Objective:Toinvestigatethepost-transcriptionalregulationofp21WAF1/CIP1byp53.Methods:TheMDA-MB-468cellshaveendogenousmutantp53andtheMCF7cellslineshavewtp53.Recombinantp53expressionandp21WAF1/CIP1inductionweredetectedbyWesternblotanalysis.Northernblotanalysiswascarriedouttoexaminewhetherchangesinp21WAF1/CIP1proteinlevelsinMCF7cellstreatedwithAdCMVp53arereflectedatthemRNAlevel.FlowcytometricanalysisofMCF7cellsfollowingoverexpressionofrecombination.Results:Theratioofp53:p21WAF1/CIP1wasbelow1attheearlystagesofAdCMVp53infection,butincreasedto1.6byday3andto9.7byday5post-infection.Asexpected,p21WAF1/CIP1expressionwasnotdetectableinMDA-MB-468cellsdespitethepresenceofhighlevelsofmutantp53protein.TheG1/SratiosinuntreatedcontrolsandAdCMVβgalinfectedMCF7cellswere1.10and1.35,respectively.ByNorthernblotanalyzingthep21WAF1/CIP1:GAPDHratiosatdifferenttimepointsagainsttheratioattimepoint0,amaximum3-foldinductionofp21WAF1/CIP1mRNAexpressionrelativetountreatedcontrolwasobservedonday1post-infection.TheflowcytometricanalysisindicatedthatMCF7cellsinfectedwithAdCMVp53undergoG1arrestatbothtimepointsstudied,withG1/Sratiosrangingfrom5.54atday1to5.65atday7.TheG1/SratiosinuntreatedcontrolsandAdCMVβgalinfectedMCF7cellswere1.10and1.35,respectively.Conclusion:Thisstudydemonstratedthatp53couldregulatep21WAF1/CIP1geneexpressionatboththetranscriptionalandpost-transcriptionallevelsinMCF7cells.Thelattermechanismmaybeinvolvedinorberesponsiblefor,theinductionofcellcyclearrestbytranscription-defectivemutantsofp53.
