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.
Belongs to the SF3B1 family. Contains 11 HEAT repeats.
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.
Nucleus speckle. During mitosis, transiently dispersed from the nuclear speckles to the cytoplasm.