an ubiquitous peptidyl-prolyl cis/trans isomerase. Distributed in nuclear speckles, which are rich in splicing factors. Colocalizes with the splicing factor SFRS2. A component of splicing factor complexes that bind the phosphorylated C-terminal domain (CTD) of RNA polymerase II. Interacts with CLK1 and PNN. Two splice variant isoforms of the human protein have been described. Note: This description may include information from UniProtKB.