案例生物化学二repair class zhanglan

GeneticInformationContentsofThis•TypeofDNA•DNARepair• •SomethingneedsDNADNAofmutation

DNAIsConstantlyChangingthroughtheProcessofMutationlevel NaturalpolymeraseEndogenousDNAROS,ExogenousDNARadiation,Chemical 中的错碱基配对的错误频率约为10-4-10-聚合酶本身具有校对作用：将不正确插入的核苷酸切除掉，重新加上正确的核苷酸。这样，每掺入一个核苷酸，发生错误的机会有。EndogenousDNA腺嘌呤的稀有互变异体腺嘌呤的稀有互变异体与胞嘧胸腺嘧啶的稀有互变异构体与鸟嘌异异构体间自发地相互变化形成导致下一世代中G－C配对取代A－T配•碱基的环外氨基有时会自发脱落，从而胞嘧啶会变成尿嘧•胞嘧啶自发脱氨基的频率约为每个细胞每天190•碱基的环外氨基有时会自发脱落，从而胞嘧啶会变成尿嘧•胞嘧啶自发脱氨基的频率约为每个细胞每天190OO Nitrous DeaminationofcytosinetoMutationGenerationpassedontodaughterDNAs deletionpassedontodaughter碱基修每个哺乳类细胞每天DNA单链断裂发生的频率约为5万次ChemicalTypesChemicalTypesofX-raysandX-raysandγ-raysstrandbreaks;base/sugardestructionUVlightUVlightpyrimidineg紫外线引起的DNA损(cyclobutanering)连成二聚体。260nm Disruptssynthesis;goodforsterilizationofbacteria,badforskinTypesofPhysicalChemical ogs:AlkylatingIntercalatingIntercalating DNAcanIncorporate5-BU ceofNote:changesaG-CpairintoanA-Tpair(G>Aisatransition,C>Tisatransition) EthylmethaneSulfonate(EMS)AlkylatesIntercalatingInsertionsorTheadditionorlossofoneormorebasesinaDNAFrameshiftTheORFofaproteinencodedgeneischangedsothattheC-terminalsideofthemutationiscomple ychanged.ThetranscriptsisdegradedviaNonsense-mediateddecay(NMD)pathwaysifitcontainsprematuretermination(stop)codons(PTCs)EffectsofPoint3rdpositionofa Silent CodingDNAalteredCodingDNAalteredCodingDNAstopCodingDNAstoptruncated

DNAreplication-independentproductionoferroneousTumorTwoStrikeselectivegrowthselectivegrowth

Smallchange,greatsecondroundsecondroundofclonalgrowththatallowsanexpansionofcellnumberOtherdrivergenemutation gene Mut-Drivercodinggenes74-64-~50%chromatin(modification)factors:HIST1H3B,H3F3A,DNMT1,TET1…...Epi-DriverGeneticHeterogeneityofl

Thejoiningofafragmentedchromosometoanon-homologouschromosomethebreakageofachromosomeinwhich eslostduringcell

ExtracopiesofgenesaregeneratedonathebrokenchromosomesegmentisreversedandinsertedbackintothechromosomeIsochromosomescontaineithertwoshortarmsortwolongarms,derivedfromimproperdivisionofthecentromere.ChromosomeNumberAneuploidyAneuploidy:Turnermassive,complexchromosomeNatureMedicine18,1630–1638Genome-widedistributionofsomaticDNACell.2012.148(1-2):DNADNARepairCellularCellularprotectionfromDNANaturalerrors:polymerasebaseselection,proofreading,mismatchrepairEndogenous/exogenousDNAdamage:Baseexcisionrepair,Nucleotideexcisionbination(DNAdoublestrandbreak)polymerasebypass(TranslesionDNAsynthesis)ProofreadingofDNAMostDNApolymerasescontain“proofreading”activity(3’to5’exonuclease)increasesfidelityofreplicationby100X.ProkaryoticMutSbindstoDNAatmismatchsiteMutLrecruitedbyMutLactsasmat betweenMutSandMutHMutHcreatesanick5’totheunmethylatedGATCsiteExonucleasedegradessectionofthestrandcontainingRecognizescorrectstrandbecauseitisunmethylatedGapinDNAisPhotoactivationRepairinPREbondbetweenPhotoreactivation(theenzymeDNApotolyasecapturesenergyfromlightDirectDirectTypesTypesoflesionsrepairedbyOxidativelesions;8-oxo-G,highlymutagenic,mispairswithA,producingGC-->TADeoxyuracil(dU):frommisincorporationofdUordeaminationofdC-->dU,Spontaneousdepurination(esp.G)yieldabasicsitesthatarerepairedbysecondhalfofBERRecognitionofunusualthrough“base out”recognizedbyDNAglycosylaseDNAglycosylaseleision-andhumancellshave8DNAglycosylaseswithdifferentBaseExcisionAPIfadamagedbaseisnotremovedbybaseexcisionbeforeDNAreplicationAfail-safeNucleotideExcisionNucleotideExcisionRecognitionofdoublehelixEnzymescleavedamagedDNAoneithersideofthelesionDNApolymeraseandligasefillinthegap.ModelforEukaryoticNucleotideExcisionRepair:XerodermaPigmentosum（XP） 性干皮病NERenzymeincludingXPA,XPC,XPDandXPFisassociatedwithbinationbinationTranslesionDNAsynthesis:CatalyzedbyaspecializedclassofDNApolymerasesthatsynthesizeDNAdirectilyacrossthesiteofthedamageCharacteristicsCharacteristicsoflesionbypassinresponsetoDNAdamageTheactivationofbinationPost-ReplicationRecA:交换DNA链EmergencyDNAEmergencyDNARepairforDoublestrand TheexchangeofhomologousregionsbetweentwoDNADeleteriousmutationswouldn’taccumulateineachbinationgeneratesgeneticdiversity;Criticalforantigenicvariation.Diploideukaryotes:crossingMitoticand binationcanoccurbothduringmitosisandmeiosisOnlymeiotic binationservestheimportantroleofreassortinggenes binationmaybeimportantforrepairofmutationsinoneofapairofsisterchromatidsThecross-strandHollidaystructureisanintermediatein bination(partI)Thecross-strandHollidaystructureisanintermediatein bination(partII) lian RecBCDexonuclease:opensRecBCDRecBCDexonuclease:opens3’Uponrecognitionofχ,the3’to5’nucleaseactivityisattenuated,aweaker5’to3’nucleaseactivityisactivatedontheoppositeTheundegraded3’end

RecA:neededtoformRecA:neededtoformtriple cedstrandbindstooriginalcomplementarystrandoftheinvasivestrandtocreateHollidayHollidayEfficientbranchmigrationrequiresRuvAandEfficientbranchmigrationrequiresRuvAand-resultantstructurebetterabletoundergobranchmigrationandRuvB:formsahexamericringaroundtheDNADNAispumpedthroughtheringusingATPcleavagetodrivethethesynapseis dto RuvC:RuvC:specificallycuttingtheHollidayRuvCisaspecializedresolvethecrossedtheHollidayBreakRepair3’ssDNAGeneGeneTLoxP:34bp:8-bpTLoxP:34bp:8-bpsequenceflankedby13-bpinvertedDeletionofloxP-flankedTissue-SpecificTissuespecific ConditionalKnockoutTissuespecific Silencingthe3rd21#chromosomeusingNature,2013(500):296-clusteredregularlyinterspacedshortpalindromicrepeats(CRISPR)/CRISPR-associated(Cas)systemsNature,2013(495,)GN(20) MovingMcClintock,1983NobelPrizeinMedicineor geneticelementsfoundinIStransposasegeneflankedbyashortinvertedterminalrepeatsTn:transpositionelementsandadditionalshortinvertedterminalrepeatsCutandPasteTranspositionDuplicative like