Notes: The authors examined the role of p53 in modulating dUTPase promoter activity. Base substitution mutations of Sp1- and E2F-binding sites in the dUTPase promoter were performed using the GeneEditor™ in vitro Site-Directed Mutagenesis System. Each mutant was confirmed by DNA sequencing. To determine growth inhibition, HCT116 human colon cancer cells were seeded in 96-well plates at 3 × 10³ cells/well and treated with 5-fluorouracil (5-FU), fluorodeoxyuridine (FUdR), oxaliplatin or in combination. After 72 hours, the CellTiter^® 96 AQ_ueous One Solution was dispensed into each well and absorbance measured. RNA was isolated from HCT116 p53+/+ and HCT116 p53-/- cells. cDNA was reverse transcribed from 200ng total RNA followed by multiplex qPCR using the Plexor™ qPCR System to amplify dUTPase, thymidylate synthase and GAPDH, a housekeeping gene. The 1.2 kb region of the dUTPase promoter upstream of the transcriptional start site was amplified by PCR and the fragment cloned into the pGL3-Basic Vector. Truncated promoters were also generated by PCR and cloned into the same vector. Drosophila SL-2 cells and HCT116 cell lines were seeded in a 24-well plate and transfected with dUTPase pGL3 promoter constructs or with pCI-Neo:p53WT, pCI-Neo:p53MUT and the empty pCI-neo Mammalian Expression Vector; all transfections included the pRL-TK Vector at a ratio of 1:10. After six hours, the cells were incubated in either fresh medium or medium containing a cytotoxic agent at the appropriate concentration. Thirty hours later, the cells were lysed, quantitated by Western blotting and 20µl of lysate analyzed with the Dual-Luciferase^® Reporter Assay System. Electrophoretic mobility shift analyses (EMSA) were performed using –64 to –91 of the dUTPase-nuclear isoform transcriptional start site in the Gel Shift Assay System. (4031)

Notes: The authors were wanted to study the upstream open reading frame 2 (uORF2) of the 5’ leader of bZIP11 mRNA, which has a role in sucrose regulation. The whole 5’ leader fragment of bZIP11 was subcloned into the pALTER^® Vector and amino acid substitutions were introduced using the Altered Sites^® II in vitro Mutagenesis System. The pGEM^®-T Easy Vector was used to clone two PCR fragments that were then subcloned using restriction enzymes to create a fusion of uORF2 to a different 5’ leader. Arabidopsis seedlings were transformed via particle bombardment. 20mg of plant tissue was ground in Passive Lysis Buffer, centrifuged, and 20µl of the supernatant was assessed for reporter gene expression using the Dual-Luciferase^® Reporter Assay System. (4023)

Notes: Regulation of genes targeted by the ligand-activated aryl hydrocarbon receptor (AhR) has been shown to be controlled by calcium (Ca(2+)) changes induced by AhR agonists such as the environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). This study investigated this link. As part of the study, MCF-7 cells were transfected with various pGL3 firefly luciferase reporter constructs and the control pRL-TK Vector expressing Renilla luciferase. Transfection conditions were as follows: MCF-7 cells were cultured in 24-well plates and transfection was performed using FuGENE® 6 transfection reagentwith a FuGENE:DNA ration of 3:1. Firefly and Renilla luciferase activities were measured using the Dual-Luciferase® Reporter Assay System. (4362)

Notes: In this paper, researchers were looking for efficient chromophores for singlet oxygen generation used for chromophore-assisted light inactivation (CALI) of proteins. The HaloTag^® protein and firefly luciferase were used to test how well the chromophores performed in crude extracts and living cells. The expression vector for an epitope-tagged Luciferase-HTP protein, 3X Flag-Luc-HTP-Myc, was constructed using firefly luciferase amplified from the pGL3-Basic Vector and HaloTag^® (HTP) amplified from the pHT2 Vector. The fusion protein was tested for labeling with a HaloTag^® biotin ligand by transfecting HeLa cells with 8μg of 3X Flag-Luc-HTP-Myc plasmid and 80ng of pRL-SV40 Vector. After transfection, cells were lysed with Passive Lysis Buffer and 2μl of HeLa cell lysate was diluted in 48μl of PBS + BSA and incubated for 30 minutes at room temperature with increasing concentrations of a biotin-HT ligand. The samples then were incubated with streptavidin-agarose for 30 minutes at room temperature, centrifuged and the luciferase activity of 20μl of supernatant was measured using the Dual-Luciferase^® Reporter Assay System. The fusion protein was also tested using two chromophore ligands, ruthenium(II)tris-bipyridyl (Ru-HaloTag^®[HT]) and fluoroscein-HT at a concentration of 100nM, and both were successful as measured by the Dual-Luciferase^® Reporter Assay System. An in vivo CALI was performed by transfecting HeLa cells with 100ng of 3X Flag-HTP-Luc-Myc plasmid and 1ng of pRL-SV40 Vector for 15 hours, and treating the cells with Ru-HT or F-HT for 3 hours. The cells were then irradiated for 30 minutes, placed in the dark for 30 minutes, then the cells were lysed and analyzed with the DLR Assay. (3954)

