该基因编码剪接因子3b蛋白复合物的亚单位1。剪接因子3b与剪接因子3a和12s RNA单元一起形成u2小核核糖核蛋白复合物（u2 snrnp）。剪接因子3b/3a复合物以序列独立的方式结合内含子分支位点上游的pre-mRNA，并可能将u2 snrnp锚定到pre-mRNA。剪接因子3b也是小U12型剪接体的组成部分。亚基1的羧基末端三分之二具有22个不相同的串联热重复，形成棒状螺旋结构。选择性剪接导致编码不同亚型的多个转录变体。
This gene encodes subunit 1 of the splicing factor 3b protein complex. Splicing factor 3b, together with splicing factor 3a and a 12S RNA unit, forms the U2 small nuclear ribonucleoproteins complex (U2 snRNP). The splicing factor 3b/3a complex binds pre-mRNA upstream of the intron's branch site in a sequence independent manner and may anchor the U2 snRNP to the pre-mRNA. Splicing factor 3b is also a component of the minor U12-type spliceosome. The carboxy-terminal two-thirds of subunit 1 have 22 non-identical, tandem HEAT repeats that form rod-like, helical structures. Alternative splicing results in multiple transcript variants encoding different isoforms.