Protein phosphatase that dephosphorylates 'Ser-5' of the heptad repeats YSPTSPS in the C-terminal domain of the large RNA polymerase II subunit ama-1 (PubMed:26588990). By regulating the phosphorylation status of ama-1 and thus ama-1 binding to specific polyadenylation sites, regulates alternative polyadenylation of pre-mRNAs, including unc-44 and dlk-1 mRNAs (PubMed:26588990, PubMed:28087624). This results in the tissue-specific expression of unc-44 isoforms (PubMed:28087624). H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate May interact with synd-1 (via C-terminus); the interaction may prevent ssup-72 binding to RNA polymerase II ama-1 (PubMed:26588990). May interact with RNA polymerase II ama-1 (Probable). Expressed in epidermis, intestine and nervous system. Expressed in embryos, larvae and adults. May be phosphorylated by kin-20. Belongs to the SSU72 phosphatase family.