TY - JOUR TI - PP2A/B55α substrate recruitment as defined by the retinoblastoma-related protein p107 AU - Fowle, Holly AU - Zhao, Ziran AU - Xu, Qifang AU - Wasserman, Jason S AU - Wang, Xinru AU - Adeyemi, Mary AU - Feiser, Felicity AU - Kurimchak, Alison N AU - Atar, Diba AU - McEwan, Brennan C AU - Kettenbach, Arminja N AU - Page, Rebecca AU - Peti, Wolfgang AU - Dunbrack, Roland L AU - Graña, Xavier A2 - Hahn, William C A2 - Cole, Philip A A2 - Malumbres, Marcos VL - 10 PY - 2021 DA - 2021/10/18 SP - e63181 C1 - eLife 2021;10:e63181 DO - 10.7554/eLife.63181 UR - https://doi.org/10.7554/eLife.63181 AB - Protein phosphorylation is a reversible post-translation modification essential in cell signaling. This study addresses a long-standing question as to how the most abundant serine/threonine protein phosphatase 2 (PP2A) holoenzyme, PP2A/B55α, specifically recognizes substrates and presents them to the enzyme active site. Here, we show how the PP2A regulatory subunit B55α recruits p107, a pRB-related tumor suppressor and B55α substrate. Using molecular and cellular approaches, we identified a conserved region 1 (R1, residues 615–626) encompassing the strongest p107 binding site. This enabled us to identify an ‘HxRVxxV619-625’ short linear motif (SLiM) in p107 as necessary for B55α binding and dephosphorylation of the proximal pSer-615 in vitro and in cells. Numerous B55α/PP2A substrates, including TAU, contain a related SLiM C-terminal from a proximal phosphosite, ‘p[ST]-P-x(4,10)-[RK]-V-x-x-[VI]-R.’ Mutation of conserved SLiM residues in TAU dramatically inhibits dephosphorylation by PP2A/B55α, validating its generality. A data-guided computational model details the interaction of residues from the conserved p107 SLiM, the B55α groove, and phosphosite presentation. Altogether, these data provide key insights into PP2A/B55α’s mechanisms of substrate recruitment and active site engagement, and also facilitate identification and validation of new substrates, a key step towards understanding PP2A/B55α’s role in multiple cellular processes. KW - serine-threonine phosphatase KW - PP2A KW - phosphorylation KW - enzyme KW - p107 KW - TAU JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -