9c6b
PP2A:B55-p107 substrate complex
Structural highlights
Function2AAA_HUMAN The PR65 subunit of protein phosphatase 2A serves as a scaffolding molecule to coordinate the assembly of the catalytic subunit and a variable regulatory B subunit. Required for proper chromosome segregation and for centromeric localization of SGOL1 in mitosis.[1] Publication Abstract from PubMedPhosphoprotein phosphatases (PPPs) achieve specificity by binding substrates and regulators using PPP-specific short motifs. Protein phosphatase 2A (PP2A) is a highly conserved phosphatase that regulates cell signaling and is a tumor suppressor. Here, we use cryo-electron microscopy and nuclear magnetic resonance (NMR) spectroscopy to investigate the mechanisms of human p107 substrate and Eya3 regulator recruitment to the PP2A:B55 holoenzyme. We show that, while they associate with B55 using a common set of interaction pockets, the mechanism of substrate and regulator binding differs and is distinct from that observed for PP2A:B56 and other PPPs. We also identify the core B55 recruitment motif in Eya3 proteins, a sequence conserved amongst the Eya family. Lastly, using NMR-based dephosphorylation assays, we demonstrate how B55 recruitment directs PP2A:B55 fidelity through the selective dephosphorylation of specific phosphosites. As PP2A:B55 orchestrates mitosis and DNA damage repair, these data provide a roadmap for pursuing new avenues to therapeutically target this complex by individually blocking a subset of regulators that use different B55 interaction sites. Cryo-EM structures of PP2A:B55 with p107 and Eya3 define substrate recruitment.,Padi SKR, Godek RJ, Peti W, Page R Nat Struct Mol Biol. 2025 Apr 17. doi: 10.1038/s41594-025-01535-3. PMID:40247147[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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