Function:Subunit of the splicing factor SF3B required for 'A' complex assembly formed by the stable binding of U2 snRNP to the branchpoint sequence (BPS) in pre-mRNA. Sequence independent binding of SF3A/SF3B complex upstream of the branch site is essential , it may anchor U2 snRNP to the pre-mRNA. May also be involved in the assembly of the 'E' complex. Belongs also to the minor U12-dependent spliceosome , which is involved in the splicing of rare class of nuclear pre-mRNA intron. ,PTM:Phosphorylated. Phosphorylation occurs concomitantly with the splicing catalytic steps. Phosphorylation on Thr-244 , Thr-248 and Thr-313 by cyclin-dependent kinases promotes interaction with PPP1R8 during mitosis. ,similarity:Belongs to the SF3B1 family. ,similarity:Contains 11 HEAT repeats. ,subcellular location:During mitosis , transiently dispersed from the nuclear speckles to the cytoplasm. ,subunit:Identified in the spliceosome C complex , at least composed of AQR , ASCC3L1 , C19orf29 , CDC40 , CDC5L , CRNKL1 , DDX23 , DDX41 , DDX48 , DDX5 , DGCR14 , DHX35 , DHX38 , DHX8 , EFTUD2 , FRG1 , GPATC1 , HNRPA1 , HNRPA2B1 , HNRPA3 , HNRPC , HNRPF , HNRPH1 , HNRPK , HNRPM , HNRPR , HNRPU , KIAA1160 , KIAA1604 , LSM2 , LSM3 , MAGOH , MORG1 , PABPC1 , PLRG1 , PNN , PPIE , PPIL1 , PPIL3 , PPWD1 , PRPF19 , PRPF4B , PRPF6 , PRPF8 , RALY , RBM22 , RBM8A , RBMX , SART1 , SF3A1 , SF3A2 , SF3A3 , SF3B1 , SF3B2 , SF3B3 , SFRS1 , SKIV2L2 , SNRPA1 , SNRPB , SNRPB2 , SNRPD1 , SNRPD2 , SNRPD3 , SNRPE , SNRPF , SNRPG , SNW1 , SRRM1 , SRRM2 , SYF2 , SYNCRIP , TFIP11 , THOC4 , U2AF1 , WDR57 , XAB2 and ZCCHC8. Component of splicing factor SF3B which is composed of at least eight subunits; SF3B1/SAP155/SF3B155 , SF3B2/SAP145/SF3B155 , SF3B3/SAP130/SF3B130 , SF3B4/SAP49/SF3B49 , SF3B14A , PHF5A/SF3B14B , SF3B10 and SF3B125.Component of the B-WICH complex , at least composed of SMARCA5/SNF2H , BAZ1B/WSTF , SF3B1 , DEK , MYO1C , ERCC6 , MYBBP1A and DDX21. SF3B associates with the splicing factor SF3A and a 12S RNA unit to form the U2 small nuclear ribonucleoproteins complex (U2 snRNP) . SF3B1 interacts directly with the splicing factor U2AF. Phosphorylated form interacts with PPP1R8. ,
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