Acts as an inhibitor of serine/threonine-protein phosphatase 2A (PP2A) activity (PubMed:27588481, PubMed:33108758, PubMed:38123684). Inhibits PP2A activity by blocking the substrate binding site on PPP2R2A and the active site of PPP2CA (PubMed:38123684). Potentiates ubiquitin-mediated proteasomal degradation of serine/threonine-protein phosphatase 2A catalytic subunit alpha (PPP2CA) (PubMed:27588481). Inhibits PP2A-mediated dephosphorylation of WEE1, promoting ubiquitin- mediated proteolysis of WEE1, thereby releasing G2/M checkpoint (PubMed:33108758). {ECO:0000269|PubMed:27588481, ECO:0000269|PubMed:33108758, ECO:0000269|PubMed:38123684}. This is the function of PABIR1 (PP2A Aalpha (PPP2R1A) and B55A (PPP2R2A) interacting phosphatase regulator 1, ENSG00000187866).