Protein phosphatase that catalyzes the dephosphorylation of the C-terminal domain of RNA polymerase II. Plays a role in RNA processing and termination. Plays a role in pre-mRNA polyadenylation via its interaction with SYMPK. H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Interacts with GTF2B (via C-terminus); this interaction is inhibited by SYMPK. Interacts with RB1. Interacts with CD226. Interacts with SYMPK. Predominantly in the cytosol. Highly expressed in the brain. Expressed at low level in most tissues. At 10.5 dpc, low level expression detected throughout the embryo with relative accumulation in spinal cord and brain folds. At 13.5 dpc, highly expressed in the CNS both in the ventricular (mitotic) and marginal (post mitotic) zones, in the PNS in dorsal root and trigeminal ganglia, and the developing gut. During development, expression in the central nervous system and peripheral nervous system persists, and expression in the intestine is further induced. Expression in the intestine is observed throughout the mucosal villi, which contains epithelial cells and other cell types. High expression is also detected in the lens. No expression is seen in other tissues such as liver, lung, bone, cardiac and skeletal muscles. Belongs to the SSU72 phosphatase family.