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  • www.sciencemag.org/cgi/content/full/316/5827/1043/DC1

    Supporting Online Material for

    Wilms Tumor Suppressor WTX Negatively Regulates Wnt/β-Catenin Signaling

    Michael B. Major, Nathan D. Camp, Jason D. Berndt, XianHua Yi, Seth J. Goldenberg, Charlotte Hubbert, Travis L. Biechele, Anne-Claude Gingras, Ning Zheng, Michael J.

    MacCoss, Stephane Angers, Randall T. Moon*

    *To whom correspondence should be addressed. E-mail: [email protected]

    Published 18 May 2007, Science 316, 1043 (2007) DOI: 10.1126/science.1141515

    This PDF file includes

    Materials and Methods SOM Text Figs. S1 to S6 Tables S1 and S2 References

  • Supporting Online Material Materials and Methods Plasmids All expression constructs, including human WTX (AK097146), were created with standard PCR-based cloning strategies. β-catenin(SA) contains alanine substitutions at residues 33, 37, 41 and 45. Detailed descriptions, maps and sequences of the expression plasmids can be found on the Moon Lab website (http://faculty.washington.edu/rtmoon/). The β-catenin activated reporter (pBAR) contains 12 TCF binding sites (5’- AGATCAAAGG-3’) separated by distinct 5 base linkers. These elements are directly upstream of a minimal thymidine kinase promoter which then drives the expression of firefly luciferase. The reporter contains a separate PGK promoter that constitutively drives the expression of a puromycin resistance gene. The reporter is in a lentiviral platform. Tissue culture, transfections and small interfering RNAs HEK293T cells and RKO cells were grown in DMEM supplemented with 10% fetal bovine serum in a 37°C humidified incubator with 5% CO2. Selection and passage of stable cell lines was performed with 2 μg/ml puromycin for 10-14 days, or until cell death was no long apparent. Transient transfection of siRNA was performed with RNAiMAX, as directed by the manufacturer (Invitrogen, Carlsbad, CA). All siRNA sequences used are listed in Table S2. Expression constructs were transiently transfected in HEK293T cells with LF2000 as directed by the manufacturer (Invitrogen). Tandem-affinity purification and mass spectrometry Minor modifications were made to the purification scheme previously reported to maximize elution during the first and second rounds of affinity purification (1). Protein complexes were eluted from the straptavidin beads with 50 mM biotin in the absence of TEV protease. 0.1% RapiGest (Waters Corp, MA) was included in the final elution from the calmodulin beads. Prior to mass spectrometry, RapiGest was acid cleaved at 37°C for 30 minutes. Affinity pull-downs and Western blotting For streptavidin affinity purification, 2x106 HEK293T cells were lysed in radio- immunoprecipitation buffer (RIPA; 25 mM Tris-HCl at pH 8.0, 150 mM NaCl, 10% glycerol, 1% TritonX-100, 0.25% deoxycholic acid, 2 mM EDTA and protease inhibitor cocktail (Roche, Switzerland), and phosphatase inhibitor cocktail (Calbiochem, San Diego, CA). Cell lysates were cleared by centrifugation and incubated with streptavidin- resin (Amersham, Piscataway, NJ) before washing and eluting in 2XLDS NuPAGE (Invitrogen) loading buffer. Detection of proteins by Western blot was performed using the following antibodies: anti-FLAG M2 monoclonal (Sigma, St Louis, MO), polyclonal anti-VSV (V4888; Sigma), anti-HA polyclonal (1867423; Roche), anti-GFP polyclonal (ab290, abcam), anti-β−catenin polyclonal (9562; Cell Signaling Technology), anti- Active-β-catenin (anti-ABC,clone 8E7; Upstate), anti-βTrCP monoclonal (37-3400; Invitrogen), and anti β-TUBULIN monoclonal (T7816; Sigma).

