Involved in developmental cell fate decision. PP2A consists of a trimeric holoenzyme, composed of a 37 kDa catalytic subunit (C subunit) and a 65 kDa constant regulatory subunit (A subunit), that associates with a variety of regulatory subunits (B subunit) such as phr2AB (B55) and psrA (B56 homolog). The trimer may partially dissociates into a core 'AC' dimer equally active compared to the trimer. Seems to play a role in proper anterior patterning (pstO and pstAB). Null cells displays higher PP2A phosphatase activity compared with the wild type, around 10 hours of delayed expression of ecmA and ecmB prestalk markers, inefficient culmination and higher GSK3 kinase activity. Belongs to the phosphatase 2A regulatory subunit B56 family.