We thank Laurie Lee for critical reading of the manuscript. T.W.C is supported by an American Heart Association Predoctoral Fellowship (12PRE6590007). M.R.B. is supported by a National Cancer Institute training grant (T32 CA119925). S.S.H is supported by National Institutes of Health (R01DK078640). E.L. is supported by the National Institutes of Health (R01GM081635 and R01GM103926).

1. Preparation of Xenopus&#160;Egg Extract
NOTE: Each frog yields approximately 1 ml&#160;of usable egg extract. Extracts from 10 frogs are typically prepared at one time, and the volume of buffer described below is for performing a 10 frog Xenopus egg extract prep. The buffer volume can be adjusted accordingly for larger or smaller preparations of egg extract. Preps generated in this manner consistently yield protein concentrations &#8805; 50 mg/ml. The process of collecting e...

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The authors declare that they have no competing financial interests.

Xenopus egg extract is a robust biochemical system for investigating &#946;-catenin turnover. The concentration of &#946;-catenin in Xenopus egg extract is ~25 nM&#160;2. Under optimal conditions, the egg extract is capable of degrading &#946;-catenin at a rate of 50-100 nM/hr and is half-maximal at 200 nM24. There are several critical steps for successful reconstitution of &#946;-catenin degradation using Xenopus egg extract. These include 1) generating high quality X...

A correction was made to <a href="http://www.jove.com/video/51425">Reconstitution Of &#946;-catenin Degradation In Xenopus Egg Extract</a>. At the time of publication there were some instances where an incorrect volume notation was used. These instances were corrected from:
2.1.2. Add extract to 1/10 the volume of pelleted antibody or affinity beads (e.g., 20 ml pelleted beads to 200 ml extract). In order to minimize dilution of the extract, withdraw as much liquid from the beads as possible before addition of the extract using gel loading tips with long, tapered tips.
2.2.5. Aliquot the appropriate volumes for degradation assay into pre-chilled microfuge tubes on ice. For radiolabeled &#946;-catenin degradation assays, withdraw 2-5 ml extract for each time point.
3.2.3. At the designated time point, remove 1-5 ml of the sample and mix immediately with SDS sample buffer (5x volume) to stop the reaction. To make sure the degradation reaction is completely terminated, flick tube several times and vortex vigorously.
3.2.4. Perform SDS-PAGE/autoradiography. Run 1 ml equivalents (~50 mg of protein) of the extract for each time point/lane. Degradation of &#946;-catenin in Xenopus egg extract should be evidenced by the time-dependent decrease in intensity of the radiolabeled &#946;-catenin band Figure 2. Quantify results using ImageJ, ImageQuant, or other preferred imaging software if necessary.
4.2.2. Add in vitro-translated &#946;-catenin-luciferase fusion (from 4.1) into prepared Xenopus reaction mix (from 2.2) on ice and mix well as in 3.2.1. NOTE: The activity of the &#946;-catenin luciferase that is added to the extract is typically between 20 - 50,000 relative luminescence units (RLU)/ml of extract (based on measurements obtained from 4.1.2). Starting signal should be approximately 100,000 RLU (2-5 ml of the in vitro-translated &#946;-catenin-luciferase fusion).
to:
2.1.2. Add extract to 1/10 the volume of pelleted antibody or affinity beads (e.g., 20 &#181;l pelleted beads to 200 &#181;l extract). In order to minimize dilution of the extract, withdraw as much liquid from the beads as possible before addition of the extract using gel loading tips with long, tapered tips.
2.2.5. Aliquot the appropriate volumes for degradation assay into pre-chilled microfuge tubes on ice. For radiolabeled &#946;-catenin degradation assays, withdraw 2-5 &#181;l extract for each time point.
3.2.3. At the designated time point, remove 1-5 &#181;l of the sample and mix immediately with SDS sample buffer (5x volume) to stop the reaction. To make sure the degradation reaction is completely terminated, flick tube several times and vortex vigorously.
3.2.4. Perform SDS-PAGE/autoradiography. Run 1 &#181;l equivalents (~50 mg of protein) of the extract for each time point/lane. Degradation of &#946;-catenin in Xenopus egg extract should be evidenced by the time-dependent decrease in intensity of the radiolabeled &#946;-catenin band Figure 2. Quantify results using ImageJ, ImageQuant, or other preferred imaging software if necessary.
4.2.2. Add in vitro-translated &#946;-catenin-luciferase fusion (from 4.1) into prepared Xenopus reaction mix (from 2.2) on ice and mix well as in 3.2.1. NOTE: The activity of the &#946;-catenin luciferase that is added to the extract is typically between 20 - 50,000 relative luminescence units (RLU)/&#181;l of extract (based on measurements obtained from 4.1.2). Starting signal should be approximately 100,000 RLU (2-5 &#181;l of the in vitro-translated &#946;-catenin-luciferase fusion).

