Unveiling the Cryo-EM Structures of PP2A:B55 Complexes with FAM122A and ARPP19

Cryo-EM structures of PP2A:B55–FAM122A and PP2A:B55–ARPP19 have been determined, shedding light on the molecular mechanisms of PP2A:B55 inhibition during mitotic entry. The structures reveal that ARPP19 and FAM122A bind to distinct regions of PP2A:B55, with ARPP19 binding in a tripartite manner involving three interaction sites. These findings provide valuable insights into the regulation of cell cycle progression and mitosis.