  • RNA isolation, reverse transcription and quantitative real-time PCR. Total RNA from tissue culture cells or zebrafish embryos were harvested in Trizol (Invitrogen) reagent according to manufacturer’s instructions. RNA quality and quantities were monitored by denaturing gel electrophoresis and UV spectrophotometry, respectively. Singled stranded cDNA was synthesized from 1 µg total RNA using superscript III (Invitrogen) and a 1:1 mixture of random hexamers and oligo-dT. Real- time PCR was performed using the Roche Light Cycler II instrument and software (Roche Diagnostics). PCR was performed in duplicate with the LightCycler FastStart DNA SyBr Green kit (Roche). The PCR conditions are as follows: 35 cycles of amplification with 1 second denaturation at 95°C, and 5 second annealing at 58 °C. A template-free negative control was included in each experiment. Quantitative light cycler PCR primers used were as follows: human WTX (GAC CCA AAA GGA TGA AGC T; and reverse CCC CTC CAA AGA AAC TAG GC), β-catenin gene (TGG ATA CCT CCC AAG TCC TG; and reverse CAG GGA ACA TAG CAG CTC GT), GAPDH (TGA AGG TCG GAG TCA ACG GA; and reverse CCA TTG ATG ACA AGC TTC CCG), zebrafish wtx (TGT GAC GGA CAA GAT GGA AA; and reverse TTT TCA CAG AAG GGG GTG AC), dGFP (TAT ATC ATG GCC GAC AAG CA; and reverse GAA CTC AGC AGG ACC ATG T), zebrafish 18S (CGC TAT TGG AGC TGG AAT TAC C; and reverse GAA ACG GCT ACC ACA TCC AA). Xenopus and zebrafish experiments Xenopus egg extracts were prepared as previously described (2). In vitro transcription and translation of 35S-labeled β-catenin was performed using the coupled transcription- translation T7 system (Promega). For sense RNA injections in Xenopus and zebrafish, mRNA was synthesized using the mMessage machine kit (Ambion). For zebrafish loss- of-function studies, 2.0 ng of morpholino was co-injected with mRNA at the one-cell stage (GeneTools, Inc., Philomath, OR). The MO sequences are WTX-MO1 (5’-ACA GGT GAC TGT GGC CTA ATG GAG CA) and WTX-MO2 (5’-CAT GTT CTA CCT GTA AAA GAA ATA G). In situ hybridizations using digoxigenin-labelled zWTX probes were performed using standard methods. For in situ probe synthesis, the 5’ end of the zebrafish wtx mRNA coding sequence was cloned from zebrafish cDNA using the following primers: forward, 5’-AAA ATA CGG AAG ACA GCT TTC AAA T; reverse, 5’-GAT ATG TGA CAA AAC ATG AGC TAC G. In vitro binding experiments Human GST-VSV-WTX was purified from Escherichia coli and mixed with previously purified CULLIN 1, βTrCP1, or β-catenin in buffered 150mM NaCl. Following 30 minute 4°C incubation, complexes were washed with 5 bed-volumes of 350mM buffered NaCl before elution and Western blot analysis.

  • Supporting Text Generation of WTX stable HEK293T cells It is presumably due to the low level of protein expression in our stable lines that we were successful in generating the WTX line, as we and others observe rapid apoptosis following transient over-expression of WTX in several cell lines(3). Enhanced association between WTX and β-catenin following addition of WNT3A-CM WNT3a stimulation increased the relative amount of β-catenin purifying with WTX (Fig. 2C). We believe the increased β-catenin signal reflects increased levels of WNT3a- induced cytosolic β-catenin as treatment of cells with the proteosome inhibitor MG132 similarly increased the relative amount of β-catenin bound to WTX (fig. S1B). β-Catenin binds the C terminus of WTX The absence of association between WTX-N and β-catenin was not due to altered subcellular localization, as pGlue-WTX and pGlue-WTX-N both localize to the plasma membrane and less strongly to the cytoplasm (fig S2). Interestingly, WTX-C localized to nuclear punctuate structures. WTX enhances β-catenin ubiquitination in Xenopus egg extracts The addition of methylated ubiquitin (MeUb) to the extracts, which terminates poly- ubiquitin chain growth and consequently inhibits proteosomal degradation, allowed us to quantitatively assess the effect of WTX on β-catenin ubiquitination (Fig. 3A,B). siRNA-mediated silencing of WTX sensitizes human cells to WNT3a stimulation Additional controls showed that, as expected, siRNA-mediated silencing of the negative regulators AXIN1/2 and βTrCP1/2 increased WNT3a-mediated β-catenin transcriptional activity (Fig. 3D,E). We validated the extent of siRNA-mediated silencing of WTX by measuring the levels of wtx mRNA and HA-WTX protein in cells following siRNA transfection (fig. S4). WTX inhibits Wnt8-induced axis duplication in Xenopus embryos The experiments in Xenopus cell free extracts and in mammalian cells establish that WTX is an important negative regulator of WNT/β-catenin signal transduction. To extend these experiments to organisms, we first performed gain-of-function experiments in Xenopus embryos, where WNT/β-catenin activity is critical for establishing the embryonic axes(4). Ectopic activation of WNT/β-catenin signaling by injection of Xenopus Wnt8 mRNA in ventral blastomeres induces duplication of the embryonic axis, yielding two-headed tadpoles (fig. S5). When negative regulators of WNT signaling are co-injected with Wnt8 mRNA this blocks the WNT-mediated axis duplication. In the present study, injection of WTX mRNA effectively blocked Xenopus Wnt8-induced axis duplication, thereby supporting its activity as an antagonist of β-catenin (fig. S5).

  • WTX silencing activates Wnt/β-catenin signaling in zebrafish To investigate the function(s) of endogenous zebrafish wtx as a modulator of WNT signaling, we first cloned the zebrafish wtx homologue and performed in situ hybridizations that demonstrated a broad pattern of expression (fig. S6). We next designed two morpholino antisense oligonucleotides (MO), one targeted to the translational start codon of wtx (MO-1) and a second targeted against an internal splice site (MO-2). In zebrafish embryos, it is well-established that ectopic injection of wnt8 mRNA leads to anterior truncations(5). Phenocopying this effect of wnt8 mRNA