Erratum: Reconstitution Of &#946;-catenin Degradation In Xenopus Egg Extract

Xenopus laevis egg extract has been used extensively to study many cell biological processes including cytoskeletal dynamics, nuclear assembly and import, apoptosis, ubiquitin metabolism, cell cycle progression, signal transduction, and protein turnover1-17. The Xenopus egg extract system is amenable to the biochemical analysis of a legion of cellular processes because egg extract represents essentially undiluted cytoplasm that contains all the essential cytoplasmic components necessary to execute these processes and enable investigation. Large quantities of egg extract can be prepared at one time for biochemical manipulations that require large amounts of material (e.g., protein purification or high-throughput screening)18-20. Another advantage is that the concentration of specific proteins in Xenopus egg extract can be precisely adjusted by addition of recombinant protein and/or immunodepletion of endogenous proteins in contrast to transfection of plasmid DNA where expression of the protein of interest is difficult to control. In addition, the lack of available recombinant proteins can be overcome by the addition of transcripts encoding the protein of interest, taking advantage of the freshly prepared Xenopus egg extract&#8217;s high capacity to translate exogenously added mRNA.
The regulation of protein degradation is critical for the control of many cellular pathways and processes21. Xenopus egg extract has been used extensively to study protein degradation as the system allows for multiple ways to monitor protein turnover without confounding influences of transcription and translation. The Wnt signaling pathway is a highly conserved signaling pathway that plays critical roles in development and disease. The turnover of &#946;-catenin, the major effector of the Wnt pathway, is highly regulated, and an increased steady-state level of &#946;-catenin is critical for the activation of Wnt target genes. The importance of &#946;-catenin degradation is highlighted by the fact that mutations in the Wnt pathway that inhibit &#946;-catenin degradation found in ~90% of all sporadic cases of colorectal cancer22. &#946;-catenin degradation by components of the Wnt pathway can be faithfully recapitulated in Xenopus egg extract to study the mechanism of its turnover as well as to identify novel small molecule modulators of its degradation2,19,20,23-29 .
Methods for the preparation of Xenopus egg extract for studying the cell cycle have been described in previous JoVE publications30-32. The current protocol describes a modification of these methods and is optimized for the degradation of [35S]-radiolabeled &#946;-catenin and luciferase-tagged &#946;-catenin in Xenopus egg extract. The radiolabeled degradation assay allows for direct visualization of protein levels via autoradiography. [35S]methionine is incorporated into the protein of interest using an in vitro translation reaction that can then be directly added to a degradation reaction. In addition, the radiolabeled protein turnover assay does not require an antibody against the protein of interest or an epitope tag, which can influence protein stability. Because even small changes in protein levels, as reflected in changes in the intensity of the radiolabeled protein band, are readily visualized by autoradiography, the [35S]-radiolabeled degradation assay represents a very useful method for visualization of protein turnover2.
Fusion of &#946;-catenin to firefly luciferase (hereafter referred to as simply &#34;luciferase&#34;) allows for precise and facile quantitative measurements of protein levels, in order to determine the kinetic properties of &#946;-catenin turnover19,20 . A major advantage of the luciferase assay is that it provides a strong quantitative system that is easily scaled up. The following protocol provides simple methods for assaying &#946;-catenin degradation and a robust, efficient, and effective method for high-throughput screening of novel &#946;-catenin modulators.

