Regulator of type 1 phosphatases which maintains protein phosphatase activity under strict control. Regulates the nuclear localization of type 1 phosphatase GLC7 and SDS22, and is involved in the regulation of mRNA 3'-end processing. May also regulate the activity of type 1 phosphatase PPZ1. Interacts with GLC7, PPZ1 and SDS22. Present with 1080 molecules/cell in log phase SD medium. Belongs to the YPI1 family. Was originally (PubMed:14506263) thought to be an inhibitor of type 1 phosphatases using in vitro experiments, but further in vivo experiments (PubMed:18172024) showed that it was rather an activator of these phosphatases.