Maintains the undifferentiated state of embryonic stem cells. By targeting the PR72/130 subunit of the Ser/Thr phosphatase PP2A, it prevents β-catenin from switching coactivator usage from CBP to p300. The increase in β-cateinin/CBP mediated transcription at the expense of β-cateinin/p300-mediated transcription helps to maintain the murine stem cell pluripotency.