A3SR protein kinasesGUexon 2Aexon 1CAU4/U6CstFsplicing factor SF3BSR-phosphatasesSR-binding sitesCstFSR-kinasesGMPSR-proteins3AGAU25Formation of the active Spliceosomal C complexRngtt (capping enzyme)5splicing factor SF3APoly(A)pb IIU5U2AFexon 2(2b)Kinases Phosphorylating RS domains?Putative Alternative SplicingYYYYAAUAAA5 G capright click on blue text for detailed informationFormation of the Spliceosomal B complexSR-repressor proteins3U1 snRNPATP533Formation of the Spliceosomal E complexSF3b14bMethylation of mRNA5Additional SR proteinsRNA helicasesplicesome associated helicasesSR protein phosphatases3Polr2aLariat Formation and 5'-Splice Site CleavageU2 snRNPsexon 2U2 snRNPexon 2pre-mRNAAdditional Factorsexon 1snRNP Sm core complexCF IUGCF IISpt5Processing of Intron-Containing Pre-mRNAAdditional FactorsCleavage of mRNA at the 3'-endsnRNP Sm core complexAGexon 1Poly(A) polRNA helicase AU6 snRNPYYYYRnmt (methyltransferase)HOMOLOGY MAPPRNAi pathwayCap BindingFormation of pre-mRNPsAlternative Splicingexon 2Regulation ofAGMisc.Poly(A) polymerase alphaFormation of the Spliceosomal B complexNote: New participating members shown at each stepmRNA cappingiPomRNA splicing (major pathway)535U5CPSFAccessory ProteinsRegulatorsYYYYmRNA splice site selection3YYYYU4 snRNPAAG5(2c)5degradedexon 1SR-proteinsexon 2Aexon 1Formation of the Spliceosomal A complex(2a)CFI35(3)AU5 snRNPP-CF IIInternal methylation of mRNAFormation of the Spliceosomal A complexYYYYU2 snRNPPUGPiFormation of the Spliceosomal C complexU1 snRNPU2AFU4:U5:U6 tri-snRNP complexAAAAAAAYYYY3mRNA CappingPrimary RNA transcriptintronU13AGsnRNP Sm core complexFormation of pre-mRNPsheterogeneous nuclear ribonucleoproteins3CPSF5655U6Additional Factors(1)mRNA 3'-end processingSerine/Argenine Rich Proteins(SR)SR-proteinsCleavage at the 3'-Splice-Site and Exon LigationInternal methylation of mRNAAG5hnRNP regulatorshnRNPsexon 1mRNA polyadenylation(2)Poly(A)-binding protein IIU4SR-binding sitesFormation of the Spliceosomal E complexhnrnpdsmx5hnrpabhnrnph1lCLK3srp54ptbp1asfrs10clk2ac20orf14U1 snRNASF3A3DNAJC8SFRS4rbm17u2af1spophnrnpkprpf3U4 snRNAwdr57phf5aNCBP1sf3a2snrpbhnrnpmcdc40prpf18cpsf2ssfa1snrpasf3b4Rnu6hnrnpa3sfrs16clk4addx1ptbp2asnrpb2sugp1ybx1EFTUD2sfrs1snrpflnxf1SNRPBprpf4bbHNRPH2PRPF8SRPK2POLR2Apcbp2RNU2sfpqfussf3a1snrpbdhx16hnrnprhnrpa1HNRPA2B1U5 snRNAdicer1CLK1srrm1snrpgprpf40aHEABzgc:55440smc1alcstf3rbm5cugbp2prpf4snrpd1prpf4ppm1glsm7ddx20mettl3sfrs3sfrs6aRBMXDHX9SFRS14dhx8cd2bp2sfrs5aDHX38ncbp2PRPF8cugbp1sfswapsnrpd2cstf1papolacpsf5prmt1srek1rnps1txnl4aPSKH1prmt2sf3b5cpsf3tmed10supt5hsf3b2sf3b1nonossfa1srsf7asnrpedhx15snrpa1hnrplCSTF2Tsrsf2bsrsf10aRNMTcelf4xrn2ssfa1pabn1srpk1cstf2rnpc2hnrnpccpsf1zgc:77804SNRPD3narhnrpurngttsmx5srsf9snrp70clk2bclk4bptbp2bsrsf10bsrsf10asrsf10bsfrs5bsfrs6b