Notes: The CheckMate™ Mammalian Two-Hybrid System was used to explore the dimerization of epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases without ligand. The intracellular domains of EGFR, ErbB2, ErbB3 and ErbB4 were amplified and cloned into both the pACT and pBIND Vectors. Transfection into NIH3T3 cells in 12-well plates occurred with 0.3 μg of pG5luc Vector (the reporter vector), 0.2 μg of pACT Vector or an equimolar amount of pACT construct, and 0.1 μg of pBIND Vector or an equimolar amount of pBIND construct. After 24 hours, the cells were lysed and luciferase activity assessed using the Dual-Luciferase® Reporter Assay System. (3993)

Notes: The authors identified the N-terminal Src homology 3 (SH3) domain-binding motif of Crk and CrkL as the preferred binding partner of nonstructural protein 1 (NS1), an important virulence factor of the influenza A virus. Interaction of NS1 with Crk, CrkL and other SH3 domain-containing proteins p85, p85β and Eps8L1 was investigated by protein pull-down assays. Expression constructs for biotinylated Crk, CrkL, p85, p85β and Eps8L1 were created by amplifying the 123 amino acid biotin acceptor domain from Propionibacterium shermanii from the PinPoint Xa-T Vector and inserting it upstream of the protein-coding sequences in a pGEX vector derivative. These constructs and a construct encoding Myc-tagged NS1 were transfecting into 293FT cells, and the biotinylated proteins were immobilized from the cell lysate using TetraLink™ Tetrameric Avidin Resin. Any Myc-NS1 that bound to the immobilized protein was detected using Western Blot analysis and an anti-Myc antibody. The authors also investigated the ability of wildtype NS1 or NS1 mutants to inhibit interferon-induced gene expression. A reporter plasmid was created by cloning an interferon-stimulated response element upstream of a minimal thymidine kinase promoter driving firefly luciferase expression. A vector containing Renilla luciferase was used as a control to normalize transfection efficiency. Huh-7 cells were cotransfected with the firefly and Renilla luciferase reporter constructs (0.2µg and 5ng, respectively), treated with interferon-β and lysed using the Passive Lysis Buffer. Firefly and Renilla luciferase activities were measured using the Dual Luciferase Reporter Assay System. (3803)

Notes: The authors of this paper investigated the role of Sox2 in neuronal differentiation. Neurospheres were derived from the brains of normal and Sox2 hyphomorphic mice and used to generate differentiated neural cells. In astroglia from cultures containing a Sox2-GFP-expressing lentivirus, ectopic expression of Sox2 correlated with reduced GFAP expression. The authors investigated the role of Sox2 by amplifying binding sites upstream of the GFAP promoter and cloning them upstream of the thymidine kinase promoter in the pRL-TK vector. The Dual-Luciferase Assay System was used to analyze the effect of Sox2 expression on the luciferase reporter gene. The DeadEnd™ Fluorometric TUNEL System was also used to assess apoptosis in some of the neurosphere-derived cultures. (3953)

Notes: The ORFs of Japanese eel follicle-stimulating hormone receptor (Fshr) and luteinizing hormone receptor (Lhr) were ligated into the pSI Mammalian Expression Vector. Fifty nanograms of this construct or the pSI Vector was cotransfected with 0.5ng of pRL-null Vector and 1µg or a cAMP-responsive firefly luciferase reporter vector into COS cells seeded in 60mm dishes. The next day, the cells were trypsinized, replated into 96-well plates and allowed to recover for 1 day. The transfected cells were serum-starved then treated with hormones six hours before being lysed and enzymatic activity measured with the Dual-Luciferase® Reporter Assay System. (3988)

