Beta-galactosidaseReporterGeneAssay(LiquidForm) REFERENCE:Hoffman,G.,Garrison,T.R.,andDohlman,H.G.,AnalysisofRGSproteinsinSaccharomycescerevisiae,MethodsEnzymol.344:617-631,2002. 1.Growastartercultureat30Cshaking(250rpm)untilitreachessaturation. ***ThecellsshouldbetransformedwithayeastexpressionvectorcontainingthelacZgeneunderthecontroloftheFUS1promoter.Alternately,astraincanbeusedwiththeFUS1-lacZreporterintegratedintothegenome.Thesematerialsareavailablefromanumberofyeastlabs,includingourown. 2.Usingthesaturatedstarterculture,inoculate5to25mloftheappropriatemedia. ***Rarely,atransformedcolonywillnotrespondatalltopheromone.Thecauseisnotknown.Toeliminatethese"flatliner"strainspickseveraldifferentcolonies.Twohoursafterre-inoculationtakeanaliquotofeachandperformasmallscaleassay(plusandminus1doseofalpha-factor).Discardanythatfailtochangecoloraftersubstrateaddition. 3.Growat30Cshaking(250rpm)untiltheOD600nm~0.8(thisisusuallydoneovernight). ***Thisisthetrickiestpartoftheassay,sinceitisdifficulttogetdifferentstrainstoreachOD600nm~0.8atthesametime.Thebestwaytohandlethisistostarta2mlstartercultureabout3-4daysbeforetheassay.Thenightbeforetheassay,starta10to25mlintermediateculture.Themorningoftheassay,measuretheabsorbanceofalloftheintermediateculturesanddilutethemdowntoanOD600nmof0.2inpre-warmedmedia.Thestrainswillnowonlyhavetogothroughtwodoublingsandtheamountofvariancebetweenthemshouldbereduced.IfthestrainsstillreachOD600nm~0.8atdifferenttimes,itisacceptabletoputstrainswhichhavereachedOD600nm~0.8onicewhilewaitingfortheothers. ***Re-checktheabsorbanceofallculturesbeforeproceeding. 4.Aliquot10ulofalpha-factorattheappropriateconcentrationsinto96wellplates. ***Eachstrainshouldbetestedwith8to10differentconcentrationsofalpha-factorintriplicate. ***Agoodsetoffinalalpha-factorconcentrationsfortestingansst2deltamutantstrainis:0,0.00003uM,0.0001uM...0.3uM.ForstrainsexpressingamammalianoryeastRGSprotein,thefinalconcentrationsshouldbe100-300foldhigher.Theconcentrationofalpha-factoraddedtoeachwellmustbe10-foldhigherthanthedesiredfinalconcentration. ***Keepafrozenstockofalpha-factorandmakeanewsetofdilutionseachtimetheassayisperformed,sincealpha-factorissubjecttodegradationuponrepeatedfreeze-thawcyclesorexposuretoroomtemperature. ***Amulti-channelpipettorandaplasticpipettorbasin(FisherScientific,#13681100)ishelpfulforaliquotingsolutions. 5.Add90ulofcellstoeachwell. 6.Incubate90minat30C,shakinggently. 7.Duringtheincubation,preparetheFDGsolution. Solution#1:1mMFDGstockdilutedin25mMPIPES(pH7.2) Solution#2:5%TritonX-100dilutedin250mMPIPES(pH7.2) ***MixSolution#1andSolution#2inequalamountsjustpriortouse,andpourintoacleanpipettorbasin. FDGStock:10mMFDG(Fluoresceindi-b-D-galactopyranoside,Molecularprobes,#F-1179)indimethylsulfoxide(DMSO)(FDGshouldbestoredinDMSOat-20C;itismorestableinsolution.) 8.Afterthe90minincubation,add20ulFDGsolutionperwell.Shakeplatesgentlyandbriefly. 9.Coverinaluminumfoilandincubateat37Cuntilabrightyellowcolorappearsinsomeofthewells. ***Thiscantakefrom10to90min.Donotincubatelongerthan90min. 10.Stopthereactionbyadding20ulof1MNa2CO3perwell.Shaketheplatesgentlyandbriefly. 11.Readtheplateswithafluorescencemulti-wellplatereaderusinganexcitationof485nmandanemissionof530nm. 12.Readtheabsorbanceandnormalizeforcelldensity. ***Alternately,usethefinalabsorbancevalues[obtainedimmediatelybeforealiquotingcellsintothe96wellplate(step3)]tonormalizeforcelldensity. Updated01/23/02