linked ligands that can each bind to a protein: Halo ligand to Halo-enzyme and trimethoprim (TMP) to E. coli dihydrofolate reductase (eDHFR), respectively. Fusion of Halo enzyme to a telomere protein anchors dimerizers to telomeres through covalent Halo ligand-enzyme binding. Binding of TMP to eDHFR recruits eDHFR-fused phase separating proteins to telomeres and induces condensate formation. Because TMP-eDHFR interaction is non-covalent, condensation can be reversed by using excess free TMP to compete with the dimerizer for eDHFR binding. An example of inducing promyelocytic leukemia (PML) nuclear body formation on telomeres and determining condensate growth, dissolution, localization and composition is shown. This method can be easily adapted to induce condensates at other genomic locations by fusing Halo to a protein that directly binds to the local chromatin or to dCas9 that is targeted to the genomic locus with a guide RNA. By offering the temporal resolution required for single cell live imaging while maintaining phase separation in a population of cells for biochemical assays, this method is suitable for probing both the formation and function of chromatin-associated condensates.

Representative images of telomeric localization of SUMO identified by telomere DNA FISH and SUMO protein IF are shown in Figure 2. Cells with SIM recruitment enriched SUMO1 and SUMO 2/3 on telomeres compared to cells with SIM mutant recruitment. This indicates that SIM dimerization-induced SUMO enrichment on telomeres depends on SUMO-SIM interactions.
A representative time lapse movie of TRF1 and SIM after dimerization is shown in Video 1. Snapsho...

Watch this Scientific Journal Video about Chemical Dimerization-Induced Protein Condensates on Telomeres at JoVE.com

Chemical Dimerization-Induced Protein Condensates on Telomeres

This protocol illustrates a chemically induced protein dimerization system to create condensates on chromatin.&#160; The formation of promyelocytic leukemia (PML) nuclear body on telomeres with chemical dimerizers is demonstrated. Droplet growth, dissolution, localization and composition are monitored with live cell imaging, immunofluorescence (IF) and fluorescence in situ hybridization (FISH).

Chromatin-associated condensates are implicated in many nuclear processes, but the underlying mechanisms remain elusive. This protocol describes a ...

This protocol describes the chemical dimerization system to induce protein condensates on telomeres. It can be easily adapted to induce condensates on other genomic loci, and is suitable for probing the formation and function of chromatin associated condensates. This method offers temporal resolution required for live cell imaging and maintains phase separation in the population of cells for biochemical assays.To begin, dissolve dimerizers in DMSO at 10 millimolar and store them in plastic microcentrifuge tubes at minus 80 degrees Celsius for long-term storage. Dilute an aliquot of 10 millimolar dimerizer in imaging medium to a stock concentration of 10 micromolar and store it at minus 20 degrees Celsius. When ready to use, dilute dimerizers to a final working concentration of 100 nanomolar in growth medium or imaging medium.Seed 10 to the fifth cells in 12 millimeter diameter circular cover glasses coated with Poly-D-Lysine in a six-well plate. Then transfect the cells with the Halo-GFP-TRF1 and mCherry-eDHFR-SIM or mCherry-eDFR-SIM mutant plasmids and wait for 24 to 48 hours before proceeding to immunofluorescence. Add the diluted 100 nanomolar dimerizers to the cells and incubate them in 37 degrees Celsius for four to five hours.After the incubation, fix the cells in PBS solution containing 4%formaldehyde and 0.1%Triton X-100 for 10 minutes at room temperature to permeabilize the cells. Then wash the cells three times with PBS. Wash cover slips twice with 50 microliters of TBS-Tx and once with 50 microliters of antibody dilution buffer.Incubate each cover slip with 50 microliters of primary anti-PML, anti-SUMO-1, or anti-SUMO-2 and 3 antibody at four degrees Celsius in a humidified chamber overnight. Wash cover slips three times with antibody dilution buffer to remove unbound primary antibody, then incubate the cells with secondary antibody for one hour in a dark box at room temperature. After staining, wash cover slips three times with TBS-Tx.Label slides by adding two microliters of one microgram per milliliter DAPI, then flip the cover slips over and place them onto the DAPI drop. Aspirate extra fluid from the edge of the cover slip. Seal the slide with nail polish, allow it to dry, and rinse the top of the cover slip with water.Place the slides in the freezer until imaging. Seed 10 to the fifth cells on 12 millimeter circular cover glasses coated with Poly-D-Lysine in a six-well plate and transfect them with Halo-TRF1 and mCherry-eDHFR-SIM or mCherry-eDHFR-SIM mutant plasmids. Fix the cells with 4%formaldehyde for 10 minutes at room temperature and wash them four times with PBS.For IF-FISH, stain the cells with primary and secondary antibodies and refix them with 4%formaldehyde for 10 minutes at room temperature, then wash them four times with PBS and dehydrate the cover slips in an ethanol series. Incubate the cover slips with the 488 telomere C-PNA probe in five microliters of hybridization solution at 75 degrees Celsius for five minutes, then incubate the cover slips overnight in a humidified chamber at room temperature. Wash the cover slips three times with wash buffer for two minutes per wash at room temperature and mount them with one microgram per milliliter DAPI in mounting media for imaging.For live imaging, mount the cover slips in magnetic chambers on a heated stage in an environmental chamber, maintaining the cells in one milliliter of imaging medium without phenol red. Set up the microscope and environmental control apparatus as described in the text manuscript. Locate cells with a bright GFP signal on the telomeres and diffusive mCherry signal in the cytosol.Find around 20 cells, memorizing each position with the XYZ information, and set up parameters for time-lapse imaging. Use 0.5 micrometer spacing for a total of eight micrometers in Z and five minute time interval for two to four hours for both GFP and mCherry channels. Use 30%of 594 nanometer and 50%of 488 nanometer power intensity, with exposure times of 200 milliseconds and a camera gain of 300.Start imaging and take one time loop as pre-dimerization. Then pause imaging, add 0.5 milliliters of imaging media containing 15 microliters of 10 micromolar dimerizer to the imaging chamber, taking care not to touch the stage, and resume imaging. When ready to reverse dimerization, pause imaging and add 0.5 milliliters of imaging media containing two microliters of 100 millimolar stock TMP to the imaging chamber.Continue imaging the cells for one to two hours. For fixed imaging, use the same microscope setup as live imaging, but without the stage heating. Locate around 30 to 50 cells with the red signal to select for transfected cells.Acquire images with 0.3 micrometer spacing for a total of eight micrometers in Z.Use 80%of 647 nanometer, 80%of 561 nanometer, and 70%of 488 nanometer power intensity, with exposure times of 600 milliseconds and a camera gain of 300. Telomeric localization of SUMO was identified using telomere DNA FISH and SUMO protein immunofluorescence. Cells with SIM recruitment enriched SUMO-1 and SUMO-2 and 3 compared to cells with SIM mutant recruitment, indicating that SIM dimerization induced SUMO enrichment on telomeres depends on SUMO-SIM interactions.A time-lapse movie of TRF-1 and SIM after dimerization is shown here. SIM was successfully recruited to telomeres, and both SIM and TRF-1 foci became larger and brighter, as predicted for liquid droplet formation and growth. In addition, fusion of TRF-1 foci was observed, which led to telomere clustering, as shown in the reduced telomere number and increased telomere intensity over time.In contrast, SIM mutant was recruited to telomeres after dimerization, but did not induce any droplet formation or telomere clustering, indicating that phase separation and telomere clustering is driven by SUMO-SIM interactions. The reversal of phase separation and telomere clustering was observed after adding excess free TMP. Telomere number increased and telomere intensity decreased over time.Representative images of APBs identified by telomere DNA FISH and PML protein IF are shown here. Cells with SIM recruited have more APBs than cells with SIM mutant recruited, suggesting dimerization induced condensates are indeed APBs. When performing this protocol, do not expose light sensitive dimerizers to light.Work in a dark room with a lamp that emits red light and wrap cells with aluminum foil during incubation. Following this procedure, proximity labeling can be used to generate a comprehensive list of components in the induced condensate. Live imaging can be used to follow the dynamics of components in the condensate.These methods can help determine the roles of governing condensate composition control.

