TopoisomeraseIDrugScreeningKitProductDescription
TheTopoIDrugKitintroducestransientnicksinDNAatspecificsites. DetectionofthesetransientDNAnicksrequirestrappingtheenzymeonDNAinanickedintermediatecomplexusingproteindenaturants.TheresultingcovalentDNA/topoIcomplexescontainnickedopencircularDNAwhichcanbedetectedbyagarosegelelectrophoresis(withethidiumbromide). Trappingnickedintermediatesisrelativelyinefficient;however,inhibitors,suchasthenaturalproductcamptothecin,stABIlizetheintermediateandleadtoanincreaseinthenickedDNAproduct. ThisformsthebasisforamechaNISTicdrugscreeningassaydesignedtoallowdetectionofagentsthataffecttopoisomeraseIbystabilizingthecleavedintermediatecomplex. TheTopoGENTopoIDrugScreeningKitisdesignedtoallowtheinvestigatortoquicklyidentifynovelinhibitorsoftopoIenzyme(soldseparately). ThekitwillallowdetectionofnovelcompoundsthateitherstabilizethenickedintermediateorotherwiseinhibitcatalyticactivityoftopoisomeraseI.
TopoisomeraseIDrugScreeningKitContents(representativefor100assaykitsize):
-SupercoiledpHOT-1DNA,25µg
-RelaxedandnickedplasmidDNAMarkers
-10XTopoisomeraseIassay/cleavagebuffer,300ul
-Sodiumdodecylsulfate(SDS)terminationbuffer(10%)
-10XgelloADIngdye
-Controlinhibitor(Camptothecin;lyophilized)
-ProteinaseK
-Detailedinstructionmanual
Note:TopoisomeraseIenzymesoldseparately.
TheTopoisomeraseIDrugScreeningKitisdesignedtoworkwithhumantopoIavailablefromTopoGEN.Sincecleavageassaysrequiremoreenzymethancatalyticassays,TopoGENsellstheenzymeinlargerlotswhichtakesthisdifferenceintoaccount.
UseoftheTopoisomeraseIDrugKit
Reactionsindicatedaboveeachlanewerecarriedoutusing5unitsofTopoGENtypeItopoisomerase. Thereactionswereincubatedfor30minat37CandstoppedwithSDS. AfterdigestionwithproteinaseK(50ug/ml,60minat37C),sampleswereloadedontoa1%agarosegel. Undertheseconditions,withexcesstopoIandcamptothecin,significantconversionofsupercoiled(formI)DNAtoopencircular(OCDNA)wasobserved. Itisimportanttorecognizethatcleavageassayswillconsumemoreenzymethancatalytic(relaxationtype)assays. Thisisbecauseeachcleavageeventconsumesoneenzymemolecule;i.e.,thereactionrequiresstoichiometicamountsoftopoI.