Involved in the dephosphorylation of the large subunit of RNA polymerase II. Is required in late G1 for normal G1 cyclin expression, bud initiation and expression of certain genes that are periodically expressed during late G1. Associates with the SAP proteins in a cell cycle-dependent manner. H2O + O-phospho-L-seryl-[protein] = L-seryl-[protein] + phosphate H2O + O-phospho-L-threonyl-[protein] = L-threonyl-[protein] + phosphate Binds 2 manganese ions per subunit. Inactivated in a complex with phosphatase methylesterase PPE1 (PP2Ai). Interacts with phosphatase 2A activator RRD1, which can reactivate PP2Ai by dissociating the catalytic subunit from the complex. Forms a ternary complex with RRD1-TAP42. Functions in the late cell cycle G1 phase for progression into the S phase, possibly associated in two separate complexes with the phosphorylated forms of p155 and p190, two high MW proteins. Present with 3970 molecules/cell in log phase SD medium. Belongs to the PPP phosphatase family. PP-6 (PP-V) subfamily.