Notes: The accumulation of the toxic form of the Amyloid-β peptide is known to induce oxidative damage in the brain. Although treatment with antioxidants has not proven effective at controlling AD symptoms, inducing the natural systems in the brain that protect from oxidative damage may provide a possible therapeutic approach. A host of antioxidant and detoxifying enzymes are upregulated by binding of the Nrf2 transcription factor to the ARE (antioxidant response element) regulatory sequence. The authors used a Dual Luciferase^® Reporter Assay to assess modulation of gene activity through ARE by kavalactones. Kavalactones are compounds found in the roots and rhizomes of Kava (Piper methysticum), a plant cultivated an used in some Pacific societies for medicinal and social uses. The ARE1 region from the rat NAD(P)H:quinone oxidoreductase-1 gene was placed upstream of a pGL3 firefly luciferase reporter construct and cotransfected along with a pRL-TK Renilla control construct into PC12 or C6 cells. The data show induction of luciferase activity by kavalactones. Further investigation shows that the kavalactones promote Nrf2 stabilization possibly through the ERK1/2 pathway. (3859)

Notes: To identify microRNA targets, the authors created a Drosha-knockdown cell line and confirmed depletion of Drosha and three randomly selected miRNAs in these cells by quantitative RT-PCR, using β-actin as a control. The reverse transcription step was performed using the ImProm-II™ Reverse Transcription System. The authors then performed microarray analysis to monitor expression of transcripts to determine which were upregulated as a result of Drosha depletion; cRNA used in these microarray experiments was synthesized using the T7 RiboMAX™ Express Large Scale RNA Production System. Cyclin D1 was identified as a potential miRNA target. To screen miRNAs that regulate cyclin D1, the authors cloned the cyclin D1 3´ untranslated region downstream of the firefly luciferase gene of the pGL3-Control Vector and measured luciferase levels in transfected cells using the Dual Luciferase Reporter Assay System. Renilla luciferase in the pRL-TK Vector was used as a normalization control. (3894)

Notes: This article examines the interaction between CAR, a member of the nuclear steroid/thyroid hormone receptor family, which translocates from the cytoplasm to the nucleus when cells are exposed to phenobaritol, and the membrane-associated subunit of protein phosphatase 1 (PPP1R16A, or abbreviated as R16A), which is a novel CAR-binding protein. The R16A protein, it was expressed using the TnT^® Coupled Reticulocyte Lysate System and labeled with ³⁵S. This protein was incubated with GST-hCAR-fusion protein attached to a glutathione resin; the resin was washed, and the bound protein was separated by PAGE and detected by autoradiography. Affinity-tagged R16A was expressed in HepG2 cells, purified and separated by SDS-PAGE. The two major bands were excised, digested with Sequencing Grade Modified Trypsin, lyophilized, resuspended in acetonitrile and subjected to mass spectrometric analyses. The CheckMate™ Mammalian Two-Hybrid System was used to examine the interaction between wildtype and mutated R16A. Forty-eight hours posttransfection into HepG2 cells or 16 hours after DNA injection into mice and liver homogenization, the luciferase activities were measured using the Dual-Luciferase^® Reporter Assay System. (3752)

Notes: Snail is a transcriptional repressor of E-cadherin that enhances both cell attachment and cell detachment in Madin Darby canine kidney (MDCK) and A4231 cells. To investigate this effect, the authors used Western blot analysis and RT-PCR to monitor protein and mRNA levels of the major adhesive proteins expressed in epithelial cells: laminin, heparin sulfate proteoglycan and collagens. For RT-PCR, total RNA was isolated from transiently transfected snail-expressing MDCK and A431 cells and untransfected cells, then reverse transcribed. The resulting cDNA was amplified by PCR using GoTaq^® DNA Polymerase; glyceraldehyde-3-phosphate dehydrogenase was amplified as an internal control. The ability of Snail to regulate the integrin αV promoter was also examined by cloning the promoter and several promoter deletions upstream of a firefly luciferase reporter gene in the pGL3-Basic Vector. Each of these constructs (1µg) and 20ng of pRL-CMV Vector were transfected into MDCK and MDCK/snail cells, and luminescence was measured using the Dual Luciferase Assay System. (3882)