<table border="0" cellpadding="0" cellspacing="0" style="width:709px;" width="710">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Name of Reagent/ Material</td>
			<td style="width:132px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:243px;">Comments/Description</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Pregnant Mare Serum Gonadotropin (PMSG)</td>
			<td style="width:132px;">ProSpec</td>
			<td style="width:119px;">hor-272-A</td>
			<td>Reconstituted with distilled water before use.&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Human Chorionic Gonadotropin</td>
			<td style="width:132px;">Sigma</td>
			<td style="width:119px;">CG10-10VL</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Potassium Chloride</td>
			<td style="width:132px;">Fisher</td>
			<td style="width:119px;">BP366-1</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Sodium Chloride</td>
			<td style="width:132px;">Research Products International</td>
			<td style="width:119px;">S23020-5000.0</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Magnesium Chloride</td>
			<td style="width:132px;">Fisher</td>
			<td style="width:119px;">BP214-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Calcium Chloride</td>
			<td style="width:132px;">Acros Organics</td>
			<td style="width:119px;">AC42352-5000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">HEPES</td>
			<td style="width:132px;">Fisher</td>
			<td style="width:119px;">BP310-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Cysteine</td>
			<td style="width:132px;">Acros Organics</td>
			<td style="width:119px;">AC17360-1000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Leupeptin</td>
			<td style="width:132px;">Sigma</td>
			<td style="width:119px;">L2884-10MG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Aprotinin</td>
			<td style="width:132px;">Sigma</td>
			<td style="width:119px;">A1153-10MG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Pepstatin</td>
			<td style="width:132px;">Sigma</td>
			<td style="width:119px;">P4265-5MG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Cytochalasin B</td>
			<td style="width:132px;">Sigma</td>
			<td style="width:119px;">C8273-10MG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">3 mL syringe: Luer Lock tip</td>
			<td style="width:132px;">Becton Dickinson</td>
			<td style="width:119px;">309657</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">27G1 needle</td>
			<td style="width:132px;">Becton Dickinson</td>
			<td style="width:119px;">305109</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">96 well solid white polystyrene microplate, round bottomed</td>
			<td style="width:132px;">Corning</td>
			<td style="width:119px;">3605</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Steady-Glo Luciferase assay system</td>
			<td style="width:132px;">Promega</td>
			<td style="width:119px;">E2520</td>
			<td>Store long-term at -80, can store for up to 1 month at -20</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">TNT Sp6 coupled reticulocyte lysate system</td>
			<td style="width:132px;">Promega</td>
			<td style="width:119px;">L4600</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">TNT Sp6 High-yield Wheat Germ protein expression system</td>
			<td style="width:132px;">Promega</td>
			<td style="width:119px;">L3260</td>
			<td>Generally higher yield than reticulocyte lysate&#160;</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">EasyTag Express Protein Labeling Mix [S35]</td>
			<td style="width:132px;">Perkin Elmer</td>
			<td style="width:119px;">NEG772007MC</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Creatine phosphate</td>
			<td style="width:132px;">Sigma</td>
			<td style="width:119px;">27920-5G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">ATP</td>
			<td style="width:132px;">Sigma</td>
			<td style="width:119px;">A2383-5G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Creatine phosphokinase</td>
			<td style="width:132px;">Sigma</td>
			<td style="width:119px;">C3755-35KU</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Dimethyl Sulfoxide (DMSO)</td>
			<td style="width:132px;">Sigma</td>
			<td style="width:119px;">D8418-50ML</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Dual-Glo luciferase assay system</td>
			<td style="width:132px;">Promega</td>
			<td style="width:119px;">E2920</td>
			<td>Same storage conditions as Steady-Glo</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">50 mL Centrifuge tubes</td>
			<td style="width:132px;">Fisher Scientific</td>
			<td style="width:119px;">0556214D</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sorvall SS-34 fixed angle rotor</td>
			<td style="width:132px;">Thermo Scientific</td>
			<td style="width:119px;">28020</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">115 V 50/60 Hz Minicentrifuge</td>
			<td style="width:132px;">Fisher Scientific</td>
			<td style="width:119px;">05-090-128</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">mMessage mMachine Sp6 kit</td>
			<td style="width:132px;">Ambion</td>
			<td style="width:119px;">AM1340</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Anti-Firefly Luciferase antibody</td>
			<td style="width:132px;">Abcam</td>
			<td style="width:119px;">ab16466</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Anti-GSK3 antibody</td>
			<td style="width:132px;">BD Transduction Laboratories</td>
			<td style="width:119px;">610201</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:132px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:132px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:132px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:132px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Name of Equipment</td>
			<td style="width:132px;">Company</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">FLUOStar Optima</td>
			<td style="width:132px;">BMG Labtech</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sorvall RC-6 Plus Centrifuge</td>
			<td style="width:132px;">Thermo Scientific</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">16&#176;C Incubator</td>
			<td style="width:132px;">Percival Scientific</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

