該基因編碼剪接因子3b蛋白復合物的亞單位1。剪接因子3b與剪接因子3a和12s RNA單元一起形成u2小核核糖核蛋白復合物（u2 snrnp）。剪接因子3b/3a復合物以序列獨立的方式結合內含子分支位點上游的pre-mRNA，并可能將u2 snrnp錨定到pre-mRNA。剪接因子3b也是小U12型剪接體的組成部分。亞基1的羧基末端三分之二具有22個不相同的串聯熱重復，形成棒狀螺旋結構。選擇性剪接導致編碼不同亞型的多個轉錄變體。
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.