Notes: These authors showed that the ETS transcription factor Erg interacts with the VE-cadherin promoter region and regulates endothelial apoptosis through this interaction. They demonstrated that inhibition of Erg by siRNA resulted in decreased VE-cadherin mRNA and protein levels, and showed that Erg interacts with the VE-cadherin promoter using a CHIP assay. To show the functional relevance of this interaction, HeLa cells were transfected with a pGL4 Vector containing the VE-cadherin promoter region and an expression vector containing Erg2 cDNA. In this reporter assay, Erg overexpression resulted in ~1.8 fold transactivation of VE-cadherin promoter activity, as measured using the Dual-Luciferase® Reporter Assay System. Inhibition of Erg in human umbilical vein endothelial cells also resulted in a loss of viability and an increase in activation of caspase 3 and caspase 7. The authors showed that apoptosis could be significantly decreased by overexpression of VE-cadherin, indicating that Erg regulates survival partially via its interaction with VE-cadherin. The Caspase-Glo® 3/7 Assay was used to measure caspase activity in these experiments. (3872)

Notes: In this paper, the authors hypothesized that bisphosphonates, which are used to prevent tumor metastasis, affect expression of urokinasetype plasminogen activator (uPA), which seems to be critical for prostate cancer metastasis. The authors examined the effect of several bisphosphonates on uPA expression in PC-3 cells. Pamidronate treatment resulted in lower uPA mRNA levels. To investigate the cause, the authors created a uPA reporter construct (pGL3-uPA) by cloning the 5′-flanking region of the human uPA gene upstream of a firefly luciferase reporter gene in the pGL3-Basic Vector. PC-3 cells were seeded at a density of 3 × 10⁴ cells/well in 24-well culture plates and transfected with 0.5µg of pGL3-uPA and 1ng of the Renilla luciferase phRL-TK Vector using FuGENE® 6 Transfection Reagent. At 48 hours post-transfection, the authors measured reporter activity using the Dual-Luciferase® Reporter Assay System to learn that treatment with 100µM pamidronate inhibited transcription of the uPA gene. (4384)

Notes: STAT1 is a transcription factor that is involved in a variety of cellular processes and behaves like a tumor suppressor in many ways. It is associated with apoptosis, inhibition of cyclin-dependent kinases, and it may mediate the antitumor effects of IFN-γ. The authors of this study designed a bioluminescent reporter assay to identify small molecules that enhance STAT1-dependent gene expression. The bioluminescent assay was performed in 384-well plates using both stably and transiently transfected cell lines. The screening assay was robust, producing a Z´factor value of 0.92, and it identified three compounds that specifically enhanced STAT1-dependent transcriptional activity. Firefly luciferase activity in stable cell lines was assessed using the Bright-Glo^® Luciferase Assay System; luciferase activity in the transiently transfected cells was monitored using the Dual-Luciferase^® Assay System. Viability of cells in culture was monitored using the CellTiter-Glo^® Assay. (3732)

Notes: The authors explored the role that nuclear factor (erythroid 2-like) factor 2 (Nrf2) may have in mitigating the cytotoxic effects of bile acids on cells. A reporter vector was constructed using the core sequence of antioxidant reporter element (ARE) sythnesized by annealing two complementary oligonucleotides with Kpn1 and BglII at the 5’ and 3’ ends, respectively, and ligated into the same restriction sites of the pGL3-Promoter Vector (designated pGL3_ARE). To ensure specificity for the experiments, three point mutations were introduced into the ARE sequence (designated pGL3_mARE). To create HepG2 cells that stably expressed human Na(+)-taurocholate co-transporting polypeptide (NTCP), the cDNA clone of NTCP was subcloned into pTargeT™ Mammalian Expression Vector via the NotI site and selected using 500μg/ml G-418. The stable clones or standard HepG2 cells were transiently transfected with 0.1µg of pGL3_ARE or pGL3_mARE, 0.02µg of the control reporter pRL-TK Vector, with or without Nrf2 or dominant negative Nrf2 expression constructs. After overnight transfection, the cells were treated with bile acids for 16–18 hours and luciferase activities determined using the Dual-Luciferase^® Reporter Assay System. Each experiment was done in triplicate and repeated at least two times. (3691)

Notes: The authors of this paper review bioluminescent assay technologies, discussing HTS reporter, cell-based and luciferase biosensor assays. They divide luminescent assays into three basic categories: assays that measure ATP concentration (cell viability and kinase assays), assays that measure changes in luciferase levels (reporter assays, GPCR assays), and assays that measure changes in luciferin levels (protease [including caspase], P450 and MAO assays). (3737)

Notes: The authors tested their hypothesis that Na⁺-H⁺ exchangers (NHE) are involved in the formation of multicullar dome structures in confluent Madin-Darby canine kidney (MDCK) cells and that the Stat3 pathway is involved in regulation of NHEs. The authors performed semi-quantitative RT-PCR to monitor NHE3 mRNA levels in MDCK cells expressing a constitutive Stat3 mutant or a dominant-negative Stat3 mutant. The reverse transcription step was performed using Promega M-MLV Reverse Transcriptase. RAlso, Stat3 activities in low-density cultures and high-density cultures were compared using a reporter gene assay. Four copies of the Stat3-binding site were cloned upstream of a firefly luciferase reporter gene, and the resulting vector, along with the pRL-TK Vector for normalization, were transfected into MDCK cells. Luciferase activities were measured using the Dual-Luciferase Reporter Assay System. (3910)

Notes: The authors examined transcriptional regulation of the vitamin D receptor (VDR) by p53 and p63, a member of the p53 family, under stressed and unstressed conditions. Reporter constructs with the full-length and minimal VDR promoters controlling expression of firefly luciferase were cotransfected with p53 or p63 expression constructs, and transcriptional activation of the VDR promoter was monitored using the Dual-Luciferase^® Reporter 100 Assay System. Results were normalized to Renilla luciferase activity. Interaction between p73, another member of the p53 family, and the VDR promoter was examined using chromatin immunoprecipitation. The imunnopreciptated chromatin was reverse crosslinked, DNA was eluted and VDR and p21 sequences were detected by PCR using GoTaq^® Green Master Mix. (3715)

Notes: While the absence of the Vitamin D receptor (VDR) has profound effects in skin cells, mutation of 25-hydroxyvitamin D 1α-hydroxylase (24OHase), the enzyme required for 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) hormone biosynthesis, has little effect on the skin. To determine how VDR may transactivate independent of the 1,25(OH)₂D₃ ligand, the human 24-hydroxylase promoter was amplified from MCF-7 genomic DNA, digested with XhoI and HindIII and inserted into the pGL3-Basic Vector. Mutations in the proximal and distal vitamin D response elements in the human 24-hydroxylase promoter were introduced using the GeneEditor™ Site-Directed Mutagenesis System. HaCaT cells, primary human fibroblasts or primary human keratinocytes were seeded at a density of 3.2 × 10⁴ cells/well in 12-well plates and transiently transfected with reporter constructs. After 18 hours, the cells were exposed to 1,25(OH)₂D₃, 9-cis-retinoic acid, ethanol vehicle, or no additive and harvested 24 hours later. The luciferase activity of the cell lysates was measured using the Dual-Luciferase^® Reporter Assay System. Five micrograms of RNA purified from mouse keratinocyte and fibroblast cultures was reverse transcribed and amplified for the 24OHase transcripts using the PCR Master Mix. The products were analyzed on ethidium bromide-stained 2% agarose gels. (3695)

Notes: The authors used reporter assays and coimmunoprecipitation experiments to compare the zebrafish (Danio rerio) Toll-IL-1R-containing adaptor molecule 1 (TICAM1) activation of NF-κB and zebrafish type I IFN to mammalian TICAM1 activation. 293H and ZFL (zebrafish liver) cells were cotransfected with 400 ng of TICAM1 construct (mouse, zebrafish or a deletion construct), 400 ng of a reporter construct (e.g., a zebrafish IFN promoter cloned into the pGL3-Basic Vector) and 10 ng of pRL-CMV Vector, an internal control to normalize data. After 24 hours for 293H cells and 48 hours for ZFL cells, the transfected cells were lysed, and luciferase activity was measured using the Dual-Luciferase^® Reporter Assay System. For coimmunoprecipitation experiments, 293H cells were cotransfected with a total of 8µg of plasmids (3µg of zebrafish or mouse TICAM1 construct, 3µg of interacting protein construct, 1µg of the pAdVAntage™ Vector, and 1µg of antiapoptotic protein p35 construct). Forty-eight hours posttransfection, the cells were lysed, the protein bound to affinity resins and analyzed by Western blot. (3755)