reconstitution of &#946;-catenin degradation in xenopus egg extract

Xenopus laevis egg extract is a well-characterized, robust system for studying the biochemistry of diverse cellular processes. Xenopus egg extract has been used to study protein turnover in many cellular contexts, including the cell cycle and signal transduction pathways1-3. Herein, a method is described for isolating Xenopus egg extract that has been optimized to promote the degradation of the critical Wnt pathway component, &beta;-catenin. Two different methods are described to assess &beta;-catenin protein degradation in Xenopus egg extract. One method is visually informative ([35S]-radiolabeled proteins), while the other is more readily scaled for high-throughput assays (firefly luciferase-tagged fusion proteins). The techniques described can be used to, but are not limited to, assess &beta;-catenin protein turnover and identify molecular components contributing to its turnover. Additionally, the ability to purify large volumes of homogenous Xenopus egg extract combined with the quantitative and facile readout of luciferase-tagged proteins allows this system to be easily adapted for high-throughput screening for modulators of &beta;-catenin degradation.

A schematic of &#946;-catenin degradation in Xenopus egg extract is shown in Figure 2A. 35S-labeled &#946;-catenin was incubated in Xenopus egg extract, aliquots (1 ml extract equivalent) were removed at the appropriate times, and samples were subjected to SDS-PAGE followed by autoradiography. &#946;-catenin degradation by components of the Wnt pathway is mediated by the ubiquitin-proteasome system2, and degradation of [35S]-radiolabeled &#946;-catenin i...

Watch this Scientific Journal Video about Reconstitution Of Î²-catenin Degradation In Xenopus Egg Extract at JoVE.com

Reconstitution Of &amp;#946;-catenin Degradation In Xenopus Egg Extract

A method is described for analyzing protein degradation using radiolabeled and luciferase-fusion proteins in Xenopus egg extract and its adaptation for high-throughput screening for small molecule modulators of protein degradation.

Reconstitution Of &#946;-catenin Degradation In Xenopus Egg Extract

Xenopus laevis egg extract is a well-characterized, robust system for studying the biochemistry of diverse cellular processes. Xenopus egg extract has ...

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12.0K Views.  Vanderbilt University Medical Center. A method is described for analyzing protein degradation using radiolabeled and luciferase-fusion proteins in Xenopus egg extract and its adaptation for high-throughput screening for small molecule modulators of protein degradation.