Research

JoVE Journal

Biology

Staining of Proteins in Gels with Coomassie G-250 without Organic Solvent and Acetic Acid

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents ...

Using the GELFREE 8100 Fractionation System for Molecular Weight-Based Fractionation with Liquid Phase Recovery

The GELFREE 8100 Fractionation System is a novel protein fractionation system designed to maximize protein recovery during molecular weight based ...

In-vivo Detection of Protein-protein Interactions on Micro-patterned Surfaces

In-vivo Detection of Protein-protein Interactions on Micro-patterned Surfaces

Unraveling the interaction network of molecules in-vivo is key to understanding the mechanisms that regulate cell function and metabolism. A multitude of ...

Visualization of Mitochondrial Respiratory Function using Cytochrome C Oxidase / Succinate Dehydrogenase (COX/SDH) Double-labeling Histochemistry

Visualization of Mitochondrial Respiratory Function using Cytochrome C Oxidase / Succinate Dehydrogenase COX/SDH Double-labeling Histochemistry

Mitochondrial DNA (mtDNA) defects are an important cause of disease and may underlie aging and aging-related alterations 1,2. The mitochondrial theory of ...

A Protocol for the Identification of Protein-protein Interactions Based on 15N Metabolic Labeling, Immunoprecipitation, Quantitative Mass Spectrometry and Affinity Modulation

A Protocol for the Identification of Protein-protein Interactions Based on 15N Metabolic Labeling, Immunoprecipitation, Quantitative Mass Spectrometry and Affinity Modulation

Protein-protein interactions are fundamental for many biological processes in the cell. Therefore, their characterization plays an important role in ...

Protein WISDOM: A Workbench for In silico De novo Design of BioMolecules

Protein WISDOM: A Workbench for In silico De novo Design of BioMolecules

The aim of de novo protein design is to find the amino acid sequences that will fold into a desired 3-dimensional structure with improvements in specific ...

Genetically-encoded Molecular Probes to Study G Protein-coupled Receptors

To facilitate structural and dynamic studies of G protein-coupled receptor (GPCR) signaling complexes, new approaches are required to introduce ...

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

The production of recombinant membrane proteins for structural and functional studies remains technically challenging due to low levels of expression and ...

High-throughput Screening for Protein-based Inheritance in S. cerevisiae

High-throughput Screening for Protein-based Inheritance in S. cerevisiae

The encoding of biological information that is accessible to future generations is generally achieved via changes to the DNA sequence. Long-lived ...

Combining Chemical Cross-linking and Mass Spectrometry of Intact Protein Complexes to Study the Architecture of Multi-subunit Protein Assemblies

Proteins interact with their ligands to form active and dynamic assemblies which carry out various cellular functions. Elucidating these interactions is ...