Notes: In this study, the HIV Tat gene was expressed in tomato plants. Mice were given 10mg of tomato fruit extract from either transgenic or wild-type plants orally, intraperitoneally and intramuscularly. A strong anti-Tat immune response was obtained in mice immunized with the transgenic fruit, regardless of the administration route. Mice that received oral vaccination developed early evidence of mucosal immunity. Sera from the immunized mice inhibited Tat-dependent transactivation of the HIV long terminal repeat promoter in a luciferase reporter assay. (3706)

Notes: The authors characterized a juvenile hormone response element in Drosophila melanogaster (DmJHRE1) and identified two proteins that bound to a DmJHRE1 affinity column. Proteins eluted from the column were digested with Sequencing Grade Modified Trypsin, subjected to liquid chromatography-tandem mass spectrometry and identified as FKBP39 and Chd64. DmJHRE1 transcription regulatory activity was confirmed using reporter constructs with DmJHRE1 sequences regulating expression of firefly luciferase in Drosophila L57 and S2 cells. A vector with Renilla luciferase and the Autographa californica multicapsid nucleopolyhedrovirus IE1 promoter was used for normalization. Luciferase activities were measured using the Dual-Luciferase^® Reporter Assay System. Potential interactions between FKBP39, Chd64 and several candidates proteins for the JH receptor were examined using the MagneGST™ Pull-Down System. Each bait protein was expressed as a GST-fusion protein in E. coli and immobilized using MagneGST™ Glutathione Particles. [³⁵S]Methionine-labeled prey proteins were expressed using the TNT^® T7 Quick Coupled Transcription/Translation System. (3784)

Notes: The authors of this paper describe the generation of induced pluripotent stem (iPS) cells from human dermal fibroblasts. STR analysis using the PowerPlex^® 16 System showed that patterns of 16 STRs in the clones matched the parent cell line. Luciferase assays to assess activity of the OCT3/4 and Rex1 promoters were performed using the Dual-Luciferase^® Assay System. (3951)

Notes: To explore the interaction of liver receptor homolog (LRH)-1, a known suppressor of sterol regulatory element-binding protein (SREBP) transcriptional activity, human LRH-1 was reverse transcribed then amplified by PCR from total RNA from HepG2 cells. The amplification product was ligated into the pTargeT™ Mammalian Expression Vector to create pTarget-LRH1. For reporter experiments, a PCR fragment that encompassed the 1.3kb 5’-promoter region of the human small heterodimer partner (SHP) gene was cloned into the pGL3-Basic Vector (designated pSRB). The pGL3-Promoter Vector was used to construct pLRHREx3, which contains three LRH-1 response elements, and the insert was generated using synthetic oligonucleotides. HEK293 cells were cotransfected with 0.2µg of a promoter-firefly luciferase construct, 0.1µg of a SREBP expression plasmid, 10ng of phRL-TK Vector and 0.2 or 0.6µg of pTarget-LRH1. Alternatively, the cotransfected plasmids were 0.2µg of pSHP, 0.1µg of pTarget-LRH1, 10ng of phRL-TK Vector and 0.2 or 0.6µg of a SREBP expression plasmid. The pLRHREx3 construct (0.2µg) was cotransfected with 0.1µg of a LRH-1 expression plasmid, 0.2µg of pCMXPGC-1α (peroxisome proliferator activated receptor γ coactivator-1α), 10ng of phRL-TK Vector, and 0.1 or 0.3µg of a pSREBP expression vector in HEK 293 cells. Luciferase expression was assayed 48 hours post-transfection using the Dual-Luciferase^® Assay Reporter System. To express SREBPs and LRH-1 in vitro, inserts were ligated into the pTNT™ Vector, synthesized using the TNT^® Coupled Transcription/Translation System with radiolabeled methionine. Ten microliters of the ³⁵S-labelled protein was then used in a GST-pulldown assay. (3692)