RNA的剪接解析VIP免费

RNASplicingRNASplicingRNARNA的剪接的剪接Figure13-1Primarytranscript多数真核基因都是断裂的，其编码序列由非编码序列隔开Exons(外显子):thecodingsequencesIntrons(内含子):theinterveningsequencesRNAsplicing:theprocessbywhichintronsareremovedfromthepre-mRNA.Alternativesplicing(可变剪接):somepre-mRNAscanbesplicedinmorethanoneway,generatingalternativemRNAs.60%ofthehumangenesaresplicedinthismanner.Topic1:Topic1:RNARNA剪接的化学反应剪接的化学反应RNA的序列决定剪接位点Thebordersbetweenintronsandexonsaremarkedbyspecificnucleotidesequenceswithinthepre-mRNAs.剪接应该在那里发生？Figure13-2Theconsensussequencesforhuman5’splicesite(5’剪接位点):theexon-intronboundaryatthe5’endoftheintron3’splicesite(3’剪接位点):theexon-intronboundaryatthe3’endoftheintronBranchpointsite(分枝位点):anAclosetothe3’endoftheintron,whichisfollowedbyapolypyrimidinetract(Pytract).两相邻的外显子连接起来，内含子以套马索(Lariat)的结构被除去两次转酯化反应(transesterification):Step1:TheOHoftheconservedAatthebranchsiteattacksthephosphorylgroupoftheconservedGinthe5’splicesite.Asaresult,the5’exonisreleasedandthe5’-endoftheintronformsathree-wayjunctionstructure.ThechemistryofRNAsplicingFigure13-3Three-wayjunction丁字路口结构Three-wayjunctionFigure13-4Step2:TheOHofthe5’exonattacksthephosphorylgroupatthe3’splicesite.Asaconsequence,the5’and3’exonsarejoinedandtheintronisliberatedintheshapeofalariat.Figure13-3来至不同RNA分子的外显子可以通过反式剪接(Trans-splicing)连接起来Trans-splicing:theprocessinwhichtwoexonscarriedondifferentRNAmoleculescanbesplicedtogether.Trans-splicingFigure13-5NotalariatTopic2Topic2：：剪接机器THESPLICESOMEMACHINERYTHESPLICESOMEMACHINERYRNA剪接由一个大的叫剪接体(spliceosome)的复合体执行剪接体由大约150个蛋白和5snRNAs组成剪接体的许多功能都是由其RNA组分执行的5RNAs(U1,U2,U4,U5,andU6,100-300nt)叫核内小RNA(smallnuclearRNAs,snRNAs).snRNA和蛋白的复合体叫核内小分子核糖核蛋白smallnuclearribonucleoproteins(snRNP,发音“snurps”).剪接体是最大的snRNP，在剪接的不同阶段它的组成会有变化1.识别the5’splicesiteandthebranchsite.2.将这两个位点带到一起.3.催化(or帮助催化)RNA断裂.RNA-RNA,RNA-proteinandprotein-proteininteractionsareallimportantduringsplicing.snRNPs在剪接中的角色Figure13-6RNA-RNAinteractionsbetweendifferentsnRNPs,andbetweensnRNPsandpre-mRNATopic3：剪接途径SPLICINGPATHWAYSSPLICINGPATHWAYS剪接体的装配,重排,和催化:thesplicingpathway(Fig.13-8)装配step11.U1recognize5’splicesite.2.OnesubunitofU2AFbindstoPytractandtheothertothe3’splicesite.TheformersubunitsinteractswithBBPandhelpsitbindtothebranchpoint.3.Early(E)complexisformed装配step21.U2bindstothebranchsite,andthenAcomplexisformed.2.Thebase-pairingbetweentheU2andthebranchsiteissuchthatthebranchsiteAisextruded(Figure13-6).ThisAresidueisavailabletoreactwiththe5’splicesite.Figure13-8EcomplexAcomplexFigure13-6b装配step31.U4,U5andU6formthetri-snRNPParticle.2.Withtheentryofthetri-snRNP,theAcomplexisconvertedintotheBcomplex.Figure13-8AcomplexBcomplex装配step4U1leavesthecomplex,andU6replacesitatthe5’splicesite.U4isreleasedfromthecomplex,allowingU6tointeractwithU2(Figure13-6c).ThisarrangementcalledtheCcomplex.Figure13-8Figure13-6cBcomplexCcomplexinwhichthecatalysishasnotoccurredyet催化Step1:FormationoftheCcomplexproducestheactivesite,withU2andU6RNAsbeingbroughttogetherFormationoftheactivesitejuxtaposesthe5’splicesiteofthepre-m...