exportMultipleadaptorproteins(e.g.,Yra1/Aly/REF1andSRproteins)drivemRNP•exportbyloadingdimericexportreceptor(Mex67-Mtr2/TAP-p15/NXF1-NXT1).Inyeast,TREXcomplexrecruitedtopolymerase;DECDhelicaseSub2loads•Yra1ontomRNA.Invertebrates,TREXbindscapviasplicing-dependentinteractionofAly/REF1(vertebrateYra1)withCBP80.ExportcoupledtotranscriptionviaSAGAchromatin-remodelingcomplex,•whichbindsTREX2andrelocatessomegenestonuclearporeforexport.Exportcoupledto3•′endprocessing(TREXrequiredfor3′endformationandreleaseofmRNPfromtranscriptionsite).Differentexportadaptorsorreceptorsconfertranscriptspecificity,e.g.,TREX•isimportantforexportofheat-shockgenetranscripts.TransitthroughporeviabindingofMex67/TAP/NXF1tonucleoporinFG•repeats.mRNPremodeledoncytoplasmicsideofporebyDbp5DEAD-boxhelicase•(whichisactivatedbyGle1andinositolphosphate).capping7-methyl-guanosinecapaddedto5•′endofRNAby3enzymes:RNA5′triphosphatase(RT),guanyltransferase(GT)(bifunctionalRT-GTinvertebrates),andmethyltransferase(MT).Cappingenzymes(RTandMTinyeast,RT/GTinvertebrates)recruitedtoRNAby•Ser5-phosphorylatedRNAPolIICTD.Capaddedwhen~20ntofRNAistranscribed.Capadditioncoupledtopromoter•clearanceandearlytranscriptionelongation.Nuclearcap-bindingproteins(Cbc2-Sto1andCbp80-20)replacedbycytoplasmic•CBPs(Cdc33/eIF4E)afterexport.splicingPre-mRNAsplicing,atwo-steptrans-esterificationreaction•withabranchedintermediate,ismediatedby5snRNAs(insnRNPs)and80–200proteins.U1snRNP,BBP/SF1,andMud2/U2AFrecognizeRNAelementstoformacommitmentcomplex.U2snRNPjoinsnext,followedbyU5,U4/U6snRNPs.Aftermajorrearrangements,catalyticallyactivespliceosomecontainsU2,U5,andU6.8DExH/D-boxhelicases(Prp5/DDX23,Sub2/UAP56,•Prp28/DDX46,Brr2/U5-200KD,Prp2/DHX16,Prp16/DHX38,Prp22/DHX8,Prp43/DHX15)andaGTPase(Snu114/SNRP116)facilitaterearrangementsandregulatereactionfidelity.Vertebrateexon-exonjunctionsmarkedbyEJC,which•triggersNMDwhendownstreamofastopcodon.SplicingcoupledtomRNPexportviaproteinsthatactin•bothprocesses,suchasSub2/UAP56